Chitons (Mollusca, Polyplacophora) from the Maldive islands

Abstract

This paper is the first comprehensive and illustrated account of living Polyplacophora from the Maldive Islands. The only important previous contribution is that of E.A. Smith (1903), describing eight species. We determined 15 species sourced from 24 sampling sites, mainly at a depth of 20–40 meters, represented by 19 living specimens and 1112 valves. Only nine species (Parachiton hylkiae mauricejayi, Ischnochiton albinus, Ischnochiton sp., Rhyssoplax maldivensis, Tegulaplax hululensis, Lucilina sp., Acanthochitona penicillata, Craspedochiton cf. laqueatus, Cryptoplax burrowi) are represented by living specimens, the others by separate valves (Callochiton clausadeae, Lucilina perligera, L. carnosa, Acanthochitona sp., Craspedochiton sp., Cryptoplax sykesi), three of them (Lucilina perligera, Acanthochitona sp., Craspedochiton sp.) by only one or two valves. We did not find four of the species previously reported for the Maldives, i.e. Ischnochiton feliduensis, Callochiton platessa, Squamopleura miles and Schizochiton incisus. The specimen collected by J.S. Gardiner, and reported in Smith (1903) as Callochiton platessa Gould, has been studied, and it is not possible to attribute to any of the other Callochiton species from the Indian Ocean. It thus remains undetermined as Callochiton sp., and Callochiton platessa Gould must be deleted from the list of chiton species living in the Maldive Islands. The holotype of Ischnochiton feliduensis (the only specimen known) is illustrated to provide a complete and exhaustive survey of all the 19 chiton species now known from the Maldive Islands. Two species from other localities, Squamopleura miles and Schizochiton incisus, also are illustrated. The type material of Craspedochiton laqueatus and Cryptoplax burrowi has been examined. Eleven species are reported for the first time for the Maldives: Parachiton hylkiae mauricejayi, Ischnochiton albinus, Ischnochiton sp., Callochiton clausadeae, Lucilina perligera, L. carnosa, Lucilina sp., Acanthochitona penicillata, Acanthochitona sp., Craspedochiton sp. and Cryptoplax sykesi.