Leonardo G. Pileggi

Molecular phylogeny of the freshwater prawn genus Macrobrachium (Decapoda, Palaemonidae), with emphasis on the relationships among selected American species

The genus Macrobrachium Bate, 1868 is one of the best examples of widespread crustacean genera distributed globally throughout tropical and subtropical waters. Previous investigators have noted the systematic complexity of the group, and have suggested rearrangements within the family Palaemonidae. Our phylogenetic analysis of new mitochondrial DNA sequences of 58 species of Macrobrachium distributed mainly in America support the hypothesis of monophyly of this genus, if Cryphiops Dana, 1852 is accepted as a generic synonym. We concluded that the independent evolution of different types of life cycle (abbreviated larval development – ALD and extended larval development – ELD) must have occurred more than once in the history of the group. Similarly, we also concluded that the current type species of the genus, Macrobrachium americanum Bate, 1868, should not be considered valid, as previously proposed. The synonymy of two members of the ‘olfersi’ species complex (M. birai Lobao, Melo & Fernandes, 1986 and M. holthuisi Genofre & Lobao, 1978) with M. olfersi (Wiegmann, 1836) was confirmed. Similar results were found in comparing M. petronioi Melo, Lobao & Fernandes, 1986 and M. potiuna (Muller, 1880), in which the genetic divergence placed M. petronioi within the level of intraspecific variation of M. potiuna. The taxonomic status of the genus Cryphiops, as well as theories on the origin of Macrobrachium, is also called into question.

Taxonomic revision of doubtful Brazilian freshwater shrimp species of genus Macrobrachium (Decapoda, Palaemonidae)

Os camaroes de agua doce do genero Macrobrachium Spence Bate, 1868 encontram-se amplamente distribuidos em rios de regioes tropicais e subtropicais e representam um grupo com taxonomia controversa. Os caracteres morfologicos comumente utilizados para separacao de especies apresentam uma grande variacao intraespecifica. Duvidas sobre o status taxonomico de M. birai Lobao, Melo & Fernandes, 1986, M. holthuisi Genofre & Lobao, 1978 e M. petronioi Melo, Lobao & Fernandes, 1986 foram levantadas devido a alta similaridade morfologica das primeiras com relacao a M. olfersi (Wiegmann, 1836) e da ultima com relacao a M. potiuna (Muller, 1880). Assim, foi realizada uma analise morfologica detalhada de tais especies, incluindo novos caracteres comumente nao utilizados na identificacao dos taxons. A partir dos resultados obtidos, juntamente com dados moleculares, concluimos que M. birai e M. holthuisi sao sinonimos-junior de M. olfersi, e M. petronioi e sinonimo-junior de M. potiuna. Portanto, considerando-se tais sinonimias, sao reportadas 17 especies validas para o territorio brasileiro.

Molecular barcode and morphological analyses reveal the taxonomic and biogeographical status of the striped-legged hermit crab species Clibanarius sclopetarius (Herbst, 1796) and Clibanarius vittatus (Bosc, 1802) (Decapoda : Diogenidae)

Abstract. The taxonomic status of the species Clibanarius sclopetarius (Herbst, 1796) and Clibanarius vittatus (Bosc, 1802), which have sympatric biogeographical distributions restricted to the western Atlantic Ocean, is based only on differences in the colour pattern of the walking legs of adults. Their morphological similarity led to the suggestion that they be synonymised. In order to investigate this hypothesis, we included species of Clibanarius Dana, 1892 in a molecular phylogenetic analysis of partial sequences of the mitochondrial 16S rDNA gene and the COI barcode region. In addition, we combined the molecular results with morphological observations obtained from several samples of these two species. The genetic divergences of the 16S rDNA and COI sequences between C. sclopetarius and C. vittatus ranged from 4.5 to 5.9% and 9.4 to 11.9%, which did not justify their synonymisation. Differences in the telson morphology, chela ornamentation, and coloration of the eyestalks and antennal peduncle provided support for the separation of the two species. Another interesting result was a considerable genetic difference found between populations of C. vittatus from Brazil and the Gulf of Mexico, which may indicate the existence of two homonymous species.

