A new Littoraria (Gastropoda : Littorinidae) from northwestern Australia

Abstract

Littoraria ianthostoma, n. sp. is described from mangrove forests in Joseph Bonaparte Gulf in northwestern Australia. The new species superficially resembles the widespread Littoraria articulata (Philippi, 1846), with which it is sympatric, but differs in the closed penial sperm duct and absence of a pseudotrich in the paraspermatozoa. Allozyme analysis confirms a large genetic distance between these two species and fixed allelic differences between sympatric samples. This discovery is surprising because the distribution and taxonomy of the mangrove-associated Littoraria of Australia had been considered well known. The anatomy and protoconch indicate that the new species produces pelagic egg capsules and undergoes planktotrophic development. Nevertheless, it has not been found outside Joseph Bonaparte Gulf and so appears to be the most narrowly distributed of the 39 members of the genus. Possible phylogenetic relationships of the new species and apparent isolation of Joseph Bonaparte Gulf are discussed.