A new genus and new species of potamid crab, Indawmon thanayei, is described from Indawgyi Lake in Kachin State, Myanmar. The taxon is characterised mainly by its male first gonopod structure which has the terminal and subterminal segments not clearly demarcated, with the terminal segment subcylindrical in shape, gradually tapering to a sharp tip and is bent at an angle of about 45-90 degrees. The new genus is compared with Indochinamon and Shanphusa, which it superficially resembles. The genetic data (based on the mitochondrial 16S rDNA) also supports the establishment of the new taxa.

A new species of freshwater crab, Potamiscus whitteni, is described from Chin State in western Myanmar. It is morphologically most similar to P. rangoonensis (from Yangon, Myanmar) and P. palelensis (from Manipur, India), but can easily be distinguished by the carapace features and male first gonopod structure.

The potamid freshwater crab, Inlethelphusa acanthica (Kemp, 1918), is endemic to Inle Lake, in Shan state, Myamnar, and was hitherto known only from the types and several small specimens collected in the 1930s. The species, the type of Inlethelphusa Yeo & Ng, 2007, is redescribed from a good series of fresh specimens. The taxonomy of the species is discussed and variations in the armature of the carapace kunerolateral margin, male pleon, chela, as well as the male first gonopod structure are documented. Significantly, the male first gonopod of smaller specimens has the terminal segment straight and more cylindrical, with the tip truncate or weakly bifurcated, in contrast to that of larger males, which is more elongate, with the distal part gently curved upwards and the tip sharp.

Myanmar is abundant in lakes and rivers, yet only a few investigations on the fauna of shrimps and prawns have been conducted and no molecular characteristics of prawn species have been described. This study reveals the morphologically identification of five freshwater prawn species under the genus Macrobrachium, including M. cavernicola, M. australiense, M. johnsoni, M. josephi and Macrobrachium sp.WMY-2017. As there was no previous record and information concerning with M. australiense, M. johnsoni, M. josephi and Macrobrachium sp. WMY-2017, they were regarded as the first record from Myanmar. A fragment of Mitochondrial Cytochrome Oxidase I Gene (COI) was amplified successfully from three studied species: M. australiense, M. josephi, and Macrobrachium sp.WMY-2017. The interspecific divergences of studied species varied from 0.01 to 0.15. The phylogenetic tree based on COI fragment sequences showed that M. australiense was closely related to M. rosenbergii, while Macrobrachium sp. WMY-2017 was closest to M. josephi. The results of molecular phylogeny has clarified the relationship within the genus Macrobrachium and represents the first step toward understanding the pattern of speciation base on molecular approach in Myanmar.