Abstract Fiddler crabs are important components of intertidal benthic macrofauna in estuarine habitats. However, these invertebrates often inhabit areas under anthropogenic-driven changes. In this study, we evaluated the habitat quality and the population biology of the fiddler crab Uca maracoani (Latreille, 1802) in a mangrove area under anthropogenic influence, on the southern coast of São Paulo state, Brazil. Sediment samples for ecotoxicological analyses and data on the population biology of U. maracoani were collected monthly between October 2008 and October 2009. Contamination was observed in sediment samples from all months, indicating that benthic organisms inhabiting the study area are continuously exposed to toxicity. The sex ratio did not deviate from 1:1 for the whole population of U. maracoani, within any given month (except in October 2008, when males outnumbered females). Adult males and females showed a similar size, while juvenile females were larger than juvenile males, probably reflecting that females attained sexual maturity at a larger size than males. For both juvenile and adult stages, the major cheliped propodus length and height in males and the abdomen width in females showed positive allometry. The size-frequency distribution of the studied population varied from unimodal to bimodal. Juveniles were recorded in all months, suggesting the studied population has continuous recruitment. In contrast, ovigerous females were not found in the study area for several months. Although U. maracoani is continuously exposed to contamination present in the sediment, it presents a well-established population and seems to persist in the study area.

Abstract The population structure and growth of two populations (Arraial and Capivari rivers) of Aegla schmitti was evaluated. The following parameters were determined: size, age structure, sex ratio, recruitment period, and sampling method selectivity (traps and handnet). There was variation between males and females. The carapace length size class distribution was unimodal in the Arraial River, and polymodal in the Capivari River. The sampling method influenced the proportion of demographic categories. The recruitment occurred mostly between October and December. The growth curves for the Arraial and Capivari rivers, respectively, were Ct= 26,50[1- e -0,004(t+53,36)] and Ct= 34,79[1- e -0,0024(t+122,34)] for males, and Ct= 23,07[1- e -0.0027(t+23,18)] and Ct= 25.52[1- e -0,0033(t+19,51)] for females. The maximum CL estimated for males and females were 26.50 and 23.07mm for the Arraial River, and 34.79 and 25.52mm for the Capivari River. Longevity was estimated in 2 years for females of both populations, and 2.5 and 3 years for males of the Arraial and Capivari rivers, respectively. The results allow for the characterization of the growth patterns of A. schmitti in two hydrographic basins, providing information for the species’ preservation and also demonstrating the selectivity of the different sampling methods used for aeglids.

ABSTRACT A study on relative growth, sexual dimorphism and ontogenetic trajectory was carried out in a population of the aeglidAegla marginata coming from Barrinha River, Iguape River Basin, Tunas do Paraná, Paraná State, Brazil. The size the of morphological sexual maturity was estimated for males and females. The analysis of sexual dimorphism and ontogenetic trajectory were performed using geometric morphometric technique. Males reach maturity with 10.58 mm of carapace length (CL) and females with 10.38 mm CL. Sexual size dimorphism was only visible among adults, with males reaching larger sizes. This is probably related to the reproductive strategy of males. However, sexual shape dimorphism was found for both juveniles and adults: the posterior region of the carapace was wider in females. As the contrast of this feature was stronger in adults, it can be considered that large abdomen is advantageous for egg incubation. The allometric trajectories of juveniles presented similar directions, becoming divergent during the adult phase. The shape variation inA. marginataoccurred gradually throughout its development, with no abrupt transformation upon reaching sexual maturity. The reproductive adaptation is the main reason for the morphological variation within populations ofA. marginata.

RESUMO Um estudo sobre o dimorfismo sexual no caranguejo Hepatus pudibundus (Herbst, 1785) foi realizado utilizando morfometria geométrica. A carapaça de 28 machos e 30 fêmeas e o própodo dos quelípodos direito e esquerdo de 22 machos e 26 fêmeas foram analisados. Foram estabelecidos 13 marcos anatômicos bidimensionais na carapaça e 10 no própodo para ambos os sexos. Uma Análise Generalizada de Procrustes baseada na configuração dos marcos anatômicos foi utilizada para separar os componentes de tamanho e de forma. Um Teste-t de Student foi utilizada para determinar a significância estatística do dimorfismo sexual da carapaça e do própodo dos quelípodos. A variação na forma das estruturas foi avaliada através de uma Análise de Função Discriminante. Houve dimorfismo sexual na forma e no tamanho das estruturas analisadas. Machos mostraram dimensões menores do que fêmeas. A carapaça das fêmeas foi mais larga na região posterior do que em machos, indicando uma ampliação da área para acomodação da massa de ovos. O dedo fixo do própodo dos quelípodos das fêmeas está mais voltado para a parte posterior e pode facilitar a limpeza dos ovos fixados na câmara abdominal. Nossos resultados trazem novas informações sobre o desenvolvimento de caracteres sexuais secundários e as suas consequências sobre a forma da carapaça e o própodo dos quelípodos em machos e fêmeas de H. pudibundus.

ABSTRACT A study on sexual dimorphism in Hepatus pudibundus (Herbst, 1785) was performed using geometric morphometrics. The carapace of 28 males and 30 females and the left and right cheliped propodus of 22 males and 26 females were analyzed. Thirteen landmarks were established in the carapace and 10 in the cheliped propodus. A Generalized Procrustes Analysis based on landmark configurations was used to separate the components of size and shape. A Student t-test was used to determine the statistically significant sexual dimorphism of the carapace and the cheliped propodus. The variation in the shape of the structures was evaluated with a discriminant analysis. There was sexual dimorphism in the analyzed structures. Males were smaller than females. The carapace of females was larger in the posterior region than in males, indicating an expansion of the area for accommodation of the egg mass. The fixed finger of the cheliped propodus of females is more posteriorly arched that can be used to facilitate the cleaning of eggs laid in the abdominal chamber. Our results provide new information about the development of sexual secondary characters and their effects on the shape of the carapace and the cheliped propodus in males and females of H. pudibundus.