TRABAJOS CIENTÍFICOS

A new species of Bryophaenocladius (Diptera: Chironomidae) from Argentina

Una nueva especie de Bryophaenocladius (Diptera: Chironomidae) de Argentina

 

Donato, Mariano

Laboratorio de Sistemática y Biología Evolutiva (LASBE). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata. Paseo del Bosque s/n, B1900FWA, La Plata, Argentina; e-mail: mdonato@fcnym.unlp.edu.ar

Recibido: 20-II-2011
Aceptado: 30-VII-2011

 

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ABSTRACT. The male of Bryophaenocladius carolinae sp. nov. is described and figured. The species can be separated from all other Neotropical species by having a hyaline, blunt triangular anal point, a comparatively small, sub-rectangular inferior volsella, gonostylus widened medially with an outer heel, R₄₊₅ ending opposite to end of M₃₊₄, setose squama and absence of comb on middle tibia and pseudospurs. A key to the adult males of the Neotropical Bryophaenocladius Thienemann is provided.

KEY WORDS. Orthocladiinae; Systematics; Neotropics; Key.

RESUMEN. Se describe y se dibuja el macho de Bryophaenocladius carolinae sp. nov. La especie puede separarse del resto de las especies Neotropicales porque posee una punta anal hialina y triangular, con su punta redondeada; la volsella inferior sub-rectangular y comparativamente más pequeña; gonostilo ensanchado en su parte media y con una quilla externa; R₄₊₅ finalizando opuesta a la terminación de M₃₊₄; escama setosa, pseudospinas y peine en la tibia de la pata dos, ausentes. Se brinda una clave de identificación de adultos machos neotropicales del género Bryophaenocladius Thienemann.

PALABRAS CLAVE. Orthocladiinae; Sistemática; Neotrópico; Clave.

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INTRODUCTION

The genus Bryophaenocladius Thienemann is distributed worldwide, with the possible exception of Australasia. The genus is very rich with more than 100 species recorded (Du et al. 2011). Most species of Bryophaenocladius appear to be terrestrial or semi-terrestrial (Cranston et al., 1989) but Strenzke (1942) recorded immatures of B. subvernalis (Edwards) from two alpine lakes.
The delimitation of this genus is difficult since there are exceptions for nearly all diagnostic characters, but in the last ten years several revisions clarify its systematics and the topic is still in progress (Wang et al., 2001; 2004; 2006; Du et al., 2011).
In this contribution, a new species of the genus Bryophaenocladius is described based on male specimens and the key to adult males of the genus for the Neotropical region by Wang et al. (2006) is updated.

MATERIAL AND METHODS

The specimens were collected with a sweep net. Microscope slides were made by clearing with 10% KOH; neutralization with glacial acetic acid; dehydration in 80%, 96% and 100% ethanol and mounting in Canada Balsam. Morphological measurements follow Sæther (1980) in μm rounded to the nearest 5 unless otherwise stated. Measurements are given as ranges followed by measurements of the holotype in square brackets.
Comparisons with other members of the genus Bryophaenocladius were made from the original descriptions and revisions. In addition, the new species was compared with the holotype of Bryophaenocladius nidorum (Edwards) housed in the Natural History Museum (London, UK) and collection material of B. aestivus (Brundin), B. cf. astis (Roback), B. flavoscutellatus (Malloch) and B. pleuralis (Malloch) deposited in the Department of Natural History, Bergen Museum, University of Bergen, Norway. The holotypes of the species described by Dr. Manabu Sasa were studied from the National Museum of Nature and Science Tokyo (Japan), Type Specimen Database (http://www.type.kahaku.go.jp/TypeDB/diptera),except B. ikiheius Sasa et Suzuki which was not found in this database.
The holotype and paratypes of Bryophaenocladius carolinae sp. nov. are housed in La Plata Museum, Argentina (MLP).

RESULTS

Bryophaenocladius carolinae sp. nov.

