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Revista del Museo Argentino de Ciencias Naturales

On-line version ISSN 1853-0400

Rev. Mus. Argent. Cienc. Nat. vol.23 no.1 Ciudad Autónoma de Buenos Aires June 2021

http://dx.doi.org/10.22179/revmacn.23.714 

ZOOLOGÍA

Redefinition of the identity and phylogenetic position of Tityus trivittatus Kraepelin 1898, and description of Tityus carrilloi n. sp. (Scorpiones; Buthidae), the most medically important scorpion of southern South America

Redefinición de la identidad y posición filogenética de Tityus trivittatus Kraepelin 1898, y descripción de Tityus carrilloi n. sp. (Scorpiones; Buthidae), la especie de mayor importancia mé dica del sur de Sudamérica

Andrés Alejandro Ojanguren Affilastro1  * 

John Kochalka2 

David Guerrero-Orellana2 

Bolívar Garcete-Barrett2 

Adolfo Rafael de Roodt3 

Adolfo Borges4 

F. Sara Ceccarelli5 

1 Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”. Av. Ángel Gallardo 470. Buenos Aires Argentina.

2 Museo Nacional de Historia Natural del Paraguay - Ministerio del Ambiente y Desarrollo Sostenible. San Lorenzo, Paraguay.

3 Área Investigación y Desarrollo-Venenos/Serpentario-Aracnario, Instituto Nacional de Producción de Biológicos ANLIS “Dr. Carlos G. Malbrán”, Ministerio de Salud. Argentina.

4 Centro para el Desarrollo de la Investigación Científica (CEDIC), Manduvirá 635 c/15 de agosto. Asunción, Paraguay.

5 Departamento de Biología de la Conservación, CONACYT-Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Carretera Ensenada-Tijuana No. 3918, Zona Playitas, C.P. 22860 Baja California, México.

Abstract

Tityus trivittatus is considered the most medically important scorpion species of southern South America. In this contribution we redefine its taxonomy, redescribe the species and separate the southern popula tions as a new species, Tityus carrilloi n. sp. As a consequence of this description, the most medically important species of the region turns out to be the new species herein described. We also clearly establish the phylogenetic position of both species through a dated molecular phylogenetic analysis based on four genes. Finally, we discuss the differences of the venom between the two species, and the epidemiologic implications of our results on the scorpionism problem in the region.

Keywords: Tityus; Taxonomy; Dated phylogeny; Scorpionism; South America

Resumen

Tityus trivittatus es considerada la especie de escorpión de mayor importancia médica en el sur de Sudamérica. En este trabajo redefinimos su taxonomía, redescribimos esta especie y sepa ramos las poblaciones meridionales como una nueva especie Tityus carrilloi n. sp. Como consecuencia de esta descripción, la especie de mayor importancia médica de la región es la especie que describimos aquí. Establecemos además claramente la posición filogenética de ambas especies a través de una filogenia molecular datada basada en cuatro genes. Finalmente discutimos las diferencias del veneno entre ambas especies y las implicaciones epide miológicas de nuestros resultados sobre el problema del escorpionismo en la región.

Palabras clave: Tityus; Taxonomía; Filogenia datada; Escorpionismo; Sudamérica

INTRODUCTION

The scorpion genus Tityus includes all med ically important species of southern South America, being responsible for several deaths ev ery year in this region (de Roodt et al., 2003, 2009, 2010, 2019; de Roodt, 2014; Ministerio de Salud, 2011; Docampo & Fernández, 2011; Blanco et al., 2016). Some of these species of medical im portance are parthenogenetic and synanthropic, which makes them extremely efficient invaders of human settlements (Toscano-Gadea, 2004; Lourenço, 2015). Thanks to this, many of them have largely expanded their distribution in the last years occupying most anthropized areas, re sulting in an increasingly complex scenario for the scorpionism problem in South America (Blanco et al., 2016; Ojanguren-Affilastro et al., 2019).

One of the first steps to develop health poli cies to deal with scorpionism should be to clearly establish the identity of the species of medical importance, so that the control strategies and antivenom production can be clearly focused to the correct target. This task however, has not been simple in South America, mostly due to the different criteria of different local specialists in species recognition, and the poor exchange of information between specialists of neighboring countries dealing with similar problems.

Due to its medical importance, Tityus is one of the most studied scorpion genera, but despite this, its taxonomy is far from being solved and has been revealed as one of the most complex genus in the order (Lourenço, 2006). Up to now, Tityus trivittatusKraepelin, 1898 is considered the most medically important scorpion species south of the 24º parallel in South America, with a distributional range occupying eastern Paraguay, southern Brazil, part of Uruguay, and especial ly, most of central and northern Argentina, in cluding all major cities of this country (Borges & Rojas de Arias, 2019; Ojanguren-Affilastro et al., 2019). Due to this, most control plans, and antivenom production for scorpions in Argentina were focused on this species (de Roodt, 2014; de Roodt et al., 2003, 2010; Ministerio de Salud, 2011).

In the framework of a collaborative research project between specialists of five different in stitutions of Argentina, Paraguay and Mexico, we have been able to revise a large amount of specimens currently considered as T. trivittatus, from all its distributional range, which led us to clearly establish the identity of this species. As a result, we could determine that T. trivittatus is restricted to the eastern part of Paraguay and a small part of Southwestern Brazil, whereas in Argentina and Uruguay the specimens current ly considered as T. trivittatus, actually belong to a different undescribed species. Therefore, the most medically important species of southern South America, turns out not to be T. trivitta tus but a new species that is described herein as Tityus carrilloi n. sp. In this contribution we also redescribe T. trivittatus and provide distribution maps of both species. We also provide a dated mo lecular phylogeny of the southernmost species of Tityus based on four genes, in which we included both studied species; therefore we provide infor mation on their phylogenetic position and rela tionships within the genus.

Finally, we provide a brief discussion about the different characteristics of their venoms and toxicity. Most of which has been described during the last years about the venom, antivenom, tox icity and lethality of T. trivittatus actually corre sponds to T. carrilloi n. sp. because most studies were carried out on Argentinean populations of this species (Coronas et al., 2003, 2015; de Roodt et al., 2001, 2010, 2019). Therefore, the taxonom ic changes herein presented, change the scenery of what is known about the scorpionism problem in the region. Due to the great medical impor tance of both herein studied species, we consid er it necessary to take the chance to provide an updated overview of the venom and toxicity of both species, considering for the first time each species separately.

On the identity of T. trivittatus

Tityus trivittatus was originally described based on two ♂ syntypes from San Salvador in Paraguay, by Kraepelin (1898). This locality does not correspond to the actual Paraguayan locali ty of San Salvador in the Department of Guairá, in southern Paraguay, because it was founded in 1951 and it didn’t exist in the nineteenth cen tury. The type locality corresponds to an old village, currently abandoned, which was placed approximately at 22°49’00’’S 57°47’00’’W, in the northern Department of Concepción, as stated by Maury (1970) and later by Lourenço (1980).

Shortly after the description of T. trivittatus, Borelli (1899) mistook it for T. carrilloi n. sp., and mentioned its presence in Argentina for the first time, in the province of Chaco. After that, several authors confused both species and re peatedly mentioned the presence of T. trivittatus in Argentina (see synonymic list), also extending its known distribution to other provinces.

The most influential paper of South American scorpiology of the twentieth century was the large monograph on South American scorpions by Mello-Leitão (1945); in that con tribution the author included a detailed draw ing of T. trivittatus, taken from his previous paper on the Argentinean scorpiofauna (Mello- Leitão, 1934), this figure clearly corresponds to an Argentinean specimen of T. carrilloi n. sp.. Additionally, he mentioned the presence of T. trivittatus in the city of Buenos Aires, confusing both species. After that, the presence of T. trivittatus in Argentina was assumed as correct by all posterior authors.

Maury (1970) was the first specialist who attempted to re-describe T. trivittatus with mod ern standards. He followed the widely accepted species concept of Mello-Leitão (1934, 1945), and based his work mostly in Argentinean specimens of T. carrilloi n. sp., therefore he also confused both species. Shortly after, Maury (1974) studied the types of Tityus confluens and Tityus trivitta tus, and separated both as valid species; in this period he also left an unpublished redescrip tion and drawings of the types of T. trivittatus (Maury unpublished data at Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” (MACN)). Lourenço (1980) also studied the syn types of T. trivittatus, provided a detailed draw ing of the pigment pattern of one of them, and briefly re-described the species; however this de scription partially follows the above mentioned Maury’s paper of 1970, therefore also confusing both species. More recently Maury (1997) pub lished an updated contribution on T. trivittatus, after revising a larger amount of specimens, in cluding the types of this species (as mentioned before); but still considering Argentinean speci mens of T. carrilloi n. sp. as T. trivittatus.

