Resumen

SEMENAS, Liliana  y  BRUGNI, Norma. Population characteristics and life cycle of Diplodon chilensis (d'Orbigny, 1835) (Hyriidae, Bivalvia) in Gutiérrez lake (Patagonia, Argentina). Ecol. austral [online]. 2002, vol.12, n.1, pp.29-40. ISSN 1667-782X.

Diplodon chilensis (Hyriidae, Bivalvia) is one of the most common members of the Patagonian fauna of freshwater invertebrates. It is characterized by separate sexes, marsupium in the internal hemibranchs, and glochidium as a larval stage, which parasitizes fishes. The aim of this study is to evaluate the life cycle and environmental and population parameters of this species in lake Gutiérrez, an oligotrophic lake of the Andean Patagonia, in order to amplify the knowledge about this bivalve. Sampling of Diplodon chilensis took place from April 1993 to April 1995 at a depth of 10 m and 15 m; sampling of the fish Galaxias maculatus was carried out from March 1994 to April 1995 at a depth of 0 m to 40 m. All the individuals were kept alive until processing. Weight, length and width of valve, sex, abundance of spermatozoids and number of ingravid and gravid females were recorded in Diplodon chilensis; length, presence of infected fish and number and location of glochidia were recorded in Galaxias maculatus. Length-weight relationship in Diplodon chilensis fitted a potential model, the distribution of sexes showed a 1:1 relationship, and weight and width of valves did not have differences between sexes. Differences in the size frequency distribution at 10 m and 15 m could not be attributed to any of the studied factors. The presence of maturity stages in both sexes along the year was different; hatching happened during the spring-summer months with the highest percentages of grade 3 females generally in December. There was a clear relationship among maturity of males, presence of grade 3 females and the increase of water temperature. Glochidiosis in Galaxias maculatus was not related with the increment of length; infection was between spring and autumn, and the maximum values of infection and grade 3 female percentages were in summer.

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