Diagnosis: The species can be separated from all other Neotropical species by the following combination of characters: anal point hyaline, triangular with blunt apex; inferior volsella comparatively small, sub-rectangular; gonostylus widened medially, with outer heel indicated;  R₄₊₅ ending opposite to end of M₃₊₄, squama setose and comb on middle tibia and pseudospurs absent.

Male (n = 2-3)

Total length 2.45-2.65 [2.45] mm (2). Wing length 1.34-1.58 [1.34] mm. Total length/wing  length  1.72-1.83  [1.83]  (2). Wing length/length of profemur 2.68-2.85 [2.68] (2). Coloration blackish brown.
Head. Antennae with 13 flagellomeres, AR 1.36-1.41 [1.41], ultimate flagellomere length 410-450 [410] μm. Temporal setae 10-11 [11], divided in 4 inner verticals, 3 outer verticals and 3-4 [4] postoculars. Clypeus with 8-14 [11] setae. Cibarial pump, tentorium, and stipes as in Figure 1. Tentorium 135-157 [135] μm long, 22-34 [29] μm wide. Stipes 127-135 [127] (2) long μm, 42-47 [42] μm wide (2). Palp segment lengths (in μm): 29-34 [29]; 39-49 [39]; 125-140 [125]; 108-115 [108]; 127-142 [127]. Third palpomere without finger-like apical extension, without sensilla clavata.

Figs. 1-3. Bryophaenocladius carolinae sp. nov. Male adult. 1, Tentorium, stipes and cibarial pump; 2, thorax; 3, wing.

Thorax (Fig. 2). Antepronotum with 6-8 [6] lateral setae. Dorsocentrals 25-29 [25]; acrostichals 16-17 [16] (2); prealars 8-10 [8]. Scutellum with 11-14 [11] setae.
Wing (Fig. 3). Microtrichia visible at 100x magnification. R₄₊₅ ending opposite to end of M₃₊₄. VR 1.26-1.29 [1.28]. C extension 32-66 [32] μm. Brachiolum with 1-2 [2] setae; R with 11-13 [11]; R₁ with 6-11 [6]; R₄₊₅ with 0-3 [3]. Squama with 6-9 [6] setae.
Legs. Spur of front tibia 64-76 [64] μm long; spurs of middle tibia: 22-27 [22] μm and 47-54 [47] μm; of hind tibia: 22-32 [22] μm and 51-69 [51] μm long. Width at apex of front tibia 32-39 [32] μm; of middle tibia 27-42 [34 ]μm; of hind tibia 44 μm. Middle tibia without comb. Comb of hind tibia with 11-12 [11] setae, longest 37-44 [37] μm long, shortest 20-27 [20] μm long. Lengths (in μm) and proportions of legs in Table I.

Table I. Lengths (in μm) and proportions of legs of Bryophaenocladius carolinae n. sp. (male) (n = 2-3). Abbreviations: Femur (Fe); Tibia (Ti); Tarsomeres 1-5 (Ta_1-5); Leg Ratio (LR), ratio of metatarsus to tibia; Beinverhältnisse» (BV), combined length of femur, tibia, and basitarsus divided by combined length of tarsomeres 2-5; «Schenkel-Scheine-verhältnis» (SV), ratio of femur plus tibia to metatarsus.

Hypopygium (Figs. 4-7). Anal point hyaline, bluntly triangular, 27-31 [31] μm long, 39-42 [39] μm wide at base; anal point length/width 1.26-1.52 [1.26]. Tergum IX with 8-12 [8] setae, laterosternite IX with 6 setae. Phallapodeme 49-61 [51] μm long; transverse sternapodeme 110-130 [110] μm long. Virga 22-27 [25] μm long, with two spines. Gonocoxite 194-206 [194] μm long, inferior volsella sub-rectangular with a dorsal lobe with 5-6 [5] apical setae and a ventral lobe with 2-3 [2] apical setae (Figs. 6-7); ending 95-115 [100] from apex of gonocoxite; distance from apex of gonocoxite to apex of inferior volsella 110-122 [110]; ratio of "inferior volsella ending from apex of gonocoxite/length of gonocoxite" 0.47-0.56 [0.52]. Gonostylus 96-105 [96] long, widest medially and with a slight angulate subapical heel; crista dorsalis absent; megaseta 10-12 [10] long (9). HR 1.93-2.1 [2.02]; HV 2.55- 2.7 [2.55] (2).

