The complex study of complexes: The first well-supported phylogeny of two species complexes within genus Caridina (Decapoda: Caridea: Atyidae) sheds light on evolution, biogeography, and habitat.

Atyid shrimps, a key component of tropical freshwater ecosystems, face multiple anthropogenic threats and thus need special attention. With more than 300 described species, the genus Caridina is the most speciose of all the Caridea infra-order. Caridina spp. occupy diverse habitats in tropical freshwaters of the Indo-West Pacific region. Several species complexes have been recognized, based on common morphological features, but little is known about how well these morphological characteristics align with phylogenetic characteristics. Furthermore, no phylogeny of the genus Caridina published so far has provided well-resolved and supported relationships among different species, thus impeding the possibility of proposing evolutionary hypotheses. In this study we used next generation sequencing (NGS) to provide new insights into the phylogenetic relationships among the genus Caridina, focusing on two complexes: 'Caridina nilotica' and 'Caridina weberi'. We collected 92 specimens belonging to these two groups from most of their known geographical range, representing 50 species, for which we sequenced seven mitochondrial genes and two nuclear markers using ion torrent NGS. We performed a phylogenetic analysis, which yielded the first well-supported tree for the genus Caridina. On this tree were mapped the geographic ranges and the habitats used by the different species, and a time calibration was tested. We found the driving factors that most likely account for separation of clades are differences in habitat and to a lesser extent geography. This work provides new insights into the taxonomy of this group and identifies opportunities for further studies in order to fill knowledge gaps that currently impede the management and conservation of atyid species.

Elephantis, a new genus for Caridina natalensis Bouvier, 1925 from eastern rivers of Madagascar.

Elephantis, new genus, is established for Caridina natalensis Bouvier, 1925 hitherto known only from South Africa with one male specimen. Recently, three surveys by electric fishing (2004, 2008 and 2010) of some eastern rivers from Madagascar have permitted to discover numerous specimens of this species. Caridina natalensis is different from all other known species of Caridina by its remarkably broad endopod of the male first pleopod, a long clubbed appendix masculina on the male second pleopod reaching beyond distal end of endopod and strong third pereiopods. Therefore a new genus name is proposed for this species. In addition to detailed description of diagnostic morphological characters, molecular sequences obtained from mitochondrial 16S gene are provided for six specimens of this species. These DNA sequences are integrated to the 16S molecular phylogeny of atyid freshwater shrimps recently published by von Rintelen et al. (2012). Elephantis natalensis comb. nov. sequences formed a divergent group supported in maximum likelihood analysis. The availability of DNA samples could be used as reference and integrated in further phylogenetic studies on atyid freshwater shrimps.

Taxonomic study of the freshwater shrimps genus Atyoida Randall, 1840 (Crustacea: Decapoda: Atyidae) in Polynesia with a revalidation of A. tahitensis Stimpson, 1860.

Numerous specimens of Atyoida were collected in Polynesia during specific samplings led by the Muséum national d'Histoire naturelle (MNHN, Paris) from 1983 to 2017. In the context of an integrative taxonomy, all the Polynesian specimens were morphologically and genetically studied. The molecular study proved that the specimens were split in two different clades separated by 7% genetic distance (16S) and geographically structured that can be considered as two distinct species. In this article, A. tahitensis Stimpson, 1860 from Eastern Polynesia is re-validated as a distinct species from A. pilipes (Newport 1847) from Vanuatu to Marquesas archipelago. The morphological study, besides coloration patterns (Body blackish on its back, ornamented on its flanks with numerous bluish dots and longitudinal stripes for A. tahitensis; orange-yellow back as well as the antennular peduncle, telson and uropods with the flanks whitish ornamented with numerous blue-black patterns of various shapes for A. pilipes), did not allow us to find characters to distinguish easily the two species. Detailed re-descriptions and the geographical distribution of these two species are given and a neotype deposited in the MNHN (Paris) is designated for A. tahitensis.

Revalidation of Caridina natalensis De Man, 1908 (Crustacea: Decapoda: Atyidae) in the South Western Indian Ocean.

Numerous specimens of a freshwater shrimp with small eggs belonging to the Caridina nilotica complex collected in the South Western Indian Ocean were studied and compared with recent and old collection specimens genetically (16S mitochondrial analysis for recent and type specimens) and morphologically. The results revealed that, in the Indian Ocean, what has been identified by several authors under various species names of the complex C. nilotica, was in fact C. natalensis De Man, 1908. This valid species is re-described and compared with closely related species, often confused with it in this area: C. brachydactyla De Man, 1908, C. brevidactyla Roux, 1920, C. gracilipes De Man, 1892 and C. longirostris H. Milne Edwards, 1837.

Description of a new species of Caridina (Crustacea: Decapoda: Atyidae) from two Micronesian islands (Guam and Babeldaob).

During field trips to Guam and Babeldaob Islands in Micronesia, freshwater shrimps were sampled and assigned either to Caridina brachydactyla De Man, 1908 or C. mertoni J. Roux, 1911 (Decapoda: Atyidae), following previous inventories. In combining morphological data with a genetical analysis, it appeared that all the specimens belonged to a new species, Caridina variabilis sp. nov., here described with its distribution. The status of this new species is clarified and finally, neither C. brachydactyla, nor C. mertoni occur in these two islands. DNA sequences of 16S were obtained from the syntypes of C. mertoni.