Abstract The morphology of the first zoeal stage of Pilumnus vinaceus is described and compared with the zoea I of Pilumnus all species in the literature. Two ovigerous females of P. vinaceus were maintained in the aquarium facilities until the larvae hatch. The larvae of each ovigerous female were dissected using a stereoscopic microscope. The zoea I of P. vinaceus has common characteristics among the Pilumnidae as: [1] antenna of type 2; [2] maxilliped 1 with 2+2+3+3 setae on the basis and with 3,2,1,2,5 setae in the endopod; [3] maxilliped 2 with 1+1+1+1 setae on the basis and 1,1,6 setae on the endopod; [4] telson with furcal rami armed with dorsal and lateral spines. Considering the species of Pilumnus that occur in the western Atlantic, it becomes possible to identify P. vinaceus zoea I by means of the verification of the following characteristics: [1] pleonites with mediolateral processes; [2] number of setae on the antennule. It is however, important to consider that there is still a great deficit in the knowledge about the morphology of the larval forms of the species assigned to Pilumnus and we argue in favor of new descriptions to build a more robust dataset on zoeal morphology characters and use it in a phylogenetic context on the genus.

Abstract The objective of this study is to report the first occurrences of three species from the genus Lysmata Risso, 1816 in an area of the Queimada Grande Island (QGI), a conservation unit on the southern coast of São Paulo, southeastern Brazil. The specimens were sampled manually in August 2018 from a small rocky formation from the QGI region. The species Lysmata bahia Rhyne and Lin, 2006, Lysmata uncicornis Holthuis and Maruin, 1952, and Lysmata vittata (Stimpson, 1860) are reported, of which the last two are not native to the Western Atlantic waters. The present study reports L. uncicornis for the first time on the coast of São Paulo State. The records informed herein not only provide more information about biodiversity, but can also help in the development of management plans and conservation.

Abstract Considering the environmental impacts to rivers caused by the exploitation of water resources and the consequences of these impacts upon fauna, the objective of this study was to evaluate the population biology of the shrimp Atya scabra (Leach, 1816) in the final stretch of the major river of South America. This species was assessed as “Near Threatened” in the red book of Brazilian crustaceans. Specimens were sampled monthly from February 2015 to January 2016 in a region of the lower São Francisco River, Brazil. A total of 233 individuals of A. scabra were collected, including 120 males and 113 females (71 non-ovigerous and 42 ovigerous). Atya scabra abundance was higher when water flow values increased. A decrease in abundance was observed over the one year of sampling, indicating a decline of about 90 % in this population in this region of the São Francisco River. We suggest that this decline was caused by the reduction of water flow in the São Francisco River, due to a policy that authorized retaining more water behind dams and releasing less water into the river in April and June 2015. In light of this, other studies should monitor the population dynamics of this species, while legislative actions are also needed to protect this fragile ecosystem.

Abstract The present study aims to describe the population structure of the freshwater prawn Macrobrachium brasiliense and to analyze whether it varies seasonally, with emphasis on abundance variation by demographic category, sex ratio, size, and morphotypes, in addition to analyzing the recruitment period and its relationship with rainfall. The collections of M. brasiliense were carried out in a Cerrado region, in the southeastern region of Brazil. The population structure was analyzed according to the size, sex, and life stage. The density of morphotypes was calculated by the proportion of each morphotype in the population. Male and female prawns were more abundant in the largest and smallest size classes, respectively. The juvenile morphotype was the most abundant among males (45.9 %), while the “Mirim” and “Açu” morphotypes occurred in a similar proportion (27.87 % and 26.23 %, respectively). The population structure varied significantly between seasons (dry and rainy). A relationship of juvenile abundance with rainfall was recorded. The recruitment period was observed between the end of the rainy season and the beginning of the dry season, while adults were more abundant at the end of the dry season and the beginning of the rainy season. The information in this study contributes to the knowledge of the influence of seasonality and rainfall on populations of aquatic organisms in the Cerrado region, such as the prawn M. brasiliense. Rainfall seasonality affects the population structure of these organisms between seasons, possibly due to the top-down and bottom-up effects caused by different rates of nutrient input in such aquatic systems.