Figs. 4-7. Bryophaenocladius carolinae sp. nov. Male adult. 4, Hypopygium dorsal view; 5, hypopygium with tergite IX removed, right ventral view, left dorsal view; 6, inferior volsella dorsal view; 7, inferior volsella ventral view.

Etymology. Dedicated to my wife Carolina, for her patience and support.

Type material. ARGENTINA. Buenos Aires: Holotype male, MLP number 5312/1: Los Hornos, 34º 57' 32''S- 58º 00' 57''W, 16-IV-2005, sweep net, M. Donato leg. (MLP). Paratypes, MLP numbers 5312/3-4: 2 males, same data as the holotype.

DISCUSSION

The genus Bryophaenocladius is one of the largest genera in the subfamily Orthocladiinae. The systematics and taxonomy of this genus is based mainly on males with a few exceptions that are based on females and  the knowledge of its immature stages is scarce. The variation in the taxonomic characters is large, mainly in the shape  of  the hypopygium. Wang et al (2006) pointed out that the species defined as belonging to Bryophaenocladius are based on a combination of characters and they also considered that probably this character variation could give rise to split the genus into several genera or subgenera in the future when the revision of the genus is completed.
The  new  species  here described was established  after  a  comparison  with  the rest of the species of the genus from their original descriptions or from a revision, as well as after the study of their holotypes or collection material. In this way, 92 species of the genus   Bryophaenocladius were compared with B. carolinae and studied in order to account for the variation in the taxonomic characters pointed out by Wang et al. (2006). The  taxonomic characters were divided into two groups based on their importance in delimiting species. As a result, the most important characters used to  define  the  Bryophaenocladius  species are the shape of the anal point, the shape of inferior volsella, presence or absence of virga, shape of gonostylus, the presence and  different  degree  of  development  of the crista dorsalis, presence or absence of the finger-like projection on palpomere 3 and wing punctuation. Other characters used in the species diagnosis,  although less important, are the presence or absence of wing anal lobe, number of setae on R₁ vein, different degree of development of acrostichal setae, length of Costal extension, length of megaseta, presence or absence of pseudospurs, presence or absence of a comb at apex of middle tibia, presence or absence of oral projections in sternapodeme, number of palpomeres and AR. Among the characters mentioned above as the most important, the character shape of anal point was found as a very good character since it has six well defined character states and only two particular character states. The character states found for this character are anal point long with rounded apex [e.g. B. aestivus (Brundin)]; anal point pointed triangular [e.g. B. flexidens (Brundin)]; anal point wide, trapezoidal [e.g. B. inconstans (Brundin)]; anal point bluntly triangular [e.g. B. scanicus (Brundin)]; anal point sharply triangular (e.g. B. parinberbus Wang et Du) and anal point subtriangular (e.g. B. usambarensis Andersen et Schnell). The other character states found were anal point small triangular (present in B. togatenuis Sasa et Okazawa) and anal point absent (present in B. ikiheius Sasa et Suzuki).
The combination of characters anal point bluntly triangular and hyaline, gonostylus widened medially, virga present and finger-like apical extension on palpomere 3 present in Bryophaenocladius carolinae are shared with three species of the 92 species studied of the genus. The species B. digitatus Sæther is clearly distinguished from B. carolinae by the presence of a weak comb at apex of middle tibia, wing punctuation coarse and inferior volsella digitate with few curved setae dorsally. The species B. kobayashii Makarchenko et Makarchenko differs from B. carolinae by the presence of a rounded inferior volsella. The species B. xinglongensis Du et Wang is clearly distinguished from the new species here described by the presence of a not obvious and setose inferior volsella and R₄₊₅ ending distal to end of M ₃₊₄.

