Documenting decapod biodiversity in the Caribbean from DNA barcodes generated during field training in taxonomy

A new mud shrimp of the genus Paragourretia Sakai, 2004, from the Gulf of Mexico (Crustacea: Decapoda: Ctenochelidae)

A new western Atlantic member of the ctenochelid genus Paragourretia Sakai, 2004 is described to accommodate a single unique specimen collected by dredge on muddy rubble substrates of the continental shelf in the southwestern Gulf of Mexico. Paragourretia sandrae n. sp. closely resembles Paragourretia biffari (Blanco Rambla & Liñero Arana, 1994), another regionally reported species for which photographs and additional illustrations are herein provided. While P. biffari and P. sandrae n. sp. are similar in habitus and known habitat to the more commonly encountered confamilial Dawsonius latispina (Dawson, 1967), the third maxillipeds in Paragourretia bear distinct exopods that are absent in Dawsonius Manning & Felder, 1991. As in eight other world congeners, P. sandrae n. sp. differs from both P. biffari and Dawsonius in lacking triangular ventrolateral projections on the sixth pleomere. It is further distinguished from P. biffari by lacking a distinctly incised notch in the anterodistal margin of the uropodal exopod and by absence of a median terminal spine on the telson. Additional sequence-quality specimens of P. sandrae n. sp. are required to clarify its relationships within the polyphyletic genus Paragourretia on a molecular genetic basis.

Evidence of cryptic diversity in freshwater Macrobrachium prawns from Indochinese riverine systems revealed by DNA barcode, species delimitation and phylogenetic approaches

The diversity of Indochinese prawns in genus Macrobrachium is enormous due to the habitat diversification and broad tributary networks of two river basins: the Chao Phraya and the Mekong. Despite long-standing interest in SE-Asian decapod diversity, the subregional Macrobrachium fauna is still not yet comprehensively clarified in terms of taxonomic identification or genetic diversification. In this study, integrative taxonomic approaches including morphological examination, DNA barcoding, and molecular species delimitation were used to emphasize the broad scale systematics of Macrobrachium prawns in Indochina. Twenty-seven nominal species were successfully re-verified by traditional and molecular taxonomy. Barcode gap analysis supported broad overlapping of species boundaries. Taxonomic ambiguity of several deposited samples in the public database is related to inter- and intraspecific genetic divergence as indicated by BOLD discordance. Diagnostic nucleotide positions were found in six Macrobrachium species. Eighteen additional putative lineages are herein assigned using the consensus of species delimitation methods. Genetic divergence indicates the possible existence of cryptic species in four morphologically complex and wide-ranging species: M. lanchesteri, M. niphanae, M. sintangense, and some members of the M. pilimanus group. The geographical distribution of some species supports the connections and barriers attributed to paleo-historical events of SE-Asian rivers and land masses. Results of this study show explicitly the importance of freshwater ecosystems in Indochinese subregions, especially for the Mekong River Basin due to its high genetic diversity and species composition found throughout its tributaries.

Molecular phylogeny and species delimitation of the freshwater prawn Macrobrachium pilimanus species group, with descriptions of three new species from Thailand

Specific status and species boundaries of several freshwater prawns in the Macrobrachium pilimanus species group remain ambiguous, despite the taxonomic re-description of type materials and additional specimens collected to expand the boundaries of some species. In this study, the "pilimanus" species group of Macrobrachium sensu Johnson (1958) was studied using specimens collected from montane streams of Thailand. Molecular phylogenetic analyses based on sequences of three molecular markers (COI, 16S and 18S rRNA) were performed. The phylogenetic results agreed with morphological identifications, and indicated the presence of at least nine putative taxa. Of these, six morphospecies were recognised as M. malayanum, M. forcipatum, M. dienbienphuense, M. hirsutimanus, M. eriocheirum, and M. sirindhorn. Furthermore, three morphologically and genetically distinct linages were detected, and are described herein as M. naiyanetri Siriwut sp. nov. , M. palmopilosum Siriwut sp. nov. and M. puberimanus Siriwut sp. nov. The taxonomic comparison indicated wide morphological variation in several species and suggested additional diagnostic characters that are suitable for use in species diagnoses, such as the shape and orientation of fingers, the rostrum form, and the presence or absence of velvet pubescence hairs and tuberculated spinulation on each telopodite of the second pereiopods. The "pilimanus" species group was portrayed as non-monophyletic in both ML and BI analyses. The genetic structure of different geographical populations in Thailand was detected in some widespread species. The species delimitation based on the four delimitation methods (BIN, ABGD, PTP and GMYC) suggested high genetic diversity of the "pilimanus" species group and placed the candidate members much higher than in previous designations based on traditional morphology. This finding suggests that further investigation of morphological and genetic diversity of Southeast Asian freshwater prawns in the genus Macrobrachium is still required to provide a comprehensive species list to guide efforts in conservation and resource management.