Reproductive aspects and fecundity in the freshwater crabs Trichodactylus borellianus (Brachyura, Trichodactylidae) in La Plata system, Argentina.

KÖNIG NATALIA; WILLINER VERONICA

La Serena, Chile

Congreso; The Crustacean Society Mid-Year Meeting 2007; 2007

Universidad Catolica del Norte-Crustacean Society

Trichodactylus borellianus is a common freshwater crab species of the Trichodactylidae family from South America. Its natural habitat is the aquatic vegetation mainly roots and leaves of Eicchornia sp. Besides, the species occur on objects in the sediment of the margins of shallow lakes, streams and rivers. The objective of this study was to analyze the fecundity and reproductive aspects of this freshwater crab in La Plata systems. This study was carried out in three environments of the Paraná river according to a transect between the main channel and the floodplain. Trichodactylus borellianus populations were sampled during 2001, 2002, 2003 y 2004. Individuals were separated into females, males and juveniles. The presence of ovigerous females was recorded at each sampling occasion. In the laboratory, the following procedure was followed for each crab: carapace width (CW) was determined and the egg mass was removed and all eggs were counted and the size was measured with TPSdig software after digital photography. The relationship between fecundity and carapace width was analyzed by linear regression. A significantly greater number of females were observed in all samples. Ovigerous females appeared in late winter (August), being present until March with a higher occurrence in November and January. The observed carapace width of the smallest ovigerous female is 8.5 mm. The fecundity of T. borellianus  female caught at La Plata system was 101 ± 26 eggs. The mean egg size was 0. 93 ± 0.079 mm diameter. The relationship between body size and fecundity showed a significant correlation. The egg eclosion does not occur in a same day, being this asynchronicity observed according to the maturity degree and on the location below of the pleopods. Trichodactylus borellianus is a common freshwater crab species of the Trichodactylidae family from South America. Its natural habitat is the aquatic vegetation mainly roots and leaves of Eicchornia sp. Besides, the species occur on objects in the sediment of the margins of shallow lakes, streams and rivers. The objective of this study was to analyze the fecundity and reproductive aspects of this freshwater crab in La Plata systems. This study was carried out in three environments of the Paraná river according to a transect between the main channel and the floodplain. Trichodactylus borellianus populations were sampled during 2001, 2002, 2003 y 2004. Individuals were separated into females, males and juveniles. The presence of ovigerous females was recorded at each sampling occasion. In the laboratory, the following procedure was followed for each crab: carapace width (CW) was determined and the egg mass was removed and all eggs were counted and the size was measured with TPSdig software after digital photography. The relationship between fecundity and carapace width was analyzed by linear regression. A significantly greater number of females were observed in all samples. Ovigerous females appeared in late winter (August), being present until March with a higher occurrence in November and January. The observed carapace width of the smallest ovigerous female is 8.5 mm. The fecundity of T. borellianus  female caught at La Plata system was 101 ± 26 eggs. The mean egg size was 0. 93 ± 0.079 mm diameter. The relationship between body size and fecundity showed a significant correlation. The egg eclosion does not occur in a same day, being this asynchronicity observed according to the maturity degree and on the location below of the pleopods.