                                   

Key to males of the genus Bryophaenocladius from the Neotropical region (modified from Wang et al. 2006)

1. Palp with 4 short palpomeres .................................................  Bryophaenocladius carus (Roback). Panama, Brazil - Palp with 5 well-developed palpomeres ... 2

2. Third palpomere with digitiform projection   ........................................................................... Bryophaenocladius simplex Wang, Andersen et Sæther. Mexico - Third palpomere without projection .....................................................................  3

3.  Inferior volsella digitiform; mid leg with weak comb   .......................... Bryophaenocladius digitatus Sæther. Mexico -  Inferior volsella rounded or sub-rectangular  .............................................   4

4.  Pseudospurs absent ...... Bryophaeno-cladius carolinae sp. nov. Argentina -  Pseudospurs present ........................ 5

5. Megaseta simple; transverse sternapodeme lacking oral projections  ...................... Bryophaenocladius humerosus Wang, Andersen et Sæther. Mexico -  Megaseta with several teeth; transverse sternapodeme with pronounced oral projections ...........................................................  Bryophaenocladius pichinensis Wang, Andersen et Sæther. Mexico

ACKNOWLEDGEMENTS

I greatly acknowledge Trond Andersen and Humberto Mendes for their hospitality, kindness and help during my visit to Bergen. In addition, I wish to thank Trond Andersen for his comments and suggestions on this work and his advice to improve my drawings. Also thanks to two anonymous reviewers for their comments and suggestions that have improved this paper. Special thanks to Dr. Gustavo R. Spinelli, specialist of Ceratopogonidae of the Museo de La Plata, who examined the type of B. nidorum at the Natural History Museum in London.This paper was supported by grant PIP N° 0729 (CONICET).

LITERATURE CITED

1. CRANSTON, P. S., D. R. OLIVER & O. A. SÆTHER. 1989. The adult males of Orthocladiinae (Diptera: Chironomidae) of the Holarctic region - keys and diagnoses. Entomologica Scandinavica Supplement 34: 165-352.         [ Links ]

2. DU, J., X. H. WANG & O. A. SÆTHER. 2011. Redescriptions of species of Bryophaenocladius Thienemann, 1934 (Diptera: Chironomidae) described by Brundin (1947). Zootaxa 2743: 40-48.         [ Links ]

3. SÆTHER, O. A. 1980. Glossary of chironomid morphology terminology (Diptera: Chironomidae). Entomologica Scandinavica Supplement 14: 1-51.         [ Links ]

4. STRENZKE, K. 1942. Terrestrische Chironomiden XII: Bryophaenocladius subvernalis Edw. (Chironomiden aus dem Lunzer Seengebiet IV). Zoologischer Anzeiger 137: 177-185.         [ Links ]

5. WANG, X. H., O. A. SÆTHER & T. ANDERSEN. 2001. Afrotropical Bryophaenocladius Thienemann, 1934 (Diptera, Chironomidae). Studia Dipterologica 8: 447-462.         [ Links ]

6. WANG, X. H., T. ANDERSEN & O. A. SÆTHER. 2006. Neotropical Bryophaenocladius Thienemann, 1934 (Diptera: Chironomidae). Studies on Neotropical Fauna and Environment 41: 19-32.         [ Links ]

7. WANG, X. H., Z. LIU & J. H. EPLER. 2004. New species of Bryophaenocladius Thienemann from the Nearctic Region (Diptera: Chironomidae: Orthocladiinae). Zootaxa 581: 1-10.         [ Links ]