La pêche électrique pratiquée dans les eaux intérieures des cinq archipels de la Polynésie française a permis d'inventorier 16 espèces de crustacés d'eaux douces. Parmi les 16 espèces mentionnées dans le présent article, une espèce est endémique: Caridina rapaensis de Rapa et de Rurutu. Six sont localisées dans la région Pacifique et neuf dans la région Indo-Ouest Pacifique. Une nouvelle espèce a été trouvée: Macrobrachium sp. Elle colonise les rivières de Moorea et des îles marquisiennes. Trois nouvelles espèces ont été pêchées pour la première fois en Polynésie française: Caridina serratirostris (Moorea et Tubuaï), Ptychognathus easteranus (Rurutu et Hiva Oa), Varuna litterata (Tahiti et Moorea). La répartition altitudinale de ces 16 espèces dans les îles étudiées a été établie et la biomasse des principales espèces dans les rivières de Tahiti-Moorea a été calculée.

Due to the sparse and unstable nature of insular freshwater habitats, marine larval dispersal of amphidromous species is considered a critical element of population persistence. We assessed population genetic structure of freshwater prawn Macrobrachium lar across its range that encompasses two biogeographic barriers: the vast open ocean separating Western and Central Pacific regions and the Indo-Malay archipelago separating Indian and Pacific oceans. A total of 173 samples collected from 21 islands throughout the Indo-Pacific were sequenced at 16S and 28S rDNA. We observed distinct genetic isolation of populations located at the eastern and southwestern edge of the species range but no evidence of an effect of the IndoPacific barrier. Differentiation patterns are consistent with a stepping-stone model of dispersal. Genetic differences of Central Pacific populations may reflect founder events associated with colonization of isolated islands, or be a signature of a past bottleneck after population depletion caused by drastic climatic events.

Anguillid eels were sampled from permanent rivers in the Ré union and Mauritius islands, western Indian Ocean, with a standardized electrofishing method. A. marmorata was very dominant, corresponding to 91.7 and 90.

External morphology has always been the first criterion used to separate species of shrimps, especially in the freshwater genus Caridina H. Milne-Edwards, 1837, but more doubts have been expressed regarding the relevance of some of the morphological characters. We collected 27 specimens of Caridina from seven different localities during field work conducted on the island of Pohnpei (Federated States of Micronesia). After genetic verification that they all belonged to the same species, 19 morphological variables were measured and correlated with the elevation of the collecting stations using correlation analyses. We provide evidence that the length of the rostrum 2 showed strong negative correlation with the elevation. This could be explained either by the physical stress exerted on the rostrum by the stronger water currents in the stations at a higher elevation, as a defence against predators in the lower stations, or a combination of both possibilities.The taxonomy of these shrimps is thus challenging and should not rely only on rostrum length, but on other characters such as the number of teeth on the dorsal margin of the carapace, which is not correlated with rostrum length and therefore, with the environment.

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