Analysis of Size, Gonadal Maturation, and Functional Maturity in the Spiny Lobster Panulirus japonicus (Decapoda: Palinuridae)

Abstract

ABSTRACT Relationships between relative growth of various body parts, gonadal maturation, and functional maturity were examined in male and female Panulirus japonicus by regression techniques and histological study of the ovary, testis, and vas deferens. Relative growth of the first pleopod and the first and second pereiopods against the carapace length (CL) is described best by two power regressions for both sexes, except for the male first and second pereiopods, which are described by three power regressions. Sexual differences in relative growth were observed when size exceeded 28-mm CL for the pleopod, and 52- and 54-mm CL for the first and second pereiopods, respectively. In all sizes less than these CLs, regressions between males and females were not significantly different from each other. For female pleopods, an inflection point was observed at 43-mm CL, whereas it occurred at 52- and 54-mm CL in male pereiopods. Females with immature ovaries often were less than 45-mm CL and their gonadosomatic indices were less than 1%, whereas all females greater than and including 45-mm CL had developing or ripe ovaries. In males, sperm were present in the testis and vas deferens of all individuals examined histologically (≧37-mm CL). In individuals greater than and including 54-mm CL, ratios of the diameter of the middle vas deferens to that of the posterior vas deferens were almost constant, and high sperm density was observed in the middle vas deferens, whereas in some individuals less than 54-mm CL sperm were absent in a part of the middle vas deferens and the ratio was low. These histologically observed values correspond well with the inflection points of the relative growth regressions for female pleopods (43-mm CL) and those in male pereiopods (52- and 54-mm CL). This indicates that the inflection points are closely related to gonadal maturation in females and functional maturity in males.