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Caridean prawns of the genus Macrobrachium Bate, 1868 (Crustacea, Decapoda, Palaemonidae) collected from the Laotian river system were studied. Fourteen species are recognised in this study, including one unidentified species. Their taxonomy is discussed and illustrated, of which 11 species are new records to the Laotian fauna. The identity of species of the “M. dienbienphuense” group has been remained obscure, and this study, which incorporated the 16S rRNA mitochondrial gene analysis, demonstrated that M. amplimanus Cai & Dai, 1999, M. dienbienphuense Dang & Nguyen, 1972, and M. eriocheirum Dai, 1984 are valid species. The Macrobrachium fauna in Laos exhibited closer affinity to that of the tropical Indo-China and Sunda elements (southern Yunnan Province, south-western China, northern Vietnam as well as north and north-eastern Thailand), implying that the Mekong River system contributes substantially to the regional freshwater prawn biodiversity.

The first internal transcribed spacer (ITS-1) of nuclear ribosomal DNA and mitochondrial DNA 16S rRNA were amplified by Polymerase chain reaction (PCR) using genomic DNA extracted from adult tissue of four species of Scylla spp. and the first zoeal stages of S. serrata, S. paramamosain and S. olivacea as template. Using the ITS-1 region, variation in product fragment length was found to be useful for distinguishing S. serrata and S. olivacea from two other species. The other two species (S. paramamosain and S. tranquebarica) could be identified using the restriction endonuclease Hha I. Using 16S rDNA, all four species were identified using PCR-restriction fragment length polymorphism (RFLP) by double digestion with DraI and HindIII. These genetic markers can be used for hybridization breeding studies and in field studies of larval and juvenile mud crabs of the genus Scylla.

The pronghorn spiny lobster, Panulirus penicillatus, is a circumtropical species which has the widest global distribution among all the species of spiny lobster, ranging throughout the entire Indo-Pacific region. Partial nucleotide sequences of mitochondrial DNA COI (1,142–1,207 bp) and 16S rDNA (535–546 bp) regions were determined for adult and phyllosoma larval samples collected from the Eastern Pacific (EP)(Galápagos Islands and its adjacent water), Central Pacific (CP)(Hawaii and Tuamotu) and the Western Pacific (WP)(Japan, Indonesia, Fiji, New Caledonia and Australia). Phylogenetic analyses revealed two distinct large clades corresponding to the geographic origin of samples (EP and CP+WP). No haplotype was shared between the two regional samples, and average nucleotide sequence divergence (Kimura's two parameter distance) between EP and CP+WP samples was 3.8±0.5% for COI and 1.0±0.4% for 16S rDNA, both of which were much larger than those within samples. The present results indicate that the Pacific population of the pronghorn spiny lobster is subdivided into two distinct populations (Eastern Pacific and Central to Western Pacific), with no gene flow between them. Although the pronghorn spiny lobster have long-lived teleplanic larvae, the vast expanse of Pacific Ocean with no islands and no shallow substrate which is known as the East Pacific Barrier appears to have isolated these two populations for a long time (c.a. 1MY).