From water into soil: trophic ecology of a caecilian amphibian (Genus Ichthyophis)

Tropical ecosystems have a great organismal diversity. However, the trophic relations of many components are poorly understood and this is particularly the case for caecilian amphibians. We analysed spatial and temporal aspects of the diet of a caecilian (Ichthyophis cf. kohtaoensis) at a field site in North-eastern Thailand (Mekong valley, Khemmarat District, Ubon Ratchathani Province). This is the first study to include both aquatic larvae and terrestrial adult stages of any caecilian. Larval I. cf. kohtaoensis feed exclusively on aquatic invertebrates (e.g., dragonfly larvae, water beetles and clam shrimps). A comparison of potential prey taxa available indicates that larval I. cf. kohtaoensis prefer benthic prey. Terrestrial I. cf. kohtaoensis consume mostly soil invertebrates such as megascolecid earthworms, ants and termites (soil ecosystem engineers). Numerically and in terms of their frequency of occurrence, these major prey groups varied strongly between seasons. Scarabaeid beetle larvae, oribatid and mesostigmatid mites and occasionally microhylid frogs were also recorded in the diet. During ontogeny, I. cf. kohtaoensis move from an aquatic to terrestrial existence. Despite this, accompanying changes in trophic position are superficial because both stages are carnivorous generalists. In this regard, they are more similar to salamanders than frogs with biphasic life history cycles.