New findings of rare or little-known alpheid shrimp genera (Crustacea, Decapoda) in Moorea, French Polynesia

Six rare or little-known genera from the shrimp family Alpheidae are reported from French Polynesia, five of them for the first time. Distribution ranges are significantly extended for the recently described Acanthanas pusillus Anker, Poddoubtchenko & Jeng, 2006 and Richalpheus palmeri Anker & Jeng, 2006, previously known only from two and one type specimens, respectively, from the Philippines. The original description of A. pusillus, based on two females, is completed with the description and illustration of the male cheliped and pleopod; accordingly, the diagnosis of Acanthanas is slightly emended. The genus Leptalpheus Williams, 1965 was not known from French Polynesia before, but is represented there by two species: L. denticulatus Anker & Marin, 2009, previously known from Vietnam, the Philippines and Fiji; and L. pacificus Banner & Banner, 1974, previously considered as a Hawaiian endemic. The genus Prionalpheus Banner & Banner, 1960 is represented in French Polynesia by two species: P. triarticulatus Banner & Banner, 1960, reported for the first time, and P. brachytomeus Banner & Banner, 1971, reported with some doubts (P. cf. brachytomeus) for the first time since the original description. Rugathanas borradailei (Coutière, 1903), a widespread but rather uncommon and easily overlooked species, is also reported for the first time from French Polynesia. Colour patterns are illustrated for all species, this being for the first time for R. palmeri, L. pacificus, P. triarticulatus and P. cf. brachytomeus.