ABSTRACT We analyzed the spatio-temporal variations of the abundance, distribution and the population structure of Hexapanopeus paulensis Rathbun, 1930 from the southeastern Brazilian coast. Monthly samples were taken from January 1998 to December 1999 at Ubatumirim, Ubatuba and Mar Virado bays. A total of 1084 individuals were obtained, 76 specimens at Mar Virado, 322 at Ubatuba and 686 at Ubatumirim. It was possible to verify an association between the abundance of H. paulensis and bottom temperature (positive correlation), grain size of sediment and organic matter content (both negatively). This explains the higher number of individuals in the stations nearest to the continent (with higher temperature values and heterogeneous substrate). Juveniles were recorded throughout the study period, constituting 39.5% of the sampled population, which highlights the importance of the region (especially Ubatumirim Bay, due the highest abundance) for the establishment of the species. Only females occupied the largest size classes, which could mean differential mortality between the sexes or growth rate. Nevertheless, further studies should be accomplished to a better comprehension of such difference.

In this study, we estimated the size at onset of maturity (carapace width, CW50) and analyzed the relative growth of some body parts and the heterochely of the mud crab Hexapanopeus paulensis. A total of 800 crabs were collected, from January 1998 to December 1999, on the southeastern coast of Brazil. Each specimen was sexed and measured. CW50 was estimated to be 6.7 mm in males and 6.3 mm in females. Carapace length growth was negatively allometric in both sexes. Cheliped length and height was positively allometric for both males and females. Gonopod growth was isometric (b = 1) and negatively allometric (b < 1) in both juvenile and adult males, respectively. Abdomen relative growth was positively allometric (b > 1) for both juvenile and adult females. In males and females, the right cheliped was larger and higher than the left cheliped. Such heterochely may be related to the feeding habits of H. paulensis. Most xanthoid crabs, including the studied species, feed upon mollusks with dextral shells, which require complicated handling. In this sense, the heterochely in H. paulensis might facilitate the food manipulation.

En esto estudio se investigó la talla de primera madurez sexual (ancho del caparazón CW50), crecimiento relativo de varias estructuras corporales y la ocurrencia de heteroquelia en machos y hembras de Hexapanopeus paulensis. Se recolectó un total de 800 ejemplares, de enero 1998 diciembre 1999 en la región de Ubatuba, costa sureste de Brasil. Cada cangrejo recolectado fue sexado y medido. El CW50 ocurre a los 6,7 mm en machos y 6,3 mm en hembras. En machos juveniles y adultos, el crecimiento relativo (basado en el CW) del gonopodio fue isométrico (b = 1) y alométrico negativo (b < 1), respectivamente. El crecimiento relativo del abdomen fue alométrico positivo (b > 1) en hembras juveniles y adultas. El crecimiento relativo del ancho del caparazón fue alométrico negativo en los dos sexos. El alto y largo del quelípedo presentaron alometria positiva. El quelípedo derecho (largo y alto) fue más grande que el quelípedo izquierdo tanto en los machos como hembras. Consecuentemente, H. paulensis exhibe heteroquelia, lo que sugiere especialización de los quelípedos en relación a su hábito alimentario. Tanto H. paulensis como otros cangrejos xantoideos se alimentan de moluscos con conchas dextrógiras, y la destrucción de dichas conchas requiere de un manejo complejo de sus quelípedos. De este modo, los quelípedos heteroquélicos pueden facilitar la manipulación del alimento en el cangrejo H. paulensis.