ABSTRACT Hermit crabs are common and abundant members of the intertidal community and in sublittoral bottoms, where they play a fundamental role in the trophic chain. This study aimed to determine the composition of the hermit crab fauna, to quantify the density in the natural environment, and to register shells use by main species from subtidal boulder fields, in an island off the southeastern Brazilian coast. Monthly samples were taken from March 2010 to February 2011 on boulder fields on Couves Island, Ubatuba, Brazil, during scuba diving daytime sessions. Three hundred and eighty-three crabs were collected by hand, in a quadrat of 20 m2 belonging to five species: Calcinus tibicen, Dardanus venosus, Pagurus brevidactylus, Paguristes tortugae, and Petrochirus diogenes. The highest densities were recorded for P. brevidactylus and P. tortugae. Hermit crabs occupied shells of 15 gastropod species. Cerithium atratum, Gemophos auritulus, and Morula nodulosa comprised more than 80% of the occupation. The heterogeneity of boulder fields of Couves Island, composed almost entirely of small refuges and crevices, favors the exploration of hermit crab species recorded here, which are characterized by small size. These results, combined with the findings of further studies, can contribute to the development of effective monitoring programs for decapod crustacean species.

Abstract Mussel farms are one of the most important modalities of aquaculture and constitute almost 80% of the total bivalve production in Brazil, representing about 5% of the national production. Brachyuran crabs are common inhabitants of these environments and represent an important link in coastal marine food chains. The aim of this investigation is to describe the population structure of Panopeus austrobesus Williams, 1983 in a Perna perna (Linnaeus, 1758) farm located at the southeastern Brazilian coast. The samplings were carried out in the northeastern coast of São Paulo State. From May 2002 to April 2003, one mussel net was recovered monthly, and all individuals of P. austrobesus were collected. Population size-frequency analysis indicated a unimodal and non-normal distribution. Males were significantly larger than females, and the overall sex ratio significantly skewed from 1:1, female-biased. Recruitment occurred during the entire period, and ovigerous females were found in 11 months. The onset of sexual maturity was estimated around 5 mm cephalothorax width. Mussel farms represent an anthropogenic intervention in the sea landscape, causing environmental changes. However, these structures must allow species introduction, increasing their ecological and geographical distribution, and provide available space and food to establish new populations. This is particularly important for species with small populations, such as P. austrobesus. The results of this study attest the environmental counterpart role of the mussel farms. Once they can support populations, they may also help to reintroduce them into the area and could therefore be used in a consortium generating economic profits and acting as bioremediation tool, assuring the maintenance of the genetic patrimony.

ABSTRACT The morphology of the first zoeal stage of Domecia acanthophora (Desbonne, in Desbonne & Schramm, 1867) was described from laboratory-hatched material obtained from ovigerous females collected at Vitória Island on the southeastern Brazilian coast. We compared the larval morphology (zoea I) of fourteen species of the superfamily Trapezioidea, which Domecia glabra Alcock, 1899 is the only congeneric representative of the species described in this study. The morphological characteristics of the first zoea that distinguish D. acanthophora from D. glabra are: three aesthetascs on the exopod antennule; three pairs of lateral spines on carapace; bilobed basial endite of maxilla, with four plumodenticulate setae on each lobe; and telson furcae distally spinulated. It also provides information that may enhance some phylogenetic hypotheses within Trapezioidea crabs.

Abstract Information concerning the morphology of Dendrocephalus brasiliensis Pesta, 1921 is currently fragmented. This study reviewed the morphological structures described previously and new features (e.g., antenna-like structures and gonopod). We review the distribution of this species and also expand the geographic distribution of D. brasiliensis in the state of Alagoas. The specimens were obtained from fish-breeding tanks in Porto Real do Colégio, Alagoas, Brazil, in November 2012. Several morphological structures of D. brasiliensis are described in greater detail, including all branches and sub-branches from the frontal appendage and thoracopods from one population and compared to other species.

ABSTRACTThis contribution reviews the morphology and the main diagnostic characters of the peppermint shrimp Lysmata ankeri. Individuals were sampled by scuba divers from August 2008 to June 2013 on the subtidal rocky bottom at Couves Island, on the coast of São Paulo State, Brazil. In the laboratory, the individuals were analyzed morphologically, with emphasis on the characters used in the diagnosis of the species; measured as carapace length (CL); and photographed. Seventeen individuals of L. ankeri were analyzed with an average size of 6.9 ± 2.0 mm CL. From the morphological analysis the following variations of the diagnosis were observed: five teeth on the dorsal margin of the rostrum, in the diagnosis this was 6-8; five spines on the flexor margin of the dactyli of pereiopods 2-4, in the diagnosis this was 3-4. The records of this study extend the knowledge of the variation of some morphological characteristics for this species, resulting in an overlap among the species of the Lysmata wurdemanni complex.

