Abstract The freshwater prawn Macrobrachium jelskii (Miers, 1877) is widely distributed in South America’s lentic and lotic habitats. We studied the population structure and reproductive biology of the species in the municipality of Cruz das Almas, state of Bahia, Brazil, to supply information on this ecologically and economically relevant species. Samples were collected monthly, from February 2013 to January 2014, at Laranjeiras pond. The sex ratio was biased towards females (1.4 females : 1 male). The mean carapace length of females and males was respectively 8.08 ± 1.37 mm and 6.61 ± 1.11 mm. Ovigerous females comprised 22.5% of all sampled females, and their reproductive activity, characterized as seasonal-continuous, was positively correlated with precipitation. The average size of females at the onset of functional maturity was estimated at 6.67 mm CL and the mean fecundity was 25.2 ± 8.9 eggs. Egg size, mass and volume increased significantly during embryonic development. Our data strongly indicate that the reproductive strategy that best fits the species is the “pure search” mating system.

ABSTRACT Macrobrachium amazonicum (Heller, 1862) is a freshwater prawn occurring in rivers and reservoirs of Central and South America. Given its broad geographical distribution, the species shows great intraspecific morphological, reproductive, physiological and ecological plasticity. Furthermore, it also stands out for its economic importance, especially in the states of North (Pará and Amapá) and Northeast Brazil. Despite the wide geographic distribution and economic importance of M. amazonicum, the biology of this species is poorly known, particularly in Northeast Brazil. We analyzed the length-weight relationships and condition factor of males and females of M. amazonicum. Specimens were collected monthly from September 2008 to August 2009 at the Pedra do Cavalo Reservoir, city of Cabaceiras do Paraguaçu, State of Bahia. All specimens were sexed, measured and weighted. After that, length-weight relationships and the allometric (K) and relative (Kr) condition factors were calculated. Altogether 2,974 specimens were analyzed, 334 of which were males (11%) and 2,640 were females (89%). Females were larger and heavier than males. Males and females showed isometric and negative allometric growth, respectively. Monthly variations in the condition factor were similar for both sexes, and correlated strongly with rainfall regime and temperature in the region. Such variations are not correlated with the reproductive cycle of the species, but are probably correlated with food availability and somatic growth.

Freshwater crabs are important elements in the aquatic biota of brooks, rivers, lakes and ponds, from both ecological and the socio-economic aspects. Trichodactylidae comprises 51 endemic species from the Neotropical region. Among all the species of this family, Trichodactylus fluviatilis Latreille, 1828 has the widest geographic distribution throughout Brazil. Despite that, there are few published contributions on the biology of this species. The present study investigated the following aspects of T. fluviatilis: relative growth, mean size at onset of morphometric maturity, sexual dimorphism, laterality and heterochely. Specimens were collected monthly from September 2010 through August 2011, from the Velha Eugênia Brook, municipality of Santa Teresinha, State of Bahia. Carapace width (CW), carapace length (CL), major cheliped length (MaCL) and minor cheliped length (MiCL), major cheliped height (MaCH) and minor cheliped height (MiCH), and width of the fifth abdominal segment (5AB) were measured to evaluate the presence of sexual dimorphism; the major difference between the sexes was in the CW vs. 5AB ratio. Heterochely was observed in males and females,with the right cheliped larger than the left in 89% of males and 81% of females. Crab size at the onset of morphometric maturity (= puberty molt) was estimated based on the ratio between CL, cheliped dimensions, 5AB and CW (independent variable). Females were larger than males when they reached morphometric maturity in all studied relations. We recommend the use of chelipeds and abdominal width relationships to estimate the size at the morphometric maturity in males and females, respectively.

Durante os anos 2000 e 2001 foram realizadas coletas sazonais de crustáceos decápodes em dois pontos de um rio na Estação Ecológica Juréia-Itatins, utilizando-se duas metodologias distintas (peneira e armadilha). Comparando-se ambos os métodos de coleta, foram constatadas diferenças quanto à composição e riqueza da carcinofauna capturada, grau de dominância e equitatividade, bem como tamanho e número de indivíduos coletados. Além disso, as razões sexuais de Macrobrachium acanthurus (Wiegmann, 1836) podem diferir dependendo do método de coleta utilizado. Devido à grande variedade de hábitats e hábitos dos crustáceos, pode-se inferir que, para um levantamento qualitativo e/ou quantitativo eficaz e apurado da comunidade de crustáceos decápodes dulcícolas de um determinado rio, é recomendado o uso de mais de um método de coleta.

Sampling collections were taken quarterly from Fall 2000 to Summer 2001 at Juréia-Itatins Ecological Station using two different sampling methods (hand sieve and traps). Comparing both sampling methods one can verify differences in faunal composition, richness, degree of dominance, evenness and size and number of individuals. Moreover, the sex ratio of Macrobrachium acanthurus (Wiegmann, 1836) may differ according to the sampling method. Decapod crustaceans are known to inhabit a great variety of habitats and niches, therefore to obtain an effective qualitative and/or quantitative sampling, in which the majority of decapod species are collected, the use of more than one sampling method is recommended.

Este trabalho contribui para o conhecimento da riqueza de espécies de crustáceos decápodes do vale do Ribeira de Iguape, região sul do estado de São Paulo. Foram realizadas amostragens em seis Parques Estaduais (Campina do Encantado, Intervales, PETAR, Carlos Botelho, Jacupiranga e Ilha do Cardoso) e na Estação Ecológica Juréia-Itatins, abrangendo grande parte do remanescente de Mata Atlântica da região da bacia do rio Ribeira de Iguape. As coletas foram realizadas sazonalmente durante os anos 2000 e 2001, empregando dois métodos de amostragem (peneira e armadilha com isca). Foram registradas 18 espécies de crustáceos decápodes: Palaemonidae (6), Atyidae (3), Aeglidae (5), Trichodactylidae (3) e Grapsidae (1).

This paper contributes to the knowledge of the species richness and distribution of decapod crustaceans at the Ribeira de Iguape river basin, south of São Paulo State, Brazil. Seven protected areas (E.E. Juréia-Itatins, P.E. Ilha do Cardoso, P.E. Jacupiranga, P.E. Campina do Encantado, P.E. Carlos Botelho, P.E. Intervales and PETAR) were investigated, covering most of the Mata Atlântica remaining in the Ribeira de Iguape basin. Samples were taken during each season of the years 2000 and 2001 using two sampling methods (sieves and traps). Six species of palaemonid shrimps, three atyid shrimps, five aeglid anomuran crabs, and three trichodactylid and one grapsid crabs were collected.