We have studied the scorpion collection of the Inventario Biológico Nacional de Paraguay (IBNP), which includes a large collection of T. trivittatus from all the country. Additionally, we have surveyed several localities of Paraguay, including some close to the type locality of this species. We have also studied a large amount of specimens from the MACN, assigned to T. trivittatus from Argentina, Brazil, Paraguay and Uruguay, and we have widely collected in north eastern Argentinean provinces in the border with Paraguay and Brazil, as well as in the south western Brazilian states. Due to all this, we have been able to study a large amount of specimens from all its distributional range, and found con spicuous and consistent differences in pigment pattern, external morphology, and hemisper matopohore morphology, between Paraguayan and Argentinean specimens, which clearly sep arate them as different species. We have also sequenced four molecular markers of specimens both, from Argentina and Paraguay, and per formed a molecular phylogeny, which clearly placed Paraguayan specimens of T. trivittatus as a different species from Argentinean specimens of T. carrilloi n. sp. which indeed is most closely related to Tityus confluensBorelli, 1899 (Fig. 1).

Fig. 1 Phylogenetic tree for the southernmost American species of Tityus with node age estimates inferred by BEAST. 95% Highest Posterior Density of node heights are shown by blue bars. Major clades are indicated on left of the tree. Time scale is indicated below the tree. 

We studied the unpublished description and drawings of the syntypes of T. trivittatus by E. Maury, and they clearly correspond to Paraguayan specimens, and not to Argentinean specimens. The pigment pattern of the figure of one syntype of Tityus trivittatus published by Lourenço (1980) also undoubtedly corresponds to the pigment pattern of Paraguayan speci mens. We have studied high quality photos of the best preserved syntype of this species kindly sent by Nadine Dupérré, curator of the Zoologischer Museum Hamburg (ZMH), and we could clearly observe the most important external diagnostic characters of the Paraguayan specimens, that separate them from the Argentinean specimens.

Due to all this we concluded that the Paraguayan specimens are conspecific with the syntypes of T. trivittatus, and that Argentinean specimens correspond to the species herein de scribed as T. carrilloi n. sp.

MATERIALS AND METHODS

Taxon Sampling

In this contribution we will accept the con cept of species groups and complexes used for the genus Tityus (Lourenço, 1979, 1980, 1981, 1982; Lourenço & Maury, 1985), but we will consider these subdivisions as synonyms, and in general refer to them as “complexes”. We will accept the sub-generic division of genus Tityus of Lourenço (2006). We will follow the generic group division of family Buthidae suggested by Fet et al. (2005). A priori we will consider all subgenera and gen era as monophyletic.

Most studied specimens belong to two dif ferent collections: Museo Argentino de Ciencias Naturales Arachnological collection (MACN-Ar, Martín Ramírez), Buenos Aires, Argentina; and the Inventario Biológico Nacional de Paraguay (IBNP, John Kochalka), Asunción, Paraguay. Since both herein studied species are synan thropic, most studied specimens for taxonomic studies were spontaneously deposited for iden tification by people in the above-mentioned in stitutions. Additionally, some specimens were manually collected by the authors at night using UV lamps, or during the day under stones, or logs. Licenses for legal collection were obtained in each case. For a list of the studied specimens of T. carrilloi n. sp. see Maury (1970, 1997); for a list of the studied specimens of T. trivittatus see Maury (1970, 1997) and Guerrero & Kochalka (2015).

Point locality records were georeferenced in the field with portable Global Positioning System devices (Garmin® GPS II Plus, Etrex, Etrex Vista and Etrex Vista C) or retroactively using the GeoNet Names Server (https://geonames. nga.mil/gns/html/). A distribution map was gen erated using the web site www.simplemappr.net.

Most sequenced terminals used in this anal ysis correspond to a previous contribution of two of the authors (Ojanguren-Affilastro et al., 2017a) with a phylogenetic study of southern most American Buthids. Additionally, we includ ed sequences of two specimens of T. trivittatus from Asunción, Paraguay. We have included all known species of Tityus from southern part of South America: Tityus argentinusBorelli, 1899, Tityus bahiensis (Perty, 1833), Tityus carrilloi n. sp., T. confluens, Tityus curupi Ojanguren- Affilastro, Adilardi, Cajade, Ramírez, Ceccarelli & Mola, 2017, Tityus paraguayensis Kraepelin, 1895, Tityus serrulatusLutz & Mello, 1922, Tityus trivittatus Kraepelin, 1898, and Tityus uruguayensis Borelli, 1901. We also included some data from related species available from nearby areas. From the subgenus Tityus we in cluded Tityus carvalhoiMello-Leitão, 1945, from southern Brazilian Cerrado. From the subgenus Archaeotityus we included Tityus mattogros sensis Borelli, 1901 from Southern Brazilian Cerrado, Tityus bastosi Lourenço, 1984 from tropical forests of Ecuador, and the type species of the subgenus Tityus clathratus Koch, 1845 from northern South America. From the boliv ianus group of the subgenus Tityus we included two Andean Bolivian species Tityus soratensis Kraepelin, 1912, and Tityus andinus Kraepelin, 1911. We also included some representatives be longing to subgenus Atreus from northern South America: Tityus nematochirus Mello-Leitão, 1940, Tityus pachyurus Pocock, 1897, Tityus perijanensis González-Sponga, 1994, and Tityus discrepans (Karsch, 1879). In total, we used 20 individuals belonging to 19 species of Tityus.

As outgroups we have included other three Buthids: Zabius birabeniMello-Leitão, 1938, from central Argentina, belonging to the Tityus group; Grosphus flavopiceus Kraepelin, 1900, from Madagascar, belonging to the Uroplectes group and Ananteris balzanii Thorell, 1891, from northern Argentina, belonging to the Ananteris group.

Sequences are deposited in GenBank (for ac cession numbers, see Appendix S1).

Taxonomy

Descriptive terminology follows Ojanguren- Affilastro (2005), Maury (1970) and Ojanguren- Affilastro et al. (2017b), for hemispermato phores. Vachon (1974) for trichobothria. Ochoa et al. (2010) for metasomal carinae, abbreviated as follows: DL: dorsolateral; LIM: lateral infra median; LSM: lateral supramedian; LM: lateral median; VSM: ventral submedian; VL: ventro lateral; VM: ventromedian. Prendini (2000) for pedipalp carinae, abbreviated as follows: DI: dorsal internal; DE: dorsal external; VI: ventral internal; SD: sub digital; VE: ventral external; D: digital; E: external; IM: internomedian; EM: externomedian; V: ventral; VM: ventral median; DM: dorsal marginal; DS: dorsal secondary.

Measurements were taken using an ocular micrometer and are expressed in mm. Digital images of pigmentation pattern and habitus were taken under visible light, whereas images of external morphology were taken under UV light; we used a digital camera (Leica DFC290 or Nikon DS-Fi1) attached to a stereomicroscope (Leica M165C or Nikon SMZ1500), and the focal planes fused with Helicon Focus 3.10.3 (http://helicon.com.usa/heliconfocus/).

DNA Sequencing, sequence alignment and phylogenetic analyses

As mentioned previously, most sequences used in this analysis correspond to a previous contribution of two of the authors (Ojanguren- Affilastro et al., 2017a). Additionally, we includ ed sequences of two specimens of T. trivittatus from Asunción, Paraguay, one from Borges et al. (2020a), and a specimen deposited in MACN-Ar (41603). DNA extraction, PCR amplification, and sequencing of the four gene fragments (COI, 16S rDNA, 28S rDNA and H3a) for an additional Tityus trivittatus specimen was carried out fol lowing the procedures described in Ojanguren- Affilastro et al. (2017a). The amplified fragments were sent for sequencing at Macrogen Inc., Korea. The new sequences were combined with sequences from the aforementioned taxa in a multiple alignment, substitution models select ed, and Bayesian phylogenetic analyses run by Markov Chain Monte Carlo (MCMC) simulation in MrBayes v 3.2.6 (Ronquist et al., 2012) and BEAST v. 1.10.4 (Drummond et al., 2012), as in Ojanguren-Affilastro et al. (2017a). For the node age estimates in BEAST, a rate of 0.0086 substitutions/myr was applied as the mean for a normal prior (with 0.001 standard deviation) of the uncorrelated lognormal clock rate for the COI fragment. These values were obtained from the phylogenetic analyses with calibrated nodes from Ojanguren-Affilastro et al. (2017a). Nodal support of the Bayesian phylogenies was as sessed based on posterior probabilities.

