Foregut anatomy and predation by Charonia lampas (Gastropoda: Prosobranchia: Neotaenioglossa) attacking Ophidiaster ophidianus (Asteroidea: Ophidiasteridae) in the Açores, with a review of triton feeding behaviour

Abstract

This paper is the first to describe, in detail, the process of feeding by a species of Charonia. As Charonia lampas commenced attacking its sea star prey, Ophidiaster ophidianus, the latter autotomized its trailing arm and escaped. The pursuing C. lampas ate this arm. The results of this study are not in accord with the established view of feeding by species of Charonia. Firstly, C. lampas did not inject either a venom into its prey to paralyse it nor an acid to access it and, second, nor did it pierce the skeleton of its prey and suck out the tissues, all as reported in the literature. Rather, in the case herein described, C. lampas held and manipulated its prey with the foot and used its taenioglossan radula located at the end of the extendible pleurembolic proboscis to scrape and ingest the soft tissues of the sea star and, subsequently, consume the remaining skeletal components again using the proboscis and contained radula. These two phases of consumption were followed by two matching phases of faeces production. Also described is the foregut anatomy of C. lampas, including, for the first time, the minute jaws and the histology of the salivary glands, and for which comparison is made with those of the known acid-producing structures of representatives of the Cassidae and other Ranellidae. As finally described, predator and prey clearly recognised each other signifying an identifiably intimate relationship. Charonia lampas consumed only the autotomised arm and it is argued that in such a case, as an anti-predation device, autotomy is of survival benefit to both predator and prey.

Keywords:

• Charonia lampas
• Ophidiaster ophidianus
• triton
• asteroid
• predation
• radula
• jaws
• salivary glands
• co-evolution

Acknowledgements

I am grateful to Prof A. M de Frias Martins and Dr Joana Xavier for hosting this research trip and to the team of divers, especially Dr Joana Micael (all University of the Açores), for collecting the animals herein reported upon and for the benefit of useful discussions. I am also grateful to Dr Rafael Araujo, Museo Nacional de Ciencias Naturales (CSIC), Madrid, Spain, for the loan of a specimen of Charania lampas and for permission to dissect it. Thanks also to Sanja Puljas (University of Split, Croatia) for histological assistance. Finally I would like to thank colleagues Dr Alan Beu (Institute of Geological and Nuclear Science, New Zealand), Dr John Taylor (The Natural History Museum, London) and Dr Nathalie Yonow (Swansea University) for critical comments on the manuscript of this paper and pointing me towards references I would not otherwise have detected.