Heterocypris(Crustacea, Ostracoda) from the Isole Pelagie (Sicily, Italy): Population genetics

Abstract

We analysed the genetic structure of five populations of Heterocypris from small temporary ponds on the islands of Lampedusa and Linosa (Isole Pelagie, South of Sicily) where we have observed two different adult females morphotypes. The most genetically-differentiated population, Cavallo Bianco, is made up by females only showing a morphology typical of H. incongruens. All other populations, from both islands, are bisexual and their adult females present a lobe-like expansion of the selvage (lamella hyalina) on the posterior margin of the left valve. In one locality, Vallone della Forbice, both female morphotypes occur. The analyses of individuals raised in the laboratory microcosms confirmed the genetic differentiation between morphotypes and their different reproductive modes. The adult females without a lamella hyalina are apomictic, whereas females with this feature are amphimictic. Genetic differentiation of the two female morphotypes is compatible with the hypothesis that the two morphotypes represent different species of Heterocypris although, such a morphological differentiation is not unusual in populations of the same parthenogenetic species, and we found evidence of hybridisation between males and parthenogenetic females.

Hatching phenology and voltinism of Heterocypris barbara (Crustacea: Ostracoda) from Lampedusa (Sicily, Italy)

“…The number of juveniles, adult males, adult females and ovigerous females were recorded. By previous laboratory observations we knew that at 24°C and 12:12 L:D, H. barbara eggs hatch within 13 days and 156 DD after the microcosm filling (Rossi et al, 2003(Rossi et al, , 2004. Moreover, males and ovigerous females were distinguishable by the observation trough the transparent carapace of long sperm ducts or of eggs in the ovary.…”

“…Ignoring any potential costs of remaining dormant, if habitat quality could be predicted, the best strategy would be to hatch only when hydroperiod is favourable for recruitment. We know that a proportion of resting eggs of H. barbara from egg bank does not hatch after a first inundation event and displays a log-term dormancy (Rossi et al, 2004). The production of both resting and non resting eggs as well as delayed recruitment from them, might be seen as part of a diversified bet-hedging strategy to spread the risk of extinction and to bet on advantage of any extra time available for reproduction (Hairston et al, 1995(Hairston et al, , 1996Simovich and Hathaway, 1997;Rossi et al, 2012).…”

“…It hosts an amphimictic population of H. barbara (Rossi et al, 2007). In order to evaluate how conductivity, temperature and photoperiod affect the termination of dormancy, the life cycle and the dynamics of natural amphimictic populations of H. barbara, laboratory microcosms were set up by hydrating sediments from Aria Rossa with 500 ml distilled water in transparent cylindrical uncovered PET containers (8 cm diameter, 18 cm height) (Rossi et al, 2004). In microcosms free mating may occur at the appropriate instar.…”

“…On Lampedusa island (Isole Pelagie, Sicily channel, Italy), both amphimictic and parthenogenetic females of H. barbara were described and both forms coexist in at least one temporary freshwater pond (Rossi et al, 2003(Rossi et al, , 2004(Rossi et al, , 2007. The Mediterranean area has a predictable dry summer, but the rainfall pattern and hence the onset and duration of the wet winter season is highly variable from year to year.…”

“…The presence and persistence of H. barbara in these pools has a finite, though variable, length of time in which organisms emerge from resting eggs, grow, reproduce and return to resting stage. We have described the role of temperature, oxygen concentration, pH and conductivity in hatching phenology of resting eggs (Rossi et al, 2004). Hypoxia and high conductivity delayed or prevented hatching and resting egg may remain dormant until the following inundation (Rossi et al, 2004(Rossi et al, , 2012.…”