RESULTS

Taxonomy

Scorpiones C. L. Koch, 1850

Buthoidea Simon, 1879

Buthidae C. L. Koch, 1837

Tityus C. L. Koch, 1836

Tityus carrilloi n. sp. Ojanguren-Affilastro (Figs. 1-8)

Fig. 2 Map of southern South America, with known distribution of Tityus carrilloi n. sp. (shaded red) and Tityus trivittatus (shaded blue). Type locality of each species is marked by a black triangle and a black star respectively. Larger rivers of the region acting as a barrier for these species are also marked. 

Fig. 3 Tityus carrilloi n. sp. Habitus, A, B. Holotype ♂. C, D. Paratype ♀. A, C. Dorsal aspect. B, D. Ventral aspect. Scale bar: 10 mm. 

Fig. 4 A-C. Tityus carrilloi n. sp. A. Carapace ♂; B. Carapace ♀; C. Tergites, pigment pattern. D-F. Tityus trivittatus. D. Carapace ♂; E. Carapace ♀; F. Tergites, pigment pattern. Scale bars: 1 mm. 

Fig. 5 A-H. Tityus carrilloi n. sp. A-D. Left pedipalp chela, ♂. A. Dorsal aspect. B. External aspect. C. Ventral aspect. D. Internal aspect. E-H. Left pedipalp chela, ♀. E. Dorsal aspect. F. External aspect. G. Ventral aspect. H. Internal aspect. DI: dorsal internal; DE: dorsal external; VI: ventral internal; VE: ventral external; D: digital; E: external; IM: interno median; DS: dorsal secondary; SD: sub digital. Scale bars: 1 mm. 

Fig. 6 A-C. Tityus carrilloi n. sp. A. Sternites and pectines ♂; B. Sternites and pectines ♀; C. Tergites. D-F. Tityus trivittatus. D. Sternites and pectines ♂; E. Sternites and pectines ♀; F. Tergites. Scale bars: 10 mm. 

Fig. 7 A, B, E, G. Tityus carrilloi n. sp. A. Metasomal segment V, ♂, lateral aspect; B. Metasomal segment V ♀, lateral aspect; E. metasomal segments I-III, ♂, lateral aspect; G. Metasomal segment V, ♂,ventral aspect. C, D, F, H. Tityus trivittatus C. Metasomal segment V, ♂, lateral aspect; D. Metasomal segment V ♀, lateral aspect; F. metasomal segments I-III, ♂, lateral aspect; H. Metasomal segment V, ♂,ventral aspect. Scale bars: 1 mm. 

Fig. 8 A-E. Tityus carrilloi n. sp. A, B. Telson. A. ♀, lateral aspect. B. ♂, lateral aspect. C-E. left hemispermato phore. C. Internal aspect; d. detail of the lobe region and pars reflexa; E. Detail of the lobe region. Scale bars: 1 mm. 

Zoobank registration: http://zoobank.org/urn:lsid:zoobank.org:act:8C153A21-BD52-48A0- 9D50-6D4439B8E7D0

Type material: Holotype ♂: Argentina, Chaco province, Paraje La Armonia (29°09’14.28”S; 56°51’50.14”W), 11/X/2013, L. Damer coll., (MACN-Ar 41596). Paratypes: Argentina, Corrientes province: 3 ♀ Corrientes city (29º06’48.85’’S; 56º55’05.81’’W), 23/IX/1991, Varisco Coll. (MACN-Ar 41599); 1 ♂ Bella Vista, (28°33’47,31’’S; 59°02’32,70’’W), 10/ XI/1980, J. Williams coll. (MACN-Ar 41600). Chaco province: 1 ♂ Samuhu, (27°31’12,36’’S; 60°23’56,95’’W), II/1947, M. Biraben coll. (MACN-Ar 41601). Entre Ríos province: 3 ♀, Paraná city (31°44’45,27’’S; 60°30’57,77’’W), XI/1968, Paggi coll. (MACN-Ar 41602).

References: Tityus trivittatus: Borelli, 1899: 4-5 (part); Borelli, 1901: 5-6 (part); Mello-Leitão 1931: 128,129, 144 (part); Mello-Leitão, 1932: 17, 18, 29 (part); Mello-Leitão, 1934: 22, 23 (part); Mello-Leitão, 1938: 93-95 (part); Mello- Leitão, 1939a: 62, 64, 73 (part); Mello-Leitão, 1939b: 611(part); Mello-Leitão, 1945: 300, 364- 367 (part); Ábalos, 1959: 592; Ábalos, 1963: 113; Bucherl, 1964: 59 (part); Bücherl, 1969: 768 (part); Maury, 1970: 405-421(part); Bücherl, 1971: 327, 330, 332 (part); Maury, 1974: 89, 91 (part); Lourenço, 1980: 793-840 (part); Maury, 1986: 4, 10; Acosta, 1991: 11; Kovarik, 1992: 184; Peretti: 1994: 9-21; Acosta, 1995: 57; Acosta & Rosso de Ferradás, 1996: 84; Lourenço, 1997: 596 (part); Maury, 1997: 1-21 (part); Acosta & Maury, 1998: 559; de Roodt et al,. 2001: 99-109; Lourenço, 2001: 160, 161, 166 (part); Salomon & de Roodt, 2001: 391-396; Murúa et al., 2002: 75-78; de Roodt et al., 2003: 971-977; Toscano- Gadea, 2004: 866-869 (part); Ojanguren- Affilastro, 2005: 92-94 (part); Fernández- Campón & Lagos-Silnik, 2009: 219-221; de Roodt et al., 2010: 307-319; Docampo & Fernández, 2011: 16-18; Seiter, 2012: 117; Toscano-Gadea, 2012: 83, 86, 87 (part); Adilardi et al., 2014: 81- 88 (part); Coronas et al., 2015: 11-16; de Roodt, 2014: 1434-1452; de Roodt et al., 2014: 5-13; de Roodt, 2015: 55-71; Adilardi et al., 2015: 394; Guerrero & Kochalka, 2015: 62, 63, 64 (part); Blanco et al., 2016: 77-83; Carvalho et al., 2017: 1-6 (part.); de Roodt et al., 2017: 1-24; Faúndez & Albornoz, 2017: 165-166 (part.); Ojanguren- Affilastro et al., 2017a: 44, 45 (part.); Ojanguren- Affilastro et al., 2017b: 6, 11, 13 (part.); Ojeda & Neder, 2017: 12-22; Seiter & Stockmann, 2017: 155-158, 160-163 (part); Fernández et al., 2018: 12-18; Martínez et al., 2018: 62-72; Borges & Rojas de Arias, 2019: 27-35 (part); de Roodt et al., 2019: 5-13; López et al., 2019: 51-54; Ojanguren- Affilastro et al., 2019: 101, 102, 104, 105 (part.); Borges et al., 2020a: 2, 10, 15, 18, 21 (part).

Tityus trivittatus trivittatus: Mello-Leitão, 1945: 310 (part); Ringuelet, 1953: 278; Maury, 1970: 406-414 (part); 1974: 85, 89, 91 (part.); Lourenço, 1979: 37-45 (part); Maury, 1979: 705 (part); Lourenço, 1980: 797, 798, 839 (part.).

Etymology. This species is named after Ramón Carrillo, the first minister of health of Argentina as homage to his work for the Argentine public health. Ramón Carrillo was a neurobiologist and neurosurgeon, and was responsible for many advances in Argentine public health during his work as minister. He died exiled and in poverty in 1956 in Brazil at the age of 50.

Diagnosis and comparisons. A medium sized species of Tityus belonging to the trivittatus com plex and to the nominotypic subgenus.

Tityus carrilloi n. sp. is most closely related to T. confluens. Both species can be easily sepa rated by their pigmentation pattern. In T. carrilloi n. sp. tergites I-VI bear three pigment spots two lateral and one median (Fig. 4C), whereas in T. confluens tergites I-VI are completely covered by pigment.

Tityus carrilloi n. sp. is externally more similar to T. trivittatus with which it has been confused up to now; both species can be easily separated by their pigmentation pattern; both species bear three pigment spots on tergites I- VI forming three dark dorsal stripes, two later al and one median, however in T. carrilloi n. sp. the dark areas are comparatively narrower than the unpigmented areas; the median spot in is subtriangular, with one apex in the anterior mar gin, and one side on the posterior margin, being the whole spot uniformly and densely pigmented (Fig. 4C), whereas in T. trivittatus the median spot is almost squared, with an unpigmented median area, which in some cases is so large that it divides the square into two separated spots; the lateral spots are C shaped in both species, with an internal unpigmented area, being these pigmented spots narrower in T. carrilloi n. sp. and with a less developed internal unpigmented area (Fig. 4F). Most specimens of T. carrilloi n. sp. bear a median dorsal spot in pedipalp patella (Figs. 3A, C), as well as a ventromedian stripe in metasomal segments which are always absent in T. trivittatus (Figs. 9A, C).

