Contributions to Zoology, 79 (2) – 2010Bastian T. Reijnen; Bert W. Hoeksema; Edmund Gittenberger: Host specificity and phylogenetic relationships among Atlantic Ovulidae (Mollusca: Gastropoda)

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Introduction

Ovulid snails are obligate associates of Cnidaria. As far as known, most occur associated with octocorals (Anthozoa: Octocorallia: Alcyonacea), but in both the Caribbean and the Indo-Pacific some ovulid species feed on antipatharians (Anthozoa: Hexacorallia: Antipatharia) (Tazioli et al., 2007). The species of Pedicularia Swainson, 1840, that have been classified with the Ovulidae for a long time (Goud and Hoeksema, 2001), live on stylasterid corals (Hydrozoa: Athecatae: Filefera). Pedicularia differs from the undisputed ovulids in radula morphology (Simone, 2004); it is now classified in the separate family Pediculariidae (Fehse, 2007; Lorenz and Fehse, 2009).

Thirty-seven species of Ovulidae Fleming, 1822, are known from the Caribbean and Atlantic area (Lorenz and Fehse, 2009). The dominant genus in the Caribbean is Cyphoma Röding, 1798, with 14 species of which Cyphoma gibbosum (Linnaeus, 1758) is the most common. Due to the low number of ovulid species in the Caribbean and the well-known diversity of Octocorallia (Bayer, 1961) parasite/host relationships are most easily studied here.

It has been hypothesized that colour patterns and texture of ovulid mantles may either mislead potential predators by mimicking its host’s branches and polyps, or that its colour acts as a warning of unpalatability (aposematic species) (Rosenberg, 1992; Schiaparelli et al., 2005). Snails closely resembling coral branches and polyps of their host may be camouflaged in such a way that they are almost undetectable for predators, such as shown by the Caribbean Cymbovula acicularis (Lamarck, 1810), which uses its mantle colour and protrusions to mimic the branches and polyps of its gorgonian host (Fig. 1d).

As a first step to a better understanding of the associations between alcyonaceans and ovulids, Yamamoto (1972) and Schiaparelli et al. (2005) studied the snails and their hosts in the Indo-Pacific. In the present paper we primarily deal with the Ovulidae and their octocoral hosts of the Caribbean island of Curaçao. Our new data on species associations are used to investigate whether the gastropod species should be considered generalists or specialists. Based on of the molecular data from this study and GenBank, a provisional molecular phylogeny reconstruction of Ovulidae is presented.

FIG2

Fig. 1. Species in situ. a) Cyphoma gibbosum; b) C. signatum; c) C. gibbosum (juvenile); d) Cymbovula acicularis; e) Simnialena uniplicata (juvenile).