OBJETIVO: A biologia populacional do camarão de água doce Macrobrachium jelskii foi investigada, com ênfase na distribuição de frequência em classes de tamanho, razão sexual, período reprodutivo e recrutamento juvenil. Além disso, a abundância dos indivíduos foi correlacionada com os fatores abióticos. MÉTODOS: Amostras foram coletadas mensalmente de julho de 2005 a junho de 2007, às margens do Rio Grande, região de Planura, estado de Minas Gerais, Brasil (20º 09' S e 48º 40' W), usando uma rede de arrasto (1.0 mm tamanho da malha e 2.0 × 0.5 m de largura). O equipamento foi arrastado por duas pessoas às margens da vegetação do rio por 100 metros de distância, percorridos por uma hora. Em laboratório, os espécimes foram identificados, mensurados e sexados. RESULTADOS: Um total de 2,789 espécimes foi analisado, no qual correspondem a 1,126 machos (549 jovens e 577 adultos) e 1,663 fêmeas (1,093 jovens, 423 adultos não ovígeras e 147 ovígeras). A razão sexual diferiu significativamente a favor de fêmeas de M. jelskii (1:1.48; χ² = 103.95; p < 0.0001). A média de tamanho do comprimento da carapaça (CL) das fêmeas (6.32 ± 1.84 mm CL) foi estatisticamente maior do que dos machos (5.50 ± 1.07 mm CL) (p < 0.001). A distribuição de freqüência em classes de tamanho dos espécimes revela um padrão de distribuição unimodal e não normal para machos e fêmeas (W = 0.945; p < 0.01). Não foi observada relação entre a abundância de M. jelskii e as variáveis ambientais (p = 0.799). CONCLUSÃO: A presença de fêmeas ovígeras e jovens na população sugere um padrão de reprodução e recrutamento contínuos para M. jelskii na região de Planura.

AIM: The population biology of the freshwater shrimp Macrobrachium jelskii was investigated here emphasizing the length-frequency distribution, sex ratio, reproductive period and juvenile recruitment. In addition, the abundance of individuals was correlated with the abiotic factors. METHODS: Samples were collected on a monthly basis from July 2005 to June 2007 along the river margin in shallow water of Grande River, at Planura region, State of Minas Gerais, Brazil (20º 09' S and 48º 40' W), using a trawl net (1.0 mm mesh size, and 2.0 m × 0.5 m wide). The fishing gear was handled by two people along the marginal vegetation of the Grande River in a course of 100 m, covered for one hour. In the laboratory, the specimens were identified, measured and sexed. RESULTS: A total of 2,789 specimens was analyzed, which corresponded to 1,126 males (549 juveniles and 577 adults) and 1,663 females (1,093 juveniles, 423 adults non-ovigerous and 147 ovigerous). The sex ratio differed significantly in favor of the females of M. jelskii (1:1.48; χ² = 103.95; p < 0.0001). The mean size of carapace length (CL) of females (6.32 ± 1.84 mm CL) was statistically higher than of males (5.50 ± 1.07 mm CL) (p < 0.001). The length-frequency distribution of the specimens revealed an unimodal pattern and non-normal distribution for males and females (W = 0.945; p < 0.01). No significant relationship between the abundance of M. jelskii and the environmental variables was observed (p = 0.799). CONCLUSION: The presence of ovigerous females and juveniles in the population suggests a continuous reproduction pattern and recruitment for M. jelskii at Planura region.

The geographical distribution of marine organisms, as a result of complex natural processes through geological time, has been changed, sometimes drastically, by species introductions. Instances of species introduction have been recorded worldwide, and the Brazilian coast is no exception. The present review provides an update of the geographical distribution of members of the brachyuran subfamily Mithracinae along the Brazilian coast. Of the 30 species of this subfamily recorded from Brazilian waters, the known geographical limits of more than 17 have been extended in recent decades. The records compiled here demonstrate the great importance of the Amazon River outflow on the geographical distribution of members of Mithracinae, acting as a biogeographical barrier for some species.