There are other conspicuous somatical differ ences. The dorsal median carina of tergites I-VI is complete in T. carrilloi n. sp., ranging from the posterior margin to the transversal carina of the pretergite (Fig. 6C), whereas in T. trivittatus it is incomplete, usually occupying only the posterior half of the segment, barely exceeding its median double area (Fig. 6F). The LIM carina of metaso mal segment II occupies the entire length of the segment in T. carrilloi n. sp. (Fig. 7E), whereas in T. trivittatus it is absent or reduced to the pos terior third of the segment (Fig. 7F).

Additionally, there are less conspicuous dif ferences between species; T. carrilloi n. sp. tends to be less granular and slightly smaller than T. trivittatus. The pedipalp chela of T. carrilloi n. sp. males (Fig. 5B) is higher than that of T. trivittatus (Fig. 10B), but presents smaller internal lobe on the movable finger. Metasomal segment V of T. carrilloi n. sp. is higher and wider than in T. trivittatus, being this difference particularly conspicuous in males (Figs. 7A, C). Spiracles are narrower or more compressed anteroposteriorly in T. carrilloi n. sp. than in T. trivittatus (Figs. 6A, B, D, E). Basal lobe of the hemispermato phore is hook shaped in both species, but it has a wider internal concavity in T. carrilloi n. sp. Both internal and external lobes are more con spicuous in T. carrilloi n. sp. than in T. trivittatus (Figs. 8C, 11C).

Description. Based on the holotype ♂, and paratypes (MACN). Total length: 53.70-62.50 mm (n=4; mean=56.25) in ♂; 49.90-65.00 mm (n=10; mean=55.20) in ♀. Colour: Base colour yellowish, with dark brown pattern in chelicer ae, chelae, legs, carapace, tergites and metasoma (Figs. 3A, B, C, D). Chelicerae: light yellow with a dense reticulate pattern in manus and fingers, which can be faint in some specimens. Carapace: with black areas around ocular tubercle and lateral eyes; densely pigmented in the anterior and lateral margins, with a unpigmented area Y shaped from the posterior margin to the ocular tubercle. Tergites I-VI (Fig. 4C) each with three dark spots extending the entire length of the seg ment, two laterals, and a median dark spot; these spots are not connected to each other, leaving two wide unpigmented stripes, the median spot is subtriangular, with its anterior margin being acute and its posterior margin being the pos terior margin of the triangle; lateral sports are C shaped. Tergite VII only with a median elon gated subriangular stripe, with a wider anterior margin and a thin posterior margin. Sternites, sternum, genital opercula and pectines unpig mented. Metasomal segments I-III general yel lowish colour, dorsally with a thin median stripe along the dorsal median furrow, this stripe can be absent or faint in some specimens; lateral margins unpigmented; ventral margin with a median stripe occupying the area between VSM carinae, this stripe is usually well marked in juveniles, but in adults it is faint or irregularly marked in most specimens, being absent in some specimens. Metasomal segment IV general colour reddish, dorsally unpigmented or with an anteri or median faint pigment triangle occupying the posterior two thirds of the segment, ventrally as segments I-III. Metasomal segment V general colour reddish-brown, darker in males, ventrally some specimens with a thin dark stripe along the VM carina, the rest unpigmented. Telson, vesi cle general colour reddish, aculeus dark brown. Pedipalps: femur unpigmented or with a small postero-dorsal spot in the articulation with patel la; patella of most specimens with a brown spot covering most of the anterior, dorsal and poste rior margins, ventrally unpigmented; this spot can be absent in some specimens; chella manus unpigmented; fingers dark reddish brown. Legs: usually unpigmented, some specimens with a faint brownish pattern in the external margins of femur, patella, tibia and basitarsus.

Carapace. Anterior margin with a conspicu ous broad median notch that divides the anterior margin into two lobes. Surface densely granular. Anteromedian longitudinal sulcus, interocular sulcus; posteromedian longitudinal and lateral sulci present and conspicuous. Median ocular tubercle well developed, and clearly protruding above carapace in lateral profile; median ocel li well developed, approximately one diameter apart. Three small lateral ocelli on each side of carapace. Anterior median carinae, median ocu lar carinae, lateral carinae, and posterior carinae all granular and well developed (Figs. 4A, B).

Chelicerae. Tegument granular, especial ly near the distal margin, more so in males. Dentition typical for the genus. Teeth well de veloped.

Pedipalps. Femur, intercarinal surfaces densely granular except for the ventral surface which is barely granular, with smooth parts; DE, DI, VE and VI carinae granular and well devel oped, extending the entire length of the segment; internal margin with an interno-median (IM) ca rina extending the entire length of the segment. Patella intercarinal surfaces sparsely granular DI, DM, DE, IM VI, VE and EM carinae granu lar, extending the entire length of the segment, proximal granules of IM carinae are two or three times more developed than the rest. Chela manus slender, being more robust in ♂, length/height ra tio, ♀: 4.57-5.26 (N=10; mean=4.9), ♂: 3.73-4.15 (N=4; mean=3.99); length/width ratio, ♀: 4.79- 5.71 (N=10; mean=5.14), ♂: 3.86-4.40 (N=4; mean=4.16), DI, DE, DS, D, SD, E, VE, VI, and IM carinae granular and well developed, being the VI carina less developed in females (Figs. 5A-H); fixed and movable fingers thin, elongat ed and slightly curved internally; movable finger with 16, or 17, sub-parallel barely transversal denticle rows, being the basal row longitudinal basally and sometimes formed by the fusion of two denticle rows (Fig. 5A); fixed finger with 14 or 15 sub-parallel denticle rows, being the basal row longitudinal and always formed by the fu sion of two or three denticles rows (Fig. 5C); each of these denticles rows presents and apical en larged tooth and two basal enlarged teeth, which are two or three times bigger than the rest of the denticles; the apical enlarged tooth presents a hyaline and a chitinized seta at its base; the most apical of the basal enlarged denticles presents a single hyaline seta at its base, and the most basal presents a chitinized setae in its base; at the api cal margin of each finger there is an apical tooth with two lamellar, and two wide setae surround ing its basal margin. Movable finger with a basal lobe poorly developed in ♂ (Figs. 5B, D), absent or inconspicuous in ♀ (Figs. 5F, H); fixed finger straight in ♀, with a small shallow notch facing the basal lobe in ♂. Trichobothrial pattern ortho bothriotaxic type A; femur with 11 trichobothria, α configuration and trichobothria d2 placed on the internal surface; patella with 13 trichoboth ria; chela with 15 trichobothria, being esb petit.

Legs. Intercarinal surfaces finely granular. Carinae granular, extending the entire length of the segment. Basitarsi each with two well de veloped, equal-length pedal spurs; the external one presents an external, very well developed, macroseta. Telotarsi short, ventrally with abun dant chitinized setae, and some VL hyaline setae with following counts, on legs I to III: 4/3, IV: 5/4. Pseudoniquium elongated. Ungues well de veloped, equal in length and curved.

Sternum. Sub-triangular.

Genital opercula. Medium sized. Sclerites with a general subtriangular shape but with a curved anterior margin, in ♀ the posterior mar gin of the sclerites is also curved whereas in ♂ it is almost straight and perpendicular to the axis of the body.

Pectines. With a single row of median lamel lae; first median lamella nearly similar in size in ♂ and ♀ (Figs. 6A, B). Fulcra present, small and subcircular. Pectinal teeth medium sized; tooth count: 20-22 in ♂ (n= 4; median = 21), 19-21 in ♀ (n = 10; median = 21).

Tergites. Pretergites with fine granulation, separated from the rest of the tergite by a well developed anterior transversal carina. Tergites I-VI, surfaces granular being more coarse so in the posterior half of the segment, with a barely visible incomplete transversal carinae separat ing anterior and posterior halves of each tergite; with a dorsal-median longitudinal carinae ex tending from the posterior margin to the base of the pretergite (Fig. 6C); the dorsal median carina is formed posteriorly and anteriorly by a single row of granules that becomes double in its me dian part; with two very small dorso-submedian carinae barely protruding from the pretergite transversal carina, being more conspicuous in the posterior segments; posterior margin more densely granular, almost forming a posterior transversal carina. Tergite VII surfaces granu lar, dorsal-median carina extending the anterior two thirds of the segment, formed by a double row of granules in its anterior half, fusing in a single row in the second half; with four longi tudinal dorso-submedian carinae extending the entire length of the segment, fusing anteriorly to each other in a subcircular transversal carina, that also fuses in its anterior margin with the transversal carina of pretergite.

