Invertebrate predation on egg masses of the European cuttlefish, Sepia officinalis: an experimental approach

Abstract

Sepia officinalis embryos develop inside ink-stained black encapsulated eggs fixed to the seafloor in shallow water habitats. The enveloping layers of these eggs allow the embryo to develop within a micro-environment and are thought to provide protection. Since embryological development may last months, this short-lived species spends a relatively long period of its lifespan on shallow waters, vulnerable to predation and physical stress. Yet, only a handful of species are known to feed on S. officinalis eggs, most of them fish. Marine benthic invertebrates, however, are likely candidates contributing to predation of this critical life stage. In this study, several invertebrate marine species, from 6 different phyla and with diverse feeding habits, were investigated as potential predators of S. officinalis eggs under laboratory conditions. Feeding experiments also tested to what extent the egg capsule and lower levels of mechanical protection could deter predation and Multivariate Correspondence Analyses were performed to explore which feeding traits of the tested invertebrate species would explain the experimental results. Results showed predation on eggs by crabs and echinoderms equipped with certain prey capture methods that allowed them to feed on eggs. Also, the egg capsule appeared to provide protection from predation by certain species with less powerful prey capture tools. Prey capture tools of the tested species appeared to be the feeding trait that better explained the experimental results. Therefore, whether or not eggs were eaten in these experiments might be determined by a mechanical factor. Nonetheless this may not be the case for species that might not have fed on eggs due probably to a chemosensory question, not recognising them as food. This work thus contributes to the understanding of the ecology of early life stages of cuttlefish and the factors that can affect offspring survival and subsequently impact recruitment to the adult populations of this exploited species