Distinct protoconchs recognised in three of the larger Mediterranean Cerithium species (Caenogastropoda: Cerithiidae)

ABSTRACT

The gastropod genus Cerithium includes several polymorphic species which are hardly distinguishable using a morphological approach based on teleoconch characters. Here we show that protoconch characters can be reliably used to identify the larger Mediterranean species (Cerithium alucastrum, C. repandum and C. vulgatum), and to assess their intraspecific variability. Based on a large amount of morphological data, we show that a multispiral, strongly sculptured protoconch (traditionally associated with C. vulgatum) is found in C. alucastrum. This species originated in the Pliocene. A multispiral, weakly sculptured protoconch, not observed previously, is reported for C. vulgatum. A paucispiral protoconch, distinct from those observed previously for C. lividulum and C. renovatum, is reported for C. repandum and can be used for recognising its wide intraspecific variation and understanding its geographical distribution. Cerithium repandum, previously doubtfully recorded outside its type locality, extends back to the mid-Pliocene and is today rather widely distributed in the Mediterranean, although absent from the Aegean Sea and the Alboran Sea. We describe the larval development of C. repandum and C. vulgatum for the first time, confirming their respective non-planktotrophic and planktotrophic development previously inferred from protoconch morphology. Also, we report a possible case of morphological convergence between C. repandum and C. vulgatum occurring in harbour sites, where we found a distinct (possibly Anthropocene) shell form not described previously from other Recent or fossil material.

KEYWORDS:

• Anthropocene
• biogeography
• ecophenotypes
• Gastropoda
• larval development
• Pleistocene
• Pliocene
• taxonomy

Acknowledgements

The first author warmly thanks Marie-Catherine Boisselier (MNHN) for her scientific support during this research at MNHN (Paris, France). We thank Gianni Spada (Paris, France) and Stefano Palazzi (Milo, Catania, Italy) for providing several specimens now housed in the MNHN or still under study by the first author. Our thanks also to Anders Warén (Stockholm, Sweden), who made available many Cerithium specimens housed at SMNH. Bruno Sabelli (University of Bologna, Italy) and David G. Reid (Natural History Museum, London) are thanked for helpful discussions. D.G. Reid also provided useful references. Stefano Dominici (University of Florence, Italy) is thanked for providing information on the stratigraphy of sites in Tuscany. Thanks to Alberto Cecalupo (Milano), who very generously provided useful literature. We are very grateful to Alan Beu (GNS Science, Lower Hutt, New Zealand) for critically reviewing our English, and to Winston Ponder, Don Colgan (Australian Museum, Sydney) and two anonymous referees for their very constructive comments on the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Vittorio Garilli http://orcid.org/0000-0001-8809-4176

Daniela Parrinello http://orcid.org/0000-0001-9224-7737

Additional information

Funding

The contribution of the first author was partially carried out at the MNHN (Paris, France) thanks to funding by the European Commission [contract no. ENV4-CT98-5125].