Sternites. Sternite I finely granular near the lateral margins, with two VSM semi-transversal furrows joining near the anterior margin and surrounding a glandular subtriangular area, this gland is also delimitated by two carinae and a row of setae forming a triangular shape; this gland is more conspicuous in males than in females (Figs. 6A, B); with small, elliptical narrow or an tero-posteriorly compressed spiracles. Sternite II: tegument finely granular, with a transversal row of four setae and one seta near each spir acle; with two small VSM furrows, with small, elliptical narrow spiracles. Sternite III: similar to II but with a well developed posteromedian subtriangular gland, more conspicuous in males. Sternite IV: similar to II but with two VSM lon gitudinal carinae occupying slightly more than the posterior half of the segment. Sternite V: tegument granular, with four longitudinal VSM carinae (Figs. 6A, B), the external carinae are placed in the median part of the segment occu pying slightly more than a half of the segment, the internal carinae are longitudinal and occupy almost the whole segment, presenting a small curve in the anterior third surrounding a mac roseta; in some specimens there is also a poorly developed VM carina in the anterior third of the segment.

Metasoma. Metasomal segment I: intercari nal surfaces finely granular; DL, LSM, LIM, VL and VSM carinae granular end extending the entire length of the segment; distal granules of the DL carinae of the same size and shape as the rest (Fig. 7E). Segment II similar to segment I but LIM carina is less developed, presenting fewer granules. Segments III and IV similar to segment II but the LIM carina becomes less developed in each segment, being absent or inconspicuous in segment IV; dorsally with a smooth median area, being more conspicuous in ♀. Segment V, slightly more elongated than the rest of the segments, being oval shaped (Figs. 7A, B, G), being clearly higher and wider in ♂ than in ♀ (Figs. 7A, B, G), length/height ratio, ♀: 2.12-2.33 (N=10; mean=2.22), ♂: 2.03-2.10 (N=4; mean=2.07); length/with ratio, ♀: 2.12- 2.28 (N=10; mean=2.19), ♂: 1.97-2.10 (N=4; mean=2.02), dorsolateral margin with a well de veloped carina, VL and VM carinae granular and extending the entire length of the segment (Fig. 7G); with poorly developed VSM carinae, formed by tiny granules, but extending almost the entire length of the segment.

Telson. Vesicle oval, with the dorsal surface flatter in ♀ and slightly convex in ♂ (Figs. 8A, B). Surface granular, with a poorly developed VM carina, and barely visible lateral carinae; with some scattered setae. Subaculear tubercle sub pyramidal, ventral margin smoothly serrat ed and connecting to the VM carina, base of the dorsal margin with two small but conspicuous and well separated granules. Aculeus strongly curved, basal part of the ventral margin with a well developed furrow.

Hemispermatophore. flageliform, typical of the subgenus. Slender (Figs. 8C, D, E). Pars re flexa poorly developed and highly curved, pars recta well developed and slightly curved medi ally. Lobe region well developed, internal lobe short, basal lobe hook-like, external lobe well developed, triangular, clearly separated from the hemispermatophore, median lobe small, barely protruding (Figs. 8C, D).

Distribution, ecology and synanthrop ic populations. Tityus carilloi n. sp. occupies most parts of central and northern Argentina (Fig. 2). However, most of its distribution corre sponds exclusively to synanthropic, parthenoge netic all-female populations, and not to records in nature. With the available and historic data we can assume that the original distribution of this species, corresponds to the area in which males and females can be found in natural envi ronments, and that the synanthropic partheno genetic populations are the result of a relatively recent process of invasion of this species into hu man settlements in the last century (Adilardi et al., 2014; Ojanguren-Affilastro et al., 2019).

The original distributional area of T. carril loi n. sp. seems to be restricted to a relatively small range of humid Argentinean Chaco, proba bly limited northerly by the Bermejo River (Fig. 2). Some all-female populations can be found in the wild in a slightly larger area of humid Argentinean Chaco, and we consider that this area could probably correspond to the original natural distribution of this species too. In both areas, also synanthropic all female parthenoge netic populations can be found.

Males of this species are remarkably scarce; we have had access to only four of them (among hundreds of specimens examined), each from a different population, from Chaco and Corrientes provinces, as well as to an old specimen from Buenos Aires, surely mislabeled (Maury, 1970). Additionally, a sexual population of this species has been cited from an area near the city of Corrientes (Seiter & Stockman, 2017).

The invasive capability of T. carrilloi n. sp. is remarkable since the use of human settlements allowed this species to reach areas with com pletely different climates from those from where it originated. Due to the progression in the stud ies on this species performed during the last 70 years by different authors in Argentina, we know that it has extended its distribution about 300% in this period (Mello-Leitão, 1934, 1945; Maury, 1970; 1997; Murúa et al., 2002; Fernández- Campón & Lagos Silnik, 2009; Ojeda & Neder, 2017; Ministerio de Salud, 2011; Ministerio de Salud Pública de la Provincia de Salta, 2011; Ojanguren-Affilastro et al., 2019; López et al., 2019). Most certainly this species has been pas sively transported by humans to all the cities out of the area of its original distribution.

Considering both natural and synanthrop ic populations, the distribution of this spe cies seems to be restricted northerly by the Pilcomayo, Paraguay, and Paraná Rivers, reach ing the northernmost part of Argentina in Jujuy, Salta, Formosa and Misiones provinces (Ojanguren-Affilastro et al., 2019). Apparently, it is not present yet in Bolivia, Paraguay, nor in Brazil; however due to its tremendous capabili ty to expand by invading human settlements, its current presence or future colonization, in these countries as a synanthropic species cannot be ruled out. Westerly, this species has invaded cities placed in desert sub-Andean areas of Argentina, where the genus Tityus is not naturally pres ent (Murúa et al., 2002; Fernández-Campón & Lagos Silnik, 2009). However, it has not crossed the Andes mountain chain yet, which marks the Argentinean-Chilean border. The southernmost records of this species belong to Buenos Aires and La Plata cities (latitude: 34º50’S), being also the southernmost populations of a danger ous scorpion in the world, together with the re cently arrived sympatric T. confluens (de Roodt et al., 2009; Ojanguren-Affilastro et al., 2019). This area presents a temperate climate, with temperatures in winter that can often reach 0º Celsius; being very different to the subtropical Chaco where T. carrilloi n. sp. belongs. Due to this, during the colder period of the year, these southernmost populations are restricted to the underground structures of the city (subways, basements, sewers etc.), which preserve a warm er temperature even in winter; only during the summer this species appears at the surface in the city. This dependence on a warmer underground in winter, has restricted the distribution of this species in this latitude to highly urbanized areas, not being present in the outskirts of the city.

Outside Argentina, T. carrilloi n. sp. is only present in Uruguay. The Uruguay River seems to be a natural barrier for this species, and most probably it has been recently introduced there from Argentina. All known records in this country belong to the area close to the city of Colonia de Sacramento (Toscano-Gadea, 2012), in Southwestern Uruguay, which is probably the most important port between Argentina and Uruguay.

Tityus trivittatusKraepelin, 1898

(Figs. 1, 2, 4, 6, 7, 9-11)

Fig. 9 Tityus trivittatus. Habitus, A, B. ♂. C, D. ♀. A, C. Dorsal aspect. B, D. Ventral aspect. Scale bar: 10 mm. 

Fig. 10 A-H. Tityus trivittatus. A-D. Left pedipalp chela, ♂. A. Dorsal aspect. B. External aspect. C. Ventral as pect. D. Internal aspect. E-H. Left pedipalp chela, ♀. E. Dorsal aspect. F. External aspect. G. Ventral aspect. H. Internal aspect. Scale bars: 1 mm. 

Fig. 11 A-E. Tityus trivittatus. A, B. Telson. A. ♀, lateral aspect. B. ♂, lateral aspect. C, D. left hemispermato phore. C. Internal aspect; D. detail of the lobe region and pars reflexa, lateral aspect; E. Right hemispermato phore, detail of the lobe region and pars reflexa, internal aspect. Scale bars: 1 mm. 

Tityus trivittatusKraepelin, 1898: 43-44. Type material: 2 syntypes ♂, Paraguay, San Salvador (ZMH).

