A B S T R A C TMacrobrachium jelskii (Miers, 1877) occurs in all major Brazilian drainage basins. Considering its wide distribution and the supposed isolation of certain populations, we evaluated phylogenetic relationships among populations from several river basins. Analyses of molecular data using the mitochondrial COI and 16S genes suggest the division of the species into two clades, "Amazonian" and "coastal." The genetic divergence between these two groups is greater than the genetic divergence within the respective groups. Based on the time of divergence and the probable natural distribution of the species, we suggest two evolutionary scenarios to explain the origin of the coastal clade. The first scenario considers the capacity of M. jelskii to tolerate saline environments. The second is based on Pliocene climate changes that would have caused river confluence from sea level regression. The two clades occur sympatrically but this is a recent condition. The wide geographic distribution and low genetic divergence of the Amazonian clade allows us to propose that the current distribution of M. jelskii is partly due to human activity. Pending future analysis, the absence of a consistent morphological synapomorphy precludes the description of a new cryptic taxonomic entity for M. jelskii.
Macrobrachium jelskii is a freshwater shrimp endemic to South America, occurring in all major Brazilian basins. It is used in various activities, such as fishing, fishkeeping and even as food for humans and animals, and therefore its distribution is affected by anthropic influence. Misidentification of M. jelskii is recurrent because of its morphological similarity to some sympatric species such as M. amazonicum and M. acanthurus. Thus, the aim of this study is to redescribe M. jelskii, proposing some characteristics that allow for a clearer differentiation of this species when compared to other similar congeneric species that occur in South America. The informative characters were the size and the shape of the rostrum, the ratio of the carpus and chela, the ratio of the chela and carapace length and the shape of the carpus of the second pereiopod, as well as the ratio between the length of the internal pair of posterior spine of telson and median apex of the posterior margin of telson. Although the intraspecific variability is high, the combination of the characters mentioned herein, including a morphological key, is very useful and makes it easier to differentiate between these three species.
This checklist is the fourth contribution resulting from a long-term multidisciplinary project which combined morphological analyses and molecular techniques (mitochondrial DNA markers) for accurate identification of marine and coastal decapod crustaceans of São Paulo State (Brazil). We provide a list of 63 species of the following 11 families of 4 superfamilies of Anomura: Albuneidae (4 spp.), Blepharipodidae (1 sp.), Chirostylidae (1 sp.), Diogenidae (18 spp.), Hippidae (1 sp.), Munididae (8 spp.), Munidopsidae (1 sp.), Paguridae (13 spp.), Parapaguridae (2 spp.), Porcellanidae (13 spp.), and Pylochelidae (1 sp.). Seven species previously reported from the region were neither collected nor found in museum collections during our study, including one (Sympagurus dimorphus) that we suggest to be removed from São Paulo coast fauna lists. We generated new sequences of cytochrome oxidase subunit I (barcode region) and 16S genes of 44 species. This anomuran inventory may serve as guideline for future studies on taxonomy, conservation, population genetics, biogeography, and phylogenetics, which might flag species that deserve further investigations and concerns.
The genera IsochelesStimpson, 1858 and LoxopagurusForest, 1964 are endemic to America and occur in tropical and subtropical waters. There are five species of Isocheles, two of them are found in the Western Atlantic (I. sawayaiForest & de Saint Laurent, 1968 and I. wurdemanniStimpson 1859) and three in the Eastern Pacific (I. pilosus (Holmes, 1900), I. pacificusBouvier, 1907, and I. aequimanus (Dana, 1852)). Loxopagurus is a monotypic genus and occurs only in southeastern South America. These two genera are morphologically similar, with differences in shape and size of chelae. The published information on the taxonomy of these genera is scant, and there have been some recent doubts about their phylogenetic relationship. Our study aimed to elucidate the phylogenetic relationship of Isocheles and Loxopagurus and evaluate their taxonomic validity and contextualization in Diogenidae Ortmann, 1892. We performed an integrative analysis using multigene data (16S rRNA, COI, and H3) and a detailed morphological evaluation, including redescriptions, seeking characters that allow the clear identification of these species. The type specimens of I. aequimanus, I. pilosus, and L. loxochelis (Moreira, 1901) were lost and errors are common regarding the identification of the species of Isocheles. Characters that clearly delimit these species, such as the ornamentation and shape of the chelipeds and the number of teeth on the second article of the antenna, were stated. The morphological and molecular analyses corroborated the taxonomical validity of Isocheles and Loxopagurus as two distinct genera based on the differences of the shield and chelipeds, on the topology of the trees, and on the genetic divergence inferred from three molecular markers. We also verified that the five amplified species of Isocheles constitute five distinct clades and described a new species of Isocheles, using both molecular and morphological differences from congeners. An identification key for Isocheles is proposed. Although the type material of two out of the five species of Isocheles and the holotype of Loxopagurus loxochelis were lost, the designation of neotypes is not recommended in these cases.
Potimirim is one of the 40 genera of Atyidae restricted to America, which occurs in coastal freshwater habitats and questions about population status and variability have been emerging. Potimirim brasiliana occurs in Brazil from the northeastern to southeastern region. In order to evaluate the hypothesis of genetic structure among populations, we performed molecular analyses with specimens from all known limit of distribution of the species. The molecular markers used were COI and 28S. Phylogenetic trees were obtained by maximum likelihood and Bayesian analyses, and a haplotype network was obtained based only on COI. We found clear separation between P. brasiliana, P. potimirim, P. glabra and Potimirim sp 2. No pattern of structuration was found among P. brasiliana, but the haplotype network showed geographic pattern of structuration for the congener P. potimirim. The lack of genetic structuration among P. brasiliana can be explained by its life cycle that requires brackish water to complete their larval development. The larvae and juvenile in contact with these habitats can spread through oceanic currents, especially in higher rainfall seasons, maintaining the gene fl ow. The explanation for the geographical pattern found among P. potimirim is still missing and aspects about its lifecycle and larval development should be investigated.
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