The influence of environmental variables in the reproductive performance of Macrobrachium amazonicum (Heller, 1862) (Caridea: Palaemonidae) females in a continental population.

Macrobrachium amazonicum is a commercially important freshwater prawn with a high degree of reproductive plasticity. The species is classified into two groups: coastal populations, with larger individuals exhibiting high fecundity and needing brackish water for larval development; and continental populations, with smaller specimens exhibiting low fecundities and completing metamorphosis in freshwater. The objective of this study was to investigate the influence of environmental factors in the fecundity, egg size and volume, and reproductive output in females of M. amazonicum from a continental population during a two-year period. We also compared our results with those obtained for other continental and coastal populations. Reproductive parameters differed markedly between continental and coastal populations in most cases. The continental population studied here, however, exhibited reproductive characteristics similar to those of coastal populations. The present study found a correlation between the reproductive parameters and the environmental variables analyzed. This result corroborates the hypothesis that wide variation in reproductive parameters in the geographical distribution of M. amazonicum is related to the environmental characteristics in which populations are inserted. We suggest that further studies could investigate the potential of continental populations for aquaculture, which could significantly reduce production costs.

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.

New Insights into the Life-history Traits of the Night Shrimp Processa hemphilli (Caridea: Processidae) in the Western Atlantic.

We analyzed sexual dimorphism, sex ratio, relative growth, morphological sexual maturity, fecundity, embryo volume, and reproductive output of a population of the night shrimp Processa hemphilli from the Southeast coast of Brazil. Sampling was seasonally conducted, from June 2016 to April 2019 in Ubatuba, São Paulo. Our results showed the presence of sexual dimorphism in the body size, with females being larger than males. In addition, there was no difference in the overall sex ratio. However, it was possible to observe a skewed sex ratio to males in the smaller size classes, whereas females were more abundant in the larger size classes. The estimated carapace length at the onset of morphological sexual maturity of females and males was 3.6 mm and 3.2 mm, respectively. The mean fecundity of females was 285 ± 142 embryos (mean ± SD) embryos and was positively correlated with the carapace length. The embryo volume differed between the developmental stages with a constant increase in volume throughout the development between stages I and III. The mean reproductive output of females was 52.4%. Our results suggest that P. hemphilli have a pure search mating system, show sex allocation in the growth of body structures, and that females have high reproductive investment. All of these results represent the first insights into the life-history traits of the species in the western Atlantic and contribute to the knowledge about processid species.

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

This checklist is the fifth and last compilation on the decapod crustaceans reported to So Paulo (Brazil) coastal area, resulting from long-term multidisciplinary projects, which combined morphological analyses and molecular techniques. The current research includes 75 decapod species, herein referred as shrimps/lobsters-like (shrimps, ghost-shrimps, lobsters, and related groups), reported to So Paulo coastal area. These species occur in marine, estuarine, and amphidromous habitats and are classified into 21 families as follow: Aristeidae (2 spp., 2 genera), Atyidae (4 spp., 2 genera), Axianassidae (1 sp., 1 genus), Callianassidae (1 sp., 1 genus), Callichiridae (6 spp., 4 genera), Crangonidae (1 sp., 1 genus), Glyphocrangonidae (1 sp., 1 genus), Luciferidae (2 spp., 2 genera), Nephropidae (4 spp., 2 genera), Palaemonidae (15 spp., 9 genera), Palinuridae (2 spp., 1 genus), Pandalidae (1 sp., 1 genus), Pasiphaeidae (1 sp., 1 genus), Penaeidae (10 spp., 6 genera), Sergestidae (3 spp., 3 genera), Sicyoniidae (4 spp., 1 genus), Scyllaridae (5 spp., 3 genera), Solenoceridae (4 spp., 3 genera), Stenopodidae (2 spp., 1 genus), and Upogebiidae (6 spp., 1 genus). We generated new sequences of cytochrome oxidase subunit I (barcode region) and 16S genes (51 and 54, respectively) of 54 species. Our examination concluded that 75 shrimps/lobsters-like species are reported to the So Paulo coast. We excluded Leander tenuicornis (Palaemonidae), Penaeus setiferus (Penaeidae), Philocheras gorei (Crangonidae), and Rhynchocinetes typus (Rhynchocinetidae) from this list.

