Taxonomic revision of Cypridopsis silvestrii comb. nov. (Ostracoda, Crustacea) from Patagonia, Argentina with morphometric analysis of their intraspecific shape variability and sexual dimorphism.

In this study we redescribe an ostracod species belonging to the subfamily Cypridopsinae Kaufmann, 1900, sampled in seven localities of northern and southern Patagonia, Argentina. A new taxonomical combination is proposed, Cypridopsis silvestrii comb. nov., based on detailed description of females and the first descriptions of males. Cypridopsis silvestrii occurred on a wide geographical distribution range, from 40º to 48º S latitude, as well as broad environmental tolerance ranges. We evaluated morphological variations in two populations of C. silvestrii from northern (El Toro lake) and southern (El Sello lake) Patagonia, with contrasting limnological conditions. El Toro is a small shallow lake with high salinity waters and El Sello is a large deep lake with lower salinity. Based on morphometric analysis, our results showed intraspecific variation in valve shape and size between populations. Sexual dimorphism in El Toro population was identified through morphometric analyses. Additionally, comparison of valve outlines in living and subfossil individuals from El Toro lake allowed specimens previously described as juveniles of Eucypris fontana (Graf, 1931) to be identified as adults of C. silvestrii comb. nov. The present contribution increases knowledge of the taxonomic identity, the ecological requirements and the geographical distribution of C. silvestrii, and shows that morphometric analyses are a feasible and useful tool for exploring intraspecific shape differences and assisting in taxonomic identification. Furthermore, the results presented herein provide tools for C. silvestrii identification in paleolimnological studies, and emphasize the usefulness of studying living representatives for clarification of the taxonomic status of species widely distributed in Quaternary sediments.

Mycosporine-like amino acids in freshwater copepods: potential sources and some factors that affect their bioaccumulation.

Mycosporine-like amino acids (MAAs) are ubiquitous photoprotective compounds in aquatic environments. MAAs are synthesized by a wide variety of organisms (i.e. bacteria, fungi and algae) and their production is photoinducible by ultraviolet radiation (UVR) (280-400 nm) and/or photosynthetically active radiation (400-750 nm). Most animals however, are unable to synthesize MAAs and must acquire these compounds through their diet or from symbiotic organisms. In this paper, we investigate the possible sources of MAAs and factors (temperature and initial MAA concentration) that may affect their bioaccumulation in freshwater copepods. We found that MAA accumulation may occur even if the copepods are cultured on a MAA-free diet. In addition, we found that the bacteriostatic antibiotic, chloramphenicol, inhibits the bioaccumulation of MAAs. These two pieces of evidence suggest that the source of MAAs in these copepods may be prokaryotic organisms in close association with the animals. The two factors investigated in this study, temperature and initial MAA concentrations, were found to affect the rates at which MAAs are accumulated. Temperature had positive effects on both uptake and elimination rates. On the other hand, the rate of uptake decreased at the highest assayed initial MAA concentration, probably because the concentration of MAAs was already close to saturation.