Cryptic diversity of chemosymbiotic bivalves: A systematic revision of worldwide Anodontia (Mollusca: Bivalvia: Lucinidae)

Abstract

Marine bivalves of the family Lucinidae possess a likely obligate chemosymbiosis with sulphide‐oxidising bacteria from which they derive much of their nutrition. Molecular analysis has shown that species of the ’Anodontia’ group form a distinct clade within the monophyletic Lucinidae. Species identification of the largely tropical ’Anodontia’ group, has been confused because of the white, sub‐spherical, smooth, toothless shells, with the name Anodontia edentula used uncritically for most Indo‐West Pacific species. Preliminary morphological analysis also showed that the group was much more diverse than previously realised. The present systematic revision of the world Anodontia species, based on museum collections, field sampling, anatomical and molecular data, now recognises 25 species (eight of these new). These species are divided into eight subgenera (four of these, Euanodontia, Afrophysema, Crytophysema and Bythosphaera are new) on the basis of shell morphology, corroborated by some molecular data. Two species are known from the tropical eastern Pacific, two from the Western Atlantic, five from the eastern Atlantic and 16 from the Indo‐West Pacific. Two new genera, Neophysema (type species N. aphanes sp. nov.) and Leucosphaera (type species Loripinus salamensis Thiele & Jaeckel, 1931), are proposed for species previously confused with Anodontia.