Heterocypris (Crustacea, Ostracoda) from the Isole Pelagie (Sicily, Italy): The coexistence of different morphotypes

Abstract

Differences exist in the population structure of Heterocypris in five temporary ponds on the islands of Lampedusa and Linosa (Isole Pelagie, south of Sicily). In a temporary pond on Lampedusa (Cavallo Bianco) we found only H. incongruens females. All the other populations were bisexual, with the female/male sex ratio varying from 1 to 18. We analysed and measured a sub-sample from each population and observed, as a typical morphological feature of adult females in the bisexual populations, a lobe-like expansion of the selvage (lamella hyalina) on the posterior margin of the left valve. In another temporary pond from Lampedusa (Vallone della Forbice) both females with this lamella and others without it occur. We discuss the possible coexistence of two lineages of H. incongruens each having a different reproductive mode. The parthenogenetic lineage comprises females without a lamella hyalina whereas the bisexual females possess this feature. Alternatively, we hypothesise the sympatry of two different species of Heterocypris: H. incongruens and H. barbara. In this hypothesis, H. incongruens is parthenogenetic and H. barbara is amphimictic. Differences in mean body size between the adult females with and without the lamella hyalina are in accordance with values reported in the literature for niche differentiation among sympatric taxa.

Experimental assessment of the fecundity of Eucypris virens (Ostracoda, Crustacea) under natural sex ratios

“…, 2004), using factorial combinations of temperatures and photoperiods, sex ratios of H. incongruens hatchlings either did not differ significantly from 1 : 1 (108 males for 124 sexual females) or were male biased (41 males for 20 sexual females). Also in both these cases the sex ratios in the source populations were biased towards females (1 : 1.1 to 1 : 17.8; Bellavere et al. , 2002).…”

“…Recent and fossil sex ratios are usually female biased, often within the range of one male for every one to four females (reviewed by Chaplin, Havel & Hebert, 1994). This bias is found in a variety of non‐marine systems, including deep lakes (Chaplin, 1993), coastal marshes (Mezquita, Olmos & Oltra, 2000), streams (Havel, Hebert & Delorme, 1990) and temporary pools (Bellavere et al. , 2002).…”

“…A broad spectrum of explanatory mechanisms could account for the reported patterns of sex ratio variations within and among natural populations of ostracods, of which sex‐specific phenologies and contamination with asexual lineages are thought to be the most important (McKenzie, 1971; Bellavere et al. , 2002).…”

Insights into biodiversity sampling strategies for freshwater microinvertebrate faunas through bioblitz campaigns and DNA barcoding

“…Ostracods are very common in benthic freshwater communities, but also occur in marine, intertidal, or semi-terrestrial environments. They are useful model organisms for studies on various aspects of ecology and evolution [1-5], given the high prevalence of their calcified bivalve shells in the freshwater fossil record as well as their variability in breeding systems [6,7]. In freshwater systems alone, the class Ostracoda has been conservatively estimated to number close to 2,000 described species [8], with 420 freshwater species recorded for North America [9,10].…”

Morphological differentiation of seven species of the genus Heterocypris Claus, 1892 (Ostracoda, Crustacea) based on the upper lip

“…This genus has a cosmopolitan distribution and comprises 63 species worldwide (Martens & Savatenalinton 2011). The presence of both parthenogenetic and amphimictic populations in many Heterocypris species, with possible intra-and interspecific hybridization, has resulted in high genetic and morphological variability (Turgeon & Herbert 1994, Bellavere et al 2002, Martens et al 2002, Rossi et al 2007. The taxonomy of this genus is based mostly on carapace characteristics, while distinctive features of appendages is owed to Dr Trajan Petkovski for contribution of many samples.…”