MORPHOMETRY AND SEXUAL MATURITY OF THE PURPLE STONE CRAB, Platyxanthus crenulatus (BRACHYURA, PLATYXANTHIDAE) IN MAR DEL PLATA HARBOUR

FARIAS NAHUEL; SPIVAK EDUARDO; LUPPI TOMAS

Coquimbo Chile

Congreso; The crustacean society mid-year; 2007

Platyxanthus crenulatus, a crab endemic of the Southwestern Atlantic distributed from 44 to 23ºS, is commonly found in the intertidal and subtidal of Argentine rocky shores. From May 2006 to May 2007 we collected 254 individuals of P. crenulatus (106 females and 148 males) in Mar del Plata harbour whit SCUBA diving. We measured the carapace width (CW), the length of male chelae (propodus of the crusher, PL) and gonopod, and the width of the sixth abdominal segment (AW) of females. Finally, we registered the presence/absence of ovary of females and the presence/absence of spermatophores in the middle portion of the vas deferens of males. We used the piecewise linear regression tool of the STATISTICA7 program to detect breakpoints on the regression lines and estimate the size at sexual maturity, using carapace width as the reference dimension. For both, morphometrical and gonadal maturity, CW50% was estimated by fitting the logistic equation with Microsoft Excel´s Solver program. In both sexes gonadal and morphometrical maturity do not differ. Males shown a significative change in allometry of the major propodus length approximately at 40,66mm CW and the gonadal maturity was near to 40,69mm CW,  while in females, sixth abdominal segment width showed a possible size at sexual maturity at similar at 38,79mm CW and a gonadal maturity near to 40,83 mm CW.