Eucypris fontana(Graf, 1931) (Crustacea, Ostracoda) in permanent environments of Patagonia Argentina: a geometric morphometric approach

Abstract

-Ostracods are microcrustaceans with a calcareous carapace, very useful as paleoenvironmental indicators. Eucypris fontana (Graf, 1931) is a non-marine ostracod species, distributed in southern Neotropics, commonly found in living bisexual populations as well as in quaternary sequences in Patagonia. Geometry morphometric analysis offers efficient and powerful techniques to quantify, describe and analyze shape and size variations. In this study, phenotypic changes in the carapace (size and shape) of E. fontana were analyzed using geometric morphometric methods. One hundred and two valves, including males and females from surface sediments of six permanent water bodies located in Patagonia, Argentina, were analyzed. Male and female valves are spread in the morphospace and sexual dimorphism in size and shape were no perceived. Valve size (centroid size) differed between environments; larger individual were correlated with higher Mg 2+ , Ca 2+ , K + concentrations and temperature and lower pH ( y 9.1) of the host waters, whereas smaller specimens were associated with the opposite environmental extreme. The principal component analysis performed with Procrustes coordinates (shape) indicated a morphological gradient between elongated and rounded valves; major changes occurring on the dorsal margin, calcified inner lamella and in the position of the adductor muscles scars. Rounded carapaces were related whit higher Ca 2+ and Mg 2+ concentration and lower pH ( y 8.6) environments, whereas elongated valves were associated with the opposite environmental extreme. These results highlight the importance of morphometric studies of E. fontana in ecological research and their potential use in paleoenvironmental studies in Patagonia and other regions where this taxon is found.

Changes in ostracod assemblages and morphologies during lake‐level variations of Lago Cardiel (49°S), Patagonia, Argentina, over the last 15.6 ka

“…To date, the elongated morphotype has been found in surface sediment from lakes characterized by waters with conductivities within the oligohaline to mesohaline range (1234 to 6153 μS cm −1 ) and lower Ca 2+ (0.5 to 0.9 mEq L −1 ) and Mg 2+ (0.2 to 1.8 mEq L −1 ) concentrations and higher pH (~9.1) than the rounder morphotype (Ca 2+ = 0.7 to 3.1 mEq L −1 ; Mg 2+ = 4.2 to 11.0 mEq L −1 ; pH ~8.6) (Ramos et al . ). Morphological changes during the Early Holocene, i.e.…”

“…; Ramos et al . ). Genetic characteristics of initial founder populations, ecological conditions and geographical isolation may play significant roles in the determination of the morphological characteristics of ostracod populations (Iepure et al .…”

“…Individuals of L. rionegroensis and R. whatleyi were selected and analysed using a morphometric approach in order to compare these results with previous studies reporting the intraspecific morphological variability of the same species from modern populations (Ramos et al . , ). To accomplish this comparison, we used the morphological data set (ornamentation, size and shape variations) of R. whatleyi and L. rionegroensis from modern Patagonian lakes presented in Ramos et al .…”

“…To accomplish this comparison, we used the morphological data set (ornamentation, size and shape variations) of R. whatleyi and L. rionegroensis from modern Patagonian lakes presented in Ramos et al . (, ) and therefore, the same morphometric methods applied previously to these species were employed. Concerning the fossil data set, all well‐preserved valves from core CAR 99‐7P were chosen for morphometric analysis because this core contains a greater abundance of ostracods over a longer period of time than core CAR 99‐9P.…”

“…Furthermore, the morphological variability between populations of two widely distributed species, Eucypris fontana (Graf, 1931) and Limnocythere rionegroensis Cusminsky & Whatley, , was determined, allowing further exploration of the relationship between morphological patterns and ecological variables (Ramos et al . , ). Morphological intraspecific variations in ostracod valves are the result of complex interactions between genotype and environment (Baltanás & Geiger ).…”