References. Tityus trivittatus: Borelli, 1899: 4-5 (part); Kraepelin, 1899: 74, 83; Borelli, 1901: 5-6 (part); Kraepelin, 1901: 269; Werner, 1902: 600; Kraepelin, 1908: 193; Penther, 1913: 240; Lutz & Mello, 1922: 5,8; Mello-Campos, 1924a: 270; Mello-Campos, 1924b: 336; Mello-Leitão, 1931: 128,129, 144 (part); Mello-Leitão, 1932: 17, 18, 29 (part); Toledo-Piza, 1932: 302; Mello- Leitão, 1934: 22, 23 (part); Mello-Leitão, 1938: 93-95 (part); Mello-Leitão, 1939a: 62, 64, 73; Mello-Leitão, 1939b: 611; Mello-Leitão, 1945: 300, 364-367; Weidner, 1959: 104; Bucherl, 1964: 59 (part); Bücherl, 1969: 768 (part); Maury, 1970: 405-421(part); Bücherl, 1971: 327, 330, 332 (part); Maury, 1974: 89, 91 (part); Lourenço, 1980: 793-840 (part); Lourenço, 1982: 1-4; Maury, 1984: 216; Lourenço, 1994: 680, 681; Lourenço, 1997: 596 (part); Maury, 1997: 1-21 (part); Kovarik, 1998: 122. Lourenço, 2001: 160, 161, 166 (part); Toscano-Gadea, 2004: 866-869 (part); Ojanguren-Affilastro, 2005: 92-94 (part); Lourenço, 2006: 60; Toscano-Gadea, 2012: 83, 86, 87 (part); Adilardi et al., 2014: 81-88 (part); Guerrero & Kochalka, 2015: 62, 63, 64 (part); Carvalho et al., 2017: 1-6 (part.); Faúndez & Albornoz, 2017: 165, 166 (part.); Ojanguren- Affilastro et al., 2017a: 44, 45 (part.); Ojanguren- Affilastro et al., 2017b: 6, 11, 13 (part.); Seiter & Stockmann, 2017: 155-158, 160-163 (part); Borges & Rojas de Arias, 2019: 27-35 (part); Ojanguren-Affilastro et al., 2019: 101, 102, 104, 105 (part.); Borges et al., 2020a: 2, 10, 15, 18, 21 (part).

Tityus trivittatus trivittatus. Mello-Leitão, 1945: 310 (part); Bücherl, 1959: 260; Maury, 1970: 406-414 (part); Maury, 1974: 85; 89, 91 (part.); Bücherl, 1978: 372; Lourenço, 1979: 37-45 (part); Maury, 1979: 705 (part); Lourenço, 1980: 797, 798, 839 (part.).

Diagnosis and comparisons. A medium sized species of Tityus belonging to the trivittatus complex and to the nominotypical subgenus. Tityus trivittatus is most closely related to T. carrilloi and T. confluens. Tityus trivittatus can be separated from T. confluens by their pigmenta tion pattern. In T. trivittatus tergites I-VI bear three pigment spots two lateral and one median, whereas in T. confluens tergites I-VI are com pletely covered by pigment. To see the diagnostic characters separating T. trivittatus from T. car rilloi n. sp. see the diagnosis of this species.

Redescription. Based on the syntypes (ZMH), and material from the IBNP and MACN. Total length: 53.00-66.00 mm (n=9; mean=57.00) in ♂; 55.00-66.50mm (n=5; mean=63.50) in ♀.

Colour: Base colour yellowish, with dark brown pattern in chelicerae, carapace and tergites (Figs. 9A-D). Chelicerae: light yellow with a dense re ticulate pattern in manus and movable finger. Carapace: with black areas around ocular tuber cle and lateral eyes; with a dark triangle ranging from the posterior margin of the ocular tubercle to the frontal margin; lateral areas with dark re ticular pattern connecting with two posterolat eral dark spots and surrounding a median area almost devoid of pigment. Tergites I-VI (Fig. 4F) each with three dark spots extending the entire length of the segment, two lateral, and a medi an dark spot; these spots are not connected to each other, leaving two relatively narrow unpig mented stripes, the median spot is generally sub quadrangular, but in some specimens tends to be subtriangular; in all cases this spot presents a median unpigmented area, which in some cases divides the median spot into two separated spots; lateral spots C shaped, but usually with some re ticular pigment in its median area. Tergite VII only with a median elongated subtriangular stripe, with a wider anterior margin and a thin posterior margin. Sternites, sternum, genital opercula and pectines unpigmented. Metasomal segments I-IV general colour yellowish, without any pigment pattern. Metasomal segment IV general colour reddish, without any pigment pat tern. Telson, vesicle general colour reddish, ac uleus dark brown. Pedipalps: femur and patella unpigmented; chela manus unpigmented; fingers reddish brown (Fig. 9A-D). Legs: unpigmented.

Carapace. Anterior margin with a conspicu ous broad median notch that divides the anterior margin into two lobes. Surface densely granular, more so in the lateral margins. Anteromedian longitudinal sulcus shallow; interocular sulcus, posteromedian, longitudinal, and lateral sulci present and conspicuous. Median ocular tuber cle well developed and clearly protruding above carapace in lateral profile; median ocelli well developed, approximately one diameter apart. Three small lateral ocelli on each side of cara pace. Anterior median carinae, median ocular carinae, lateral carinae, and posterior carinae all granular and well developed (Figs. 4D, E).

Chelicerae. Tegument densely granular, espe cially near the distal margin, more so in males. Dentition typical for the genus. Teeth well de veloped.

Pedipalps. Femur, intercarinal surfaces densely granular except for the ventral surface which is barely granular. With smooth parts; DE, DI, VE and VI carinae granular and well developed, extending the entire length of the segment; internal margin with a well developed internal-median (IM) carina extending the en tire length of the segment. Patella intercarinal surfaces sparsely granular DI, DM, DE, IM VI, VE and EM carinae granular, extending the entire length of the segment, proximal two or three granules of IM carinae are approximately twice bigger than the rest. Chela manus slen der, being more robust in ♂, length/height ratio, ♀: 4.78-5.57 (N=5; mean=5.19), ♂: 3.85-4.31 (N=9; mean=4.14); length/width ratio, ♀: 5.19- 5.57 (N=5; mean=5.36), ♂: 3.85-4.31 (N=9; mean=4.14), DI, DE, DS, D, SD, E, VE, and IM carinae granular and well developed, VI carina granular but less developed (Figs. 10A-H); fixed and movable fingers thin, elongated and slight ly curved internally; movable finger with 16, or 17, sub-parallel barely transversal denticle rows (Fig. 10A), being the basal row longitudinal ba sally and sometimes formed by the fusion of two denticle rows; fixed finger with 14-16 sub-paral lel denticle rows (Fig. 10C), being the basal row longitudinal and always formed by the fusion of two or three denticles rows; each of these denti cles rows presents an apical enlarged tooth and two basal enlarged teeth, which are two or three times bigger than the rest of the denticles; the apical enlarged tooth presents one hyaline and one chitinized seta in the base of it; the most apical of the basal enlarged denticles presents a single hyaline seta in its base, and the most bas al presents a chitinized seta in its base; at the apical margin of each finger there is an apical tooth with two lamellar, and two wide setae sur rounding its basal margin. Movable finger with a basal lobe well developed in ♂ (Figs. 10B, D), absent or inconspicuous in ♀ (Figs. 10F, H); fixed finger straight in ♀, with a small notch facing the basal lobe in ♂. Trichobothrial pattern orthobo thriotaxic type A; femur with 11 trichobothria, α configuration and trichobothria d2 placed on the internal surface; patella with 13 trichobothria; chela with 15 trichobothria, being esb petit.

Legs. Intercarinal surfaces finely granular. Carinae granular, extending the entire length of the segment. Basitarsi each with two well devel oped, equal-length pedal spurs; the external one is bicuspid and presents an external very well developed macroseta. Telotarsi short, ventrally with abundant chitinized setae and 3/3 VL hy aline setae. Pseudoniquium elongated. Ungues medium sized, equal in length and poorly curved.

Sternum. Sub-triangular, being slightly wider in females.

Genital opercula. Medium sized. Sclerites with a general subtriangular shape but with a curved anterior margin, in ♀ the posterior mar gin of the sclerites is also curved, whereas in ♂ it is almost straight and perpendicular to the axis of the body.

Pectines. With a single row of median lamel lae; first median lamella more or less similar in size in ♂ and ♀ (Figs. 6D, E). Fulcra present, small and subcircular. Pectinal teeth medium sized; tooth count: 19-23 in ♂ (n= 9; median= 21), 19-21 in ♀ (n= 5; median= 20).

Tergites. Pretergites with fine granulation in ♂, more densely granular in ♀, separated from the rest of the tergite by a well developed ante rior transversal carina. Tergites I-VI, surfaces granular being more coarse so in the posterior half of the segment, with a barely visible in complete transversal carina separating anterior and posterior halves of each tergite; with a dor sal-median longitudinal carina extending from the posterior margin to the median part of the tergite, not reaching the pretergite (Fig. 6F); the dorsal median carina is formed by a single row of granules in the posterior margin of the segment, and becomes double in the median part of the tergite; the dorsosubmedian carinae are not con spicuous, being represented by small keels barely protruding from the pretergite transversal cari na in posterior segments, or by a single posterior granule in anterior segments; posterior margin with some coarse sparse granules. Tergite VII surfaces granular, dorsal-median carina extend ing the median half of the segment, not reaching the pretergite nor the posterior margin, formed by a double row of granules in its anterior half, fusing in a single row in the second half; with four longitudinal dorsosubmedian carinae ex tending the entire length of the segment, fusing anteriorly to each other in a subcircular trans versal carina, that also fuses in its anterior mar gin with the transversal carina of pretergite.

