Checklist of decapod crustaceans from the coast of the São Paulo state (Brazil) supported by integrative molecular and morphological data: V. Dendrobranchiata and Pleocyemata [Achelata, Astacidea, Axiidea, Caridea (Alpheoidea and Processoidea excluded), Gebiidea, Stenopodidea]

A review of deep-sea shrimps (Decapoda: Dendrobranchiata and Caridea) with four new records for Venezuela

Different explorations have been made in deep waters of the oceans, some of them have included the Caribbean Sea and Venezuela from Albatros R / V in 1884 to Fridtjof Nansen R / V in 1988. Material from the Fridtjof Nansen R/V expeditions in Venezuela's coasts in 1988 were identified. From a total of 25 species, 4 are first reports for Venezuela: Plesionika tenuipes (Smith, 1881), Plesionika longicauda (Rathbun, 1901), Plesionika martia (A. Milne-Edwards, 1883) and Glyphocrangon alispina Chace 1939, and 21 were previously reported: A total of 80 species of deep-sea decapod shrimp had been reported in Venezuelan territorial waters, representing 12 families and 42 genera. The Acanthephyridae family contributed the highest number of species (14) followed by Sergestidae (9).

Characterization of the Mitochondrial Genome of Cambaroides schrenckii (Astacidea: Cambaridae) and Its Phylogenetic Implications

BACKGROUND

Cambaroides schrenckii is an endangered freshwater crayfish in China, belonging to the genus Cambaroides, that can act as a complementary host for paragonimus. The objective of this study was to examine the complete mitochondrial genome characteristics and their evolutionary relationships within the Astacidea.

METHODS

The analysis of gene rearrangements and evolutionary relationships was conducted through the sequencing of the mitochondrial genome of C. schrenckii.

RESULTS

C. schrenckii mitochondrial genome length was 15,572, comprising thirteen PCGs, two rRNAs, 22 tRNAs, and one d-loop region of C. schrenckii. The mitochondrial genome of C. schrenckii exhibits an A + T content of 69.61% and a G + C content of 30.39%. Among the thirteen PCGs, cytb, nad3, and nad6 have a start codon of ATT, while the other ten PCGs have ATC, ATA, and ATG start codons. All 22 tRNA genes displayed a typical cloverleaf secondary structure. Gene rearrangement analysis showed that seven gene arrangements were identified based on PCGs in the infraorder Astacidea, with type I being the most common.

CONCLUSIONS

The relationship between the American Cambaridae is closer to Astacidae than the Asian Cambaridae. The present study provides a theoretical basis for further discussions of developmental relationships in the infraorder Astacidea.

A new southern Atlantic cryptic marine shrimp species of Acetes (Decapoda, Sergestidae)

A recently published molecular phylogenetic analysis, focusing on selected Western Atlantic subspecies of Acetesamericanus Ortmann, 1893 and allies, was inconclusive about relationships among these members. This previous study found three groups that split into two distinct lineages: Acetesamericanus (Brazil 1) (= A.americanus sensu stricto) and Acetesamericanus (Brazil 2) + A.americanus (USA). Combined morphometry and molecular analyses applied to members of the group Acetesamericanus (Brazil 2) revealed a new unidentified species genetically related to the A.americanus representatives. However, at that time, no conclusive morphological characters were found to identify it. In the present study, following an in-depth morphological analysis of specimens from the three groups, including data on the type series and consideration of the subtle distinctions of members of each lineage, morphological features of the reproductive structures (petasma and genital sternite) were found to characterize the new species, which is formally described and named herein.

Genetic variation and cryptic lineage among the sergestid shrimp Acetes americanus (Decapoda)

The taxonomic status of the sergestid shrimp, Acetes americanus, has been questioned for several decades. No specific study has been performed thus far to resolve the incongruences. This species has a wide geographical range in the western Atlantic and is represented by two formally accepted subspecies: Acetes americanus carolinae, distributed in North America, and Acetes americanus americanus, present in South America. However, there are regions where the coexistence of both subspecies has been reported, such as Central America. This study aimed to genetically compare specimens of A. a. americanus collected in South America with A. a. carolinae sampled in North America to check for possible differences and the existence of more than one subspecies of A. americanus on the Brazilian coast. Based on the sequences of two informative markers, the cytochrome oxidase I region (COI) and 16S rRNA, phylogenetic reconstruction demonstrated well-defined clades with high support values, reinforcing the idea that A. a. americanus is genetically different from A. a. carolinae. Our hypothesis was corroborated as the specimens collected in Brazil were divided into two distinct lineages: the first composed of A. a. americanus sensu stricto (Brazil 1) and the second by Acetes americanus (Brazil 2). The three groups evidenced in the haplotype network were the same as those observed in the phylogenetic tree. The morphometric character (height/length of the thelycum) was effective in distinguishing A. a. Brazil 1 from A. a. carolinae. However, more detailed and conclusive studies comprising other characteristics to propose and describe a possible new entity are necessary. To the best of our knowledge, for the first time, the results of this study provide some insights into the taxonomic status of the sergestid shrimp A. americanus in the western Atlantic.

Early larval development of the rock shrimps Sicyonia dorsalis Kingsley, 1878 and S. typica (Boeck, 1864) (Dendrobranchiata) with remarks of larval morphology of Sicyoniidae Ortmann, 1898

Abstract The aim of this study was to describe and illustrate the early larval stages, i.e., the complete naupliar development and the first protozoea (PZI) of Sicyonia dorsalis and S. typica obtained under laboratory conditions. We also provide remarks from a comparative analysis of the morphology of these stages among representatives of the genus and furnish morphological characteristics to distinguish them from another penaeoidean in the plankton. Our results indicate that the naupliar development of Sicyonia is composed of five stages (NI to NV). No differences were found in the morphology of the naupliar and PZI stages of the two studied species, even though they are considered phylogenetically distant into the genus. We suspect that morphological differences arise later during ontogenetic development. The comparisons with larval descriptions of congeners revealed that naupliar stages and PZI were very similar, nevertheless, some morphological differences were observed. As illustrated here, there is a clear need of new descriptions of the studied group and generalizations and conclusions of larval morphology patterns at this point need to be made with caution, because data of a still insufficient number of species is available.