Comportamento alimentar de nudibrânquios no litoral do Rio de Janeiro (Gastropoda, Nudibranchia, Doridacea)

• Autor(a) principal: Belmonte, Thalita Dionisio
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/13887
• topic: Chemical interaction; Diet; Mollusca; Porifera; Predation; Interação química; Dieta; Mollusca; Porifera; Predação; CNPQ::CIENCIAS EXATAS E DA TERRA::OCEANOGRAFIA::OCEANOGRAFIA BIOLOGICA

Nudibranch gastropods are carnivores and many species have very specialized diets, preying on a single or a few species of marine sponges. Up to date, there is no specific study on the ecology of Brazilian nudibranch species addressing any interaction with other groups of marine animals. There are also no studies on biological assays to evaluate the feeding behavior and chemical mediation between nudibranchs and their preys. The objectives of this research were: a) to record in situ predation of dorid nudibranchs in Rio de Janeiro State, through identification of the species involved and compare to patterns of predation observed in other regions, and b) to evaluate the behavior of chemical attraction of nudibranchs in relation to their preys. Observations on the diet of dorid nudibranchs were made by free or SCUBA diving and their behavior in relation to the sponges were record. A total of 139 observations were made on 15 dorid nudibranchs species: Felimida binza; Felimida paulomarcioi; Felimare lajensis; Tyrinna evelinae; Cadlina rumia; Diaulula greeleyi; Discodoris evelinae; Geitodoris pusae; Jorunna spazzola; Jorunna spongiosa; Rostanga byga; Taringa telopia; Doris kyolis; Dendrodoris krebsii and Tayuva hummelincki. The predation was confirmed for 89 (64%) out of 139 observations and 12 (80%) out of 15 dorid nudibranch species. Predation is the main ecological interaction between dorids and sponges in Rio de Janeiro. In laboratory conditions, the feeding behavior of Cadlina rumia and Tyrinna evelinae were evaluated in double choice preference assay being offered fresh sponges. Assays of fresh sponges, powder of lyophilized sponges and crude extract of sponges were made to investigate whether the nudibranch perception to their preys is modulated by chemical signs. Cadlina rumia has not consumed any offered sponges, although detected the chemical signals of fresh sponges. Cadlina rumia has not detected the chemical signal from lyophilized sponges incorporated into artificial foods. Tyrinna evelinae detected the chemical signal from the sponge Dysidea etheria offered in two different ways: fresh and lyophilized. The in situ predation of T. evelinae on D. etheria was confirmed through laboratory assays. Our results are the first direct observations of in situ and in vitro feeding activity by any species of Tyrinna. In general, the results of field observations corroborated the feeding patterns observed in other regions. Demosponges are a very important source of food for Brazilian dorid nudibranchs. Chemical signaling and the positive taxis was evident for the nudibranch that has more specialized diet, Tyrinna evelinae, and not for one who feeds on various sponges, Cadlina rumia.