Sternites. Sternite I granular, with two VSM semi-transversal furrows joining near the ante rior margin and surrounding a glandular sub triangular area, this gland is also delimitated by a carina, less developed in ♂, and a row of se tae, all forming a triangular shape; this gland is more conspicuous in males than in females (Figs. 6D, E); with elliptical spiracles. Sternite II: tegument finely granular, with a transversal row of four setae and one seta near each spira cle; with two small VSM furrows joining anteri orly in the presternite transversal carina, and forming a semicircle, with elliptical spiracles. Sternite III: similar to II but with a well devel oped posteromedian, subtriangular gland, more conspicuous in males. Sternite IV: similar to II but with two VSM longitudinal carinae occupy ing slightly more than the posterior half of the segment. Sternite V: tegument granular, with four longitudinal VSM carinae (Figs. 6D, E), the external carinae are placed in the median part of the segment occupying slightly more than a half of the segment, the internal carinae are longi tudinal and occupy almost three quarters of the segment, being double in the anterior margin, surrounding a macroseta.

Metasoma. Metasomal segment I: interca rinal surfaces finely granular; DL, LSM, LIM, VL and VSM carinae granular end extending the entire length of the segment; distal gran ules of the DL carinae equal in size and shape as the rest. Segment II similar to segment I but LIM carina is very reduced, usually restricted to some granules in the posterior third of the seg ment (Fig. 7F). Segments III and IV similar to segment II but the LIM carina is absent, and the DL carina fuses posteriorly with the LSM cari na; dorsally finely granular. Segment V, slightly more elongated than the rest of the segments, being oval shaped, being higher and wider in ♂ than in ♀ (Figs. 7C, D, H), length/height ratio, ♀: 2.23-2.35 (N=5; mean=2.31), ♂: 2.03-2.28 (N=9; mean=2.15); length/with ratio, ♀: 2.12- 2.28 (N=5; mean=2.20), ♂: 2.00-2.21 (N=9; mean=2.10); surface densely granular, dorso lateral margin with a poorly developed but com plete carina, VL and VM carinae granular and extending the entire length of the segment (Fig. 7H); with barely visible VSM carinae, formed by tiny granules, but extending almost the entire length of the segment.

Telson. Vesicle oval, with the dorsal surface flatter in ♀ and slightly convex in ♂ (Figs. 11A, B). Surface granular, with a poorly developed VM carina, and barely visible lateral carinae; with some scattered setae. Subaculear tubercle subpyramidal, ventral margin smoothly serrat ed and connecting to the VM carina, base of the dorsal margin with two small but conspicuous and well separated granules. Aculeus strongly curved, basal part of the ventral margin with a well developed furrow.

Hemispermatophore. flageliform, typical of the subgenus. Slender (Fig. 11E). Pars reflexa poorly developed and highly curved, pars recta well developed and slightly curved medially. Lobe region well developed, internal lobe short, bas al lobe hook-like, external lobe well developed, triangular, clearly separated from the hemisper matophore, median lobe small, barely protruding (Figs. 11C, D).

Distribution and Ecology. Tityus trivitta tus occurs in a relatively wide region of east ern Paraguay and southern Brazil, in a mosaic of environments of wet Chaco, Cerrado and Atlantic Forest, (with a predominance of the first). This is also a synanthropic species, being common in the city of Asunción, where it is sym patric with T. confluens (Guerrero & Kochalka, 2015; Borges & Rojas de Arias, 2019). Its dis tributional limits seem to be represented by the Pilcomayo, Paraguay and Paraná rivers, in south, east and west of its distribution (Fig. 2); the northernmost limit of this species is not yet clearly established, but northernmost records are approximately at 17ºS in latitude (Maury, 1970; Lourenço, 1980; Carvalho et al., 2017). Up to now this species has not been collected in Argentina, where it is most certainly not pres ent in natural environments; however due to its synanthropic capabilities, it could be passively introduced in Argentina as some specimens of T. serrulatus (Camargo & Ricciardi, 2000; López et al., 2019). Contrary to T. carrilloi n. sp. all, nat ural and synanthropic populations of this species have both, males and females in similar propor tions, and up to now we have not found evidences of parthenogenetic populations of T. trivittatus.

Table 1 Measurements (mm) of Tityus carrilloi n. sp. (holotype ♂ and paratype ♀, MACN), and Tityus trivittatusKraepelin, 1898 (♂ and ♀, IBNP). 

Dated phylogenetic analysis

The split between T. trivittatus, from T. carrilloi n. sp., and T. confluens, occurred about 3.1 million years ago (mya; 0.5-5.6, 95% Highest Posterior Density - HPD), whereas the split be tween T. confluens and T. carrilloi occurred more recently, about 2.4 mya (0.6-4.4, 95% HPD) (Fig. 1) (Appendix S2).

In our analysis Tityus carrilloi n. sp. appears as more closely related to T. confluens than to T. trivittatus, with which it has been mistaken.

As expected, Tityus trivittatus is nested inside the trivittatus complex (Ojanguren-Affilastro et al., 2017a); however, it has to be taken in con sideration that this group was actually mostly based in T. carrilloi n. sp., which up to now was confused with T. trivittatus.

DISCUSSION

On the Chacoan origin of T. carrilloi n. sp., T. trivittatus and T. confluens

As stated in a previous contribution (Ojanguren-Affilastro et al., 2017a), the diversifi cation process of the Chacoan species of the trivittatus complex is congruent with the last retro gression of the Paranaense sea, that occupied the south-central area of South America between 20 and five mya (Donato et al., 2003). Most part of the emerged large areas of land that appeared af ter the retrogression of this sea in late Pliocene, were eventually occupied by the actual Chaco. All southern species of the trivittatus complex are closely related to northern species of the nomi notypical subgenus (Fig. 1), and seem to have evolved after dispersal in these recently emerged lands following a northern-southern pattern of distribution through the Chaco-Cerrado- Caatinga corridor (Lourenço 1986; Ojanguren- Affilastro et al., 2017a). A similar contemporary process through the same corridor has also been observed in Chacoan species of genera Ananteris and Zabius (Ojanguren-Affilastro et al., 2017a). On the other hand, Chacoan species of Bothriurid genus Brachistosternus Pocock, 1893 also settled in this area more or less in the same period, but following a different Andean route (Ceccarelli et al., 2016; Ojanguren-Affilastro et al., 2015).

The distribution of T. trivittatus and T. car rilloi n. sp. in relatively similar environments of Humid Chaco, but clearly separated by the large rivers of the region, is congruent with a process of allopatric speciation, in which these rivers could have acted as vicariant barriers. Tityus confluens on the other hand, occurs, in general, more west erly than the above-mentioned species, mostly in areas of dry Chaco, where it seems to have orig inated. Records of this species in sympatry with T. trivittatus and T. carrilloi n. sp. in anthropized areas seem to be due to recent colonization of T. confluens as a synanthropic species (Ojanguren- Affilastro et al., 2019).

Epidemiologic implications of the descrip tion of T. carrilloi n. sp., and characteris tics of the venom of T. carrilloi n. sp. and T. trivittatus

The description of T. carrilloi as a new separate species from T. trivittatus, despite being by far, the most studied scorpion species of its area of influence, reveals the important gaps that still occur in South American scorpion knowledge. Additionally, it reveals how some misconceptions can be established and sustained through time when there are no further re-evaluations of the available data.

The scorpionism problem due to T. carilloi n. sp. and T. trivittatus, from now on should be con sidered separately, taking into consideration the biological and phylogenetic differences between species.

Tityus carrilloi n. sp. The toxicity of the ven om of T. carrilloi n. sp. is clinically similar in human envenoming (de Roodt et al. 2003), and experimental envenomation (de Roodt et al., 2001, 2010), to those described for other Tityus species of the nominotypical subgenus of san itary importance. Its toxicity is in the range of that described for other closely related species; toxicity in 20g mice is around 0.6 μg/g, but may vary in a range from 0.2 to 1.6 μg/g (de Roodt et al. 2010, 2019), and an important variation in toxicity, up to three fold, was observed in the ven om from specimens of the same region (de Roodt et al., 2019). The electrophoretic profiles of the venom of T. carrilloi n. sp. showed interpopula tional differences biochemically and immunolog ically. Remarkably, the toxicity of the venom of the population of T. carrilloi n. sp. from the area of Buenos Aires city, the biggest urban area occu pied by this species, is comparably lower to those from other regions (de Roodt et al., 2010, 2014, 2019); most probably due to this it has not caused deaths yet in Buenos Aires despite the relatively high number of accidents in the area. The reason for this lower toxicity has not yet been explained, but it has to be highlighted that the population from Buenos Aires represents the southernmost extreme of distribution for this species (and the genus), and is relatively isolated from other pop ulations (Ojanguren-Affilastro et al,.2019).