Molecular perspective on the American transisthmian species of Macrobrachium (Caridea, Palaemonidae).

Abstract The closure of the Isthmus of Panama (about 3.1 million years ago) separated previously continuous populations and created two groups of extant species, which live now in the Pacific and Atlantic drainage systems. This relatively recent event was a trigger to diversification of various species in the Neotropics, nonetheless there are exemplars that do not show sufficient morphologic variability to separate them by traditional morphological tools. About 60 years ago, some freshwater decapod species with high morphological similarity were separate by previous researchers, based on geographical distribution, in Pacific and Atlantic and considered as “sister species”. However, the complete isolation of these prawns by this geographical barrier is questionable, and it has generated doubts about the status of the following transisthmian pairs of sibling species: Macrobrachium occidentale × Macrobrachium heterochirus, Macrobrachium americanum × Macrobrachium carcinus, Macrobrachium digueti × Macrobrachium olfersii, Macrobrachium hancocki × Macrobrachium crenulatum, Macrobrachium tenellum × Macrobrachium acanthurus and Macrobrachium panamense × Macrobrachium amazonicum. Here we evaluated the relation among these pairs of sibling species in a molecular phylogenetic context. We generated 95 new sequences: 26 sequences of 16S rDNA, 25 of COI mtDNA and 44 of 18S nDNA. In total, 181 sequences were analyzed by maximum likelihood phylogenetic method, including 12 Macrobrachium transisthmian species, as well as seven other American Macrobrachium species, and two other palaemonids. Our analysis corroborated the morphological proximity of the sibling species. Despite the high degree of morphological similarities and considerable genetic diversification encountered among the transisthmian sister species, our data support the conclusion that all species included in sibling groups studied herein are valid taxonomic entities, but not all pairs of siblings form natural groups.

Inferring population connectivity across the range of distribution of the stiletto shrimp Artemesia longinaris Spence Bate, 1888 (Decapoda, Penaeidae) from DNA barcoding: implications for fishery management

Abstract Artemesia longinaris is a marine shrimp endemic to the southwestern Atlantic and distributed from Atafona, Rio de Janeiro (Brazil) to Rawson, Chubut (Argentina). In recent years, this species has become an important target of the commercial fishery as a consequence of the decline in the fishery of more traditional and profitable marine shrimps. In addition, phenotypic variations have been documented in populations along its distribution. Therefore, investigations on the genetics of the fishing stocks are necessary for the development of sustainable management strategies and for understanding the possible sources of these variations. The mitochondrial gene Cytochrome Oxidase I (COI) was used to search for evidence of genetic structure among the populations of Artemesia longinaris and to analyze the phylogenetic relationships among them. A total of 60 specimens were collected from seven different localities, covering its geographical range. The final alignment showed 53 haplotypes (48 individuals and 5 shared), with no biogeographical pattern. The low genetic divergence found, with a non-significant FST value, also suggests the absence of population structure for this gene. These findings indicate a continuous gene flow among the populations analyzed, suggesting that the phenotypic variation is a consequence of different environmental conditions among the localities.

Crustacea, Decapoda, Palaemonidae, Macrobrachium Bate, 1868, São Sebastião Island, state of São Paulo, southeastern Brazil

Macrobrachium is distributed globally in most biogeographical regions, and contains species with interesting mechanisms of evolution. We conducted an exhaustive survey on Sao Sebastiao Island, the largest coastal island of the state of Sao Paulo. Here we provide a list of species ( M. acanthurus , M. carcinus , M. heterochirus , M. olfersi , M. potiuna ) together with the diagnosis, distribution, and remarks on each species, and a key for their identification. We compare our findings with available information on the genus. The high diversity of freshwater shrimps on the island is interesting in terms of biogeographical and evolutionary processes.