Ostracoda and Amphibia in temporary ponds: who is the prey? Unexpected trophic relation in a mediterranean freshwater habitat

Abstract

Small and temporary freshwater ecosystems are important biodiversity ''hot spots'' of the Mediterranean region, and their food webs are considered as very complex systems. Amphibians and ostracods are two highly ubiquitous classes of metazoans adapted to live in temporary ponds. Their trophic interactions are considered unidirectional, the amphibians acting as predators and the ostracods as preys. In the field, we observed the opposite interaction in few ponds in Northern Italy. To confirm this qualitative evidence, we set up laboratory experiments to investigate the predation by the Ostracod mussel shrimp (Heterocypris incongruens) on eggs and tadpoles of Common toad (Bufo bufo) and Stripless tree frog (Hyla meridionalis). Amphibian eggs of both species were offered to ostracods either as unique trophic resource or, alternatively, together with another kind of food. Similarly, tadpoles of both species were simultaneously offered to ostracods (with alternative food) to disclose their preferences. Ostracods preyed mainly on amphibian eggs and no significant differences in the rate of predation between toad and treefrog eggs were detected. However, ostracods preferred Bufo when offered along with Hyla tadpoles. Toad eggs and larvae are commonly considered highly unpalatable, but our results contrasted this view. The difference in the predation rate between the two tadpole species is discussed in the light of their swimming behaviour. We show that feeding relationships between Amphibia and Ostracoda are much more complex than expected and depend on both the ecological context and amphibian life stage. The knowledge of the trophic connections among taxa is a fundamental prerequisite to further and more exhaustive studies on community ecology.

Suppression of Artemia spp. (Crustacea, Anostraca) populations by predators in the Crimean hypersaline lakes: A review of the evidence

“…For example, in salt lakes in Siberia, G. lacustris G. O. Sars, 1863—a species close to G. aequicauda —intensively consumes zooplankton decreasing copepod abundance (Yemelyanova, Temerova, & Degermendzhy, ). Some other ostracod species are also characterized by the ability to provide predatory nutrition (Campbell, ; Ottonello & Romano, ; Wilkinson, Wilby, Williams, Siveter, & Vannier, ).…”

Colonization, population dynamics, predatory behaviour and cannibalism in Heterocypris incongruens (Crustacea: Ostracoda)

“…Cypridopsis hartwigi, C. vidua and Cypretta kawatai have been described as efficient predators of young Biomphalaria glabrata, the vector of schistosomiasis (Deschiens et al 1953;Deschiens 1954;Sohn & Kornicker 1972). Heterocypris incongruens preys on small organisms as Daphnia magna, Copepods, other Ostracods, Oligochaeta, Cladocera and insect larvae (Ganning 1971;Meisch 2000) and can be an active predator on amphibians (Ottonello & Romano 2010). Scavengers are able to ingest massive quantities of dead or live particles that are collected using appendages shaped by selection (McLay 1978a;Meisch 2000;Wilkinson et al 2007).…”

A review of rice field ostracods (Crustacea) with a checklist of species

“…Most free-living freshwater ostracods consume mainly algae, cyanobacteria and organic detritus, but have also been reported to feed on bacteria, fungi, protozoans, plants and pollen, fallen leaves, rotifers, oligochaetes, nematodes, copepods, cladocerans, chironomids, mosquito larvae, gastropod larvae, amphibian eggs, fish fry, assorted dead animals and even other ostracods, including individuals of the same species (Liperovskaya, 1948;De Deckker, 1983;Strayer, 1985;Campbell, 1995;Fryer, 1997;Smith and Delorme, 2010;Gray et al, 2010;Ottonello and Romano, 2011;Rossi et al, 2011). Ostracods are not widely reported to directly feed on rice plants, but in experiments, ostracods have been documented damaging the roots of two-week old rice seedlings suspended in water (Barrion and Litsinger, 1984).…”

“…Ostracods have been reported to prey on amphibian eggs and tadpoles, which most animals find unpalatable (Gray et al, 2010;Ottonello and Romano, 2011). This could potentially be another way ostracods affect the rice field environment, as amphibians act as biological controls on rice pests (Khatiwada et al, 2016).…”