Several toxins from the venom of T. carrilloi n. sp. were already isolated, like those that block K+ channels (Coronas et al., 2003; Abdel- Mottaleb et al., 2006; Saucedo et al., 2012), and toxins that modulate Na+ channels (Coronas et al., 2015). The toxicity of this venom would be related with the last type of toxin (Possani et al., 1999). The first Na+-channel toxin isolated from the venom of T. carrilloi n. sp. (originally described as for T. trivittatus), was called Tt1g (Tityus trivittatus toxin 1 gamma like), and has a 95% of homology with the gamma toxin of T. ser rulatus (Coronas et al., 2015). The κ-buthitoxin- Tt2b (κ-BUTX-Tt2b) shows structural versatility among this type of toxins (Saucedo et al., 2012), and the Tt28 was the first example of a new sub-family of toxins (a-KTx20.1), which might serve as a potential candidate for immunomod ulation studies due its action in K+ channels of T-lymphocytes (Abdel-Mottaleb et al., 2006). The TtButantoxin (TtBut-Toxin) isolated from T. carrilloi n. sp., acts on Shaker B-K+ channels and is identical to TsTX-IV from T. serrulatus (Coronas et al., 2003).

Possibly these similarities in some toxins present in the venoms of T. carrilloi n. sp. and T. serrulatus, especially regarding Na+ blockers channels toxins (Coronas et al., 2015), are re sponsible for the important experimental cross reactivity observed assaying therapeutic antiven oms of both species (de Roodt et al. 2010), and of the success observed using anti-T. serrulatus an tivenom in cases of envenomation by T. carrrilloi n. sp. (de Roodt et al,. 2003; Ministerio de Salud, 2011). However, the venoms are not identical, and consequently the antivenoms, although very useful due the paraspecific neutralization, have not the same reactivity, nor neutralizing capacity, regarding the specific antivenom (de Roodt et al., 2001, 2010). The antivenom natively produced in Argentina using venom from T. carrilloi n. sp. as immunogen, showed experimentally higher im munochemical reactivity (de Roodt et al., 2010), and neutralizing capacity, on the homologous venom regarding anti-Tityus serrulatus antiven om in neutralization experiments, showing bet ter ED50 in experiments on mice challenged with 5 LD50 of venom (de Roodt et al., 2001).

Tityus trivittatus. Scorpionism by T. trivitta tus is an emerging problem in Paraguay, which is not currently subject to mandatory reporting, as opposed to Argentina. Children from the Greater Asunción area envenomed by T. trivittatus have presented psychomotor agitation, profuse sweat ing, serum hypokalemia, and altered cardiac frequency as a result of left ventricular dysfunc tion (Borges & Rojas de Arias, 2019). These are known consequences of the exacerbation of neu rotransmitter release because of the action of low molecular mass scorpion venom neurotoxins either on voltage-sensitive sodium (NaTx) or po tassium (KTx) channels expressed in excitable tissues. Some of these manifestations have also been observed in the case of envenomation by T. carrilloi n. sp. (de Roodt et al., 2003). Lethality of T. trivittatus venom (medium lethal dose, LD50 = 1.19 mg venom/kg mice body weight) is within the same range of toxicity of other Tityus scorpion venoms in South America including T. carrilloi n. sp. and T. serrulatus (Borges et al., 2020a). Comparative mass spectrometry of T. trivittatus and T. carrilloi n. sp. venoms have revealed the existence of shared as well as spe cies-specific NaTxs, the components mainly as sociated with lethality of buthid scorpion ven oms. In the NaTx mass range (6-8 kDa), pep tides unique to T. trivittatus were components 6726.6, 6916.5, and 7263.5 Da. Whereas peptides unique to T. carrilloi n. sp. were 6630.0, 6754.5, 6787.5, 7047.9, 7324.1, and 7598.4 Da. Both spe cies shared two components in this mass range, 6606.1 and 6941.1 Da, the latter corresponding to toxin Tt1g, isolated from T. carrilloi n. sp. ven om obtained from Entre Ríos, Argentina (Borges et al., 2020a). Tt1g is a NaTx acting on the ac tivation component of voltage-gated sodium channels and specifically modifies sodium chan nel subtypes Nav1.2 and Nav1.3 (Coronas et al., 2015). No components were shared in the mass range of KTxs and antimicrobial peptides (2-5 kDa). Some degree of commonality in the phys iopathology of envenomation by both species is expected because of shared NaTxs, and also hyaluronidases and metalloproteases (Borges et al., 2020b). However, it cannot be discarded at present that differences may exist in venom function between T. trivittatus and T. carrilloi n. sp. considering that phylogenetically related NaTxs with distinct surface chemistry differ entially promote release of neurotransmitters and recognize tissue-specific voltage-gated sodi um channel subtypes (Vasconcelos et al., 2005; Borges & Graham, 2016). Species-specific prote ases in T. carrilloi n. sp. and T. trivittatus have also been uncovered by in-gel digestion and mass spectrometry procedures (Borges et al., 2020a). Additionally, the fact that no KTxs are shared be tween T. trivittatus and T. carrilloi n. sp. is also indicative of potential physiopathological differences considering that KTxs are among the most expressed toxins in venom glands of buthid scor pions and that potassium channels are the most diverse pharmacological targets of scorpion ven oms from a functional standpoint (Kuzmenkov et al., 2015).

Preliminary in vivo neutralization assays us ing anti-T. carrilloi n. sp. and anti-T. serrulatus antivenoms suggest that T. trivittatus venom is differentially recognized by these antibodies (Borges et al., 2020b). The anti-T. carrilloi n. sp. antivenom in partial experiments, using 3 LD50 of T. trivittatus venom preincubated with 100 ul of antivenom, protected half of the mice challenged (2 survivors over 4 tested) as opposed to incubation with anti-T. serrulatus antivenom (4 surviving over 4 challenged). This suggests that T. trivittatus venom is differentially recog nized by these antibodies (Borges et al., 2020b). Additionally, competitive enzyme-linked immu nosorbent assays indicated that T. trivittatus and T. carrilloi n. sp. venoms differ in their binding to Argentinean antivenom antibodies (Borges et al., 2020b). Further experiments are required to determine the true neutralization efficiency of these antivenoms in the case of T. trivittatus, and the basis for the possible immunological differ ences among T. trivittatus, T. serrulatus, and T. carrilloi n. sp. venoms. Experimental results ob tained in neutralization assays performed with therapeutic anti-scorpion antivenoms should be carefully interpreted due to the differences in pharmacological presentations of the available products (de Roodt et al., 2014). These differenc es could influence the results of the immunolog ical studies, not due to immunological reasons, but pharmacological, related with potency re quired by pharmacopeias, and protein content, among other factors. As the scorpionism prob lem in Paraguay is emerging, research is cur rently being carried out to determine the extent of the venom relationships between T. trivittatus and its synanthropic Argentinean and Brazilian congeners.

ACKNOWLEDGMENTS

FSC thanks Lita Castañeda Betancur for her help in the molecular laboratory. Part of this work was supported by a grant from CONACYT-México, Ciencia Básica project number A1-S- 15134 to FSC. AB is thankful to CONACYT-Paraguay for financial support (project PRID18- 12). DGO & AAOA are thankful to the director of the National Museum of Natural History of Paraguay Luis Moran for giving us his support. DGO is thankful to M. Sánchez, J. Movia and N. Cantero, for helping in the capture of specimens. AAOA is thankful to CONICET-Argentina for fi nancial support (projects PIP 2015-0672 & PUE 2016-0098) , to Lucas Damer who provided the type material of Tityus carrilloi n. sp., to Nadine Dupérré and Danilo Harms for their help with the photos of the type material of Tityus trivit tatus, to Abel Pérez González for his help in our collection trip to Paraguay, and particularly to Family Guerrero-Orellana for their hospitality. We are also indebted to Leonardo Carvalho, and an anonymous reviewer, as well as to the editor Luciano Patitucci for their comments on an ear lier version of the MS.

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Recibido: 04 de Febrero de 2021; Aprobado: 04 de Junio de 2021

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