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Diet, prey selection and cannibalism in the hunter opisthobranch Roboastra europaea

Published online by Cambridge University Press:  09 April 2003

César Megina
Affiliation:
Departamento de Biología, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz. Apartado 40, 11510-Puerto Real, Cádiz-Spain
Juan Lucas Cervera
Affiliation:
Departamento de Biología, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz. Apartado 40, 11510-Puerto Real, Cádiz-Spain
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Abstract

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The diet and predatory behaviour of the nudibranch Roboastra europaea (Mollusca) is described and compared with other nudibranch-hunting opisthobranchs. The natural diet in the Strait of Gibraltar was studied by the analysis of gut contents. Roboastra europaea is a specialist predator of nudibranchs, and the diet is comprised essentially of the polycerids Polycera sp., Polycerella emertoni, Limacia clavigera and conspecific R. europaea. One or several Polycera species appeared as the most dominant prey.  The complete assemblage of potential prey of this predator—the fundamental diet—was assessed in laboratory trials that included all likely prey groups. This predator consistently rejected both non-nudibranch species and non-polycerid nudibranchs. Roboastra europaea is exclusively a predator of polycerids and previously unencountered polycerids are also potential prey items.  As most of the hunter opisthobranchs, R. europaea exhibited cannibalistic behaviour, to the extent that aggressiveness prevailed over mating in intraspecific encounters. Roboastra europaea as prey showed a complex result in laboratory trials: (a) if one individual was small enough complete ingestion proceeded; (b) if there was not enough difference in size, a cannibal attack proceeded, but if ingestion was not possible, it could result in mating behaviour.

Type
Research Article
Copyright
2003 Marine Biological Association of the United Kingdom