Evaluating food web interactions among microcrustaceans and insect in a tropical shallow lake using DNA-based protocol.

We developed species-specific primers of five microcrustacean preys, Ceriodaphnia richardi, Diaphanosoma cf. brevireme, Daphnia gessneri, Simocephalus serrulatus, Thermocyclops decipiens and Mesocyclops sp., to analyze food-web interactions involving their two insect predators Rheumatobates crassifemur and Martarega uruguayensis distributed in a tropical shallow lake. We designed internal primers of the COI gene (177-282 bp), and tested them, by means of PCR, for specificity and sensitivity. In our tests for specificity, all primers successfully amplified the DNA target but were species-specific failing to amplify the biomarker from any of the other species tested, even in a mixed DNA sample, including predators' DNA. In tests for sensitivity, primers successfully amplified zooplankton biomarkers from low concentration of DNA extractions and also from digestive tract of predators, even after many hours of ingestion. This technique provides a framework as an efficient tool for evaluation of food-web research in natural aquatic environments, where it is impossible to observe if predation occurs. Furthermore, this technique provides an effective solution for the identification of zooplankton species from the predator's digestive tract, where morphological identification alone is sometimes difficult because predators do not consume the prey but feeds using extra-oral digestion, such is the case of heteropterans.

Validation of Xiphopenaeus dincao Carvalho-Batista, Terossi, Zara, Mantelatto amp; Costa and Xiphopenaeus baueri Carvalho-Batista, Terossi, Zara, Mantelatto amp; Costa (Decapoda: Penaeidae) from western Atlantic.

Two species of Penaeidae shrimp from western Atlantic were described by Carvalho-Batista et al. (2019) as Xiphopenaeus dincao and Xiphopenaeus baueri. The descriptions and figures presented by Carvalho-Batista et al. (2019) and the posterior author's correction (Carvalho-Batista et al., 2020) characterize the species. However, the journal issue in which the description was published is online only, and the article with the new names did not include a Zoobank registration number (LSID), required for validation of new names in electronic-only publications (ICZN 2012). Thus, the names Xiphopenaeus dincao and Xiphopenaeus baueri, as published in Scientific Reports 9: 15281, is not available according the International Code of Zoological Nomenclature (ICZN 1999, 2012). Therefore, the present note serves to validate the names Xiphopenaeus dincao and Xiphopenaeus baueri by fulfilling ICZN conditions for nomenclatural availability. Type specimens of both species are deposited in Museu de Zoologia da Universidade de São Paulo (MZUSP), São Paulo, Brazil.

Author Correction: A multigene and morphological analysis expands the diversity of the seabod shrimp Xiphopenaeus Smith, 1869 (Decapoda: Penaeidae), with descriptions of two new species.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

A multigene and morphological analysis expands the diversity of the seabod shrimp Xiphopenaeus Smith, 1869 (Decapoda: Penaeidae), with descriptions of two new species.

After being stable for nearly a century, the taxonomic history of the genus Xiphopenaeus has been marked by many changes in the last three decades. The taxonomic status of the Atlantic species has a low resolution, and many species are still undefined and grouped as cryptic species. Here we employed an integrative approach to define the species of Xiphopenaeus and the morphological characters needed to differentiate them. We combined the analyses of two molecular markers (COI and 16 S rDNA), scanning electron microscopy and light microscopy. Based on specimens from 17 localities from the Atlantic and Pacific oceans, we detected five divergent genetic groups, three in the Atlantic (A1, A2, A3) and two in the Pacific (P1, P2). Male secondary sexual characters were able to differentiate four out of the five genetic groups. Group A1 corresponds to X. kroyeri, and A2 and A3 correspond to new species. We redescribed the genus and two new species are described and illustrated: Xiphopenaeus dincao nov. sp. (A2) and Xiphopenaeus baueri nov. sp. (A3). Since the holotype of X. riveti was missing and the specimen analysed from group P2 was a female, the status of the species of Xiphopenaeus from the Pacific remains unresolved.

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

Artemesialonginaris 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 Artemesialonginaris 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.