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 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.

Estudou-se uma população do caranguejo Sesarma rectum Randall, 1840 que está sob a influência direta do impacto humano. Coletas mensais (CPUE, duas pessoas durante 30 min) foram realizadas de agosto de 2001 a julho de 2002 numa área lodosa, localizada na cidade de Paraty, Estado do Rio de Janeiro (23º13'S, 44º42'W). No laboratório, os espécimes foram classificados quanto ao sexo e posteriormente medidos com um paquímetro (0,01 mm). O tamanho do início da maturidade sexual foi obtido por meio de diferentes técnicas: no caso dos machos, utilizaram-se técnicas alométrica e a análise macroscópica das gônadas, enquanto para as fêmeas, o tamanho da menor fêmea ovígera também foi considerado. A estrutura da população foi avaliada pela análise da variação das modas da distribuição de freqüência por classes de tamanho. A fecundidade foi obtida por meio de subamostragens das massas de ovos. Para os machos, a análise macroscópica das gônadas revelou valores da largura da carapaça maiores que os obtidos com as análises morfométricas. Machos maiores que 18,5 mm de largura da carapaça foram considerados maduros. Para as fêmeas, o tamanho da maturidade foi 17,4 mm de LC. Apesar do impacto humano sobre o ecossistema, a população apresenta-se estável, o que é indicado pela presença de uma única moda na distribuição de freqüência de tamanho. Uma segunda moda aparece somente em alguns meses e, provavelmente, está relacionada à entrada de juvenis na população. A razão sexual da população é próxima de 1:1 até os caranguejos alcançarem o tamanho em torno de 28 mm de LC. A seguir o número de machos ultrapassa o de fêmeas. Comparando a fecundidade da presente população com a estudada previamente em Ubatuba, verificaram-se diferenças no número de ovos. A fecundidade da população de Paraty foi significativamente menor do que a de Ubatuba. Isto provavelmente está relacionado à escassez de recursos alimentares em Paraty, uma vez que não se encontram plantas vasculares naquele local. O processo reprodutivo contínuo, como também o recrutamento juvenil sugere que a espécie está apta a viver nesta área mesmo sob impacto humano. A capacidade de obtenção de nutrientes a partir de diferentes tipos de alimentos é provavelmente uma característica que possibilita S. rectum ocupar um ecossistema impactado.

A population of Sesarma rectum Randall, 1840 under the influence of human impact was studied. Monthly sampling (CPUE, two people during 30 min) took place from August/2001 to July/2002 at an impacted muddy flat in Paraty city, State of Rio de Janeiro (23º13'S, 44º42'W). At the laboratory, specimens were classified by sex and measured with a vernier caliper (0.01 mm). The size at the beginning of the sexual maturity was obtained by means of different techniques: in the case of males it was used the allometric procedure and the macroscopic analysis of gonads wile for females, the size of the smallest ovigerous female was also considered. The population structure was evaluated by means the analysis of the variations in the modes of the size frequency distribution. The fecundity was assessed using sub samples of the egg mass. For males, the macroscopic analyses of gonads revealed larger values of carapace width than those obtained with morphometric analysis. Males larger than 18.5 mm of carapace width can be considered as mature. For females, such size was 17.4 mm CW. Despite of the human impact in the habitat, the population presented to be stable, as indicated by a single mode on the size frequency distribution. The second mode that appeared in some months is probably related to the entrance of juveniles in the population. The sex ratio of this population is closely approximating to 1:1 until crabs reach a carapace width of about 28 mm; after that, males outnumbered females. Comparing the fecundity of the present population with a previous study from Ubatuba, it can be verified a difference in the number of eggs. The fecundity of Paraty's population is significantly lower than the Ubatuba's population. This is probably related to the scarcity of food resource in Paraty, once no vascular plant can be found in that place. The continuity of reproductive processes and the juvenile recruitment suggest this species is able to live in the area with human impact. The ability to obtaining nutrients from different source of food is probably a feature that allows S. rectum to occupy such impacted ecosystem.