No abstract

This study records, for the first time, the occurrence of all four male morphotypes in a population of Macrobrachium amazonicum from a continental environment, with an entirely freshwater life cycle. The specimens studied came from the Tietê River, state of São Paulo, Brazil, and were collected in a lotic environment downstream from Ibitinga Dam. This population was compared with other continental populations, including a population from the dam itself, collected in a previous study. Four samples of 30 minutes were taken monthly, using a trap, from January to April 2011. Each male specimen was measured with respect to seven body dimensions as follows: carapace length (CL), right cheliped length (RCL), dactyl length (DCL), propodus length (PPL), carpus length (CRL), merus length (ML) and ischium length (IL). The relative growth was analyzed based on the change in growth patterns of certain body parts in relation to the independent variable CL. The four male morphotypes proposed for the species were found using morphological and morphometric analyses. Different biological characteristics were found between the populations studied. The male population of the lake of Ibitinga and from Pantanal presented mean sizes and number of morphotypes lower than the population studied here. These differences seem to be closely related to ecological characteristics of the environments inhabited by these populations. Our results supported the hypothesis that coastal and continental populations of M. amazonicum belong to the same species.Keywords: freshwater prawn, allometry, Tietê River, Amazon River Prawn, morphotype characterization. Ocorrência de morfotipos em machos de Macrobrachium amazonicum(Caridea, Palaemonidae) em uma população com ciclo de vida completamente dulcícola ResumoEste estudo registra, pela primeira vez, a ocorrência dos quatro morfotipos de Macrobrachium amazonicum em uma população continental com ciclo de vida totalmente dulcícola. Os camarões são provenientes do Rio Tietê, estado de São Paulo, Brasil, e foram coletados em um ambiente lótico abaixo da Barragem de Ibitinga. Essa população foi comparada com outras populações provenientes de ambientes continentais, incluindo a de um estudo anterior na represa da barragem de Ibitinga. Quatro amostras de 30 minutos foram realizadas mensalmente, utilizando armadilhas, de janeiro a abril de 2011. Cada indivíduo macho foi mensurado em relação a sete dimensões corporais, sendo elas: comprimento da carapaça (CL), comprimento total do quelípodo direito (RCL), comprimento do dáctilo (DCL), comprimento do própodo (PPL), comprimento do carpo (CRL), comprimento do mero (ML) e comprimento do ísquio (IL). O crescimento relativo foi analisado de acordo com as mudanças nas taxas de crescimento de determinadas partes do corpo em relação à variável independente CL. Os quatro morfotipos descritos para a espécie foram encontrados, utilizando análises morfológicas e morfométricas. Diferentes características biológicas foram encontradas entre a população estudada e as demais...

Some crustaceans show variations of their reproductive biology within their geographical distribution, and knowledge about such variations is important for the comprehension of their reproductive adaptations. This study compared two populations of the fiddler crab Uca uruguayensis from two locations on the south-western Atlantic coast: Ubatuba Bay, São Paulo, Brazil and Samborombón Bay, Buenos Aires, Argentina. The population features analysed were the body size variation (carapace width ¼ CW) and the size at the onset of sexual maturity (SOM) in order to test the hypothesis that the size at SOM, should be the same in relative terms (RSOM), independently of the latitudinal position. In the Brazilian population the CW ranged from 4.18 to 11.60 mm for males and 3.90 to 9.80 mm for females, and in the Argentinean population from 3.60 to 14.10 mm for males and 2.85 to 12.00 mm for females. In the Brazilian population the SOM was 7.1 (RSOM ¼ 0.58) and 5.9 mm CW (RSOM ¼ 0.57) for males and females, respectively, and in the Argentinean population it was 7.0 (RSOM ¼ 0.42) and 6.75 mm CW (RSOM ¼ 0.53) for males and females, respectively. This fact is probably related to a great plasticity in the life history features of Uca uruguayensis under different environmental conditions.

ABSTRACT. 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 (23 º 13'S, 44 º 42'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. KEYWORDS.Sexual maturity, allometric growth, population structure, fecundity. . 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 ...