Alpheid shrimps from the mangroves and mudflats of Singapore. Part I. Genera Salmoneus, Athanas and Potamalpheops, with the description of two new species (Crustacea : Decapoda : Caridea)

Extensive field collections of small alpheid shrimps in Sungei Buloh and Lim Chu Kang mangroves in Singapore, along with the examination of preserved material, yielded two new species and several new records for South-East Asia and Australia. The description of Salmoneus singapporensis, new species, is based on a single specimen from Singapore, which differs only slightly from the rarely collected S. rostratus Barnard. The latter species is recorded for the first time from Phuket, Thailand. Potamalpheops johnsoni, new species, is presently only known from Sungei Buloh, where it occurs syntopically with P. tigger Yeo & Ng. The new species can easily be distinguished from P. tigger by the presence of a subapical ventral tooth on the rostrum. The latter species is recorded for the first time from northern Australia. The differences in the length and shape of the rostrum and the length of the stylocerite observed in several species of Potamalpheops suggest a rather high plasticity of these structures in basal alpheids. Athanas polymorphus Kemp and A. japonicus Kubo, taxonomically problematic species or species complexes, are recorded for the first time from Singapore. The most remarkable feature of these two species is a pronounced polymorphism in the development of the first chelipeds.