Shell‐bearing Mollusca (Bivalvia and Gastropoda) from submarine caves in Hong Kong

Abstract

In October 2002, the Hong Kong Marine Caves Expedition was convened jointly by the Swire Institute of Marine Science, The University of Hong Kong and the Natural History Museum, London. The expedition explored the marine cave habitats of Hong Kong and their fauna. This paper describes the diversity of marine cave molluscs collected using SCUBA from two marine caves at Conic Island and Steep Island in the eastern waters of Hong Kong. Twenty, and eight species of shell‐bearing epifaunal bivalves and gastropods, respectively, were collected from the ceilings and walls of the two caves. Another 11 infaunal bivalve species were collected from the sediment‐filled floors of the caves. Of the species identified, eight are new records for Hong Kong. These are the bivalves Spondylus anacanthus, Hiatella cf. orientalis, Panomya turgida, Nuculana sp., Abra cf. fujitai, Pinguitellina cf. nux, and Lyonsiella cf. parva, and the epitonid gastropod Epitonium bullatum. The epibenthic molluscs recorded during this survey were mostly adults whereas the endobenthic bivalves were all juveniles. Although the above species are recorded from Hong Kong for the first time, they have been identified from non‐cave habitats elsewhere. In particular, the often singular presence of juvenile infaunal bivalves in the cave sediments suggests their opportunistic colonization by such species and thus further evidence for a lack of endemicity. That the epibenthic molluscs are non‐endemic is probably also because Hong Kong's submarine caves are very modern, that is, Middle Holocene.