| Sesarma dehaani, which plays an important role in ecosystems, is one of the most abundant species in intertidal regions of Dazhi estuary. we comparatively analyze the crabs from internal reproduction systems, the gonad development status, the external morphology and the seasonal changes during 2009 to 2010 collected in Dazhi estuary in laboratory combined the morphology and histology. The aim of this paper is to grasp the dynamic of the population of Sesarma dehaani, to supplement the basic biology and contribute to the regulation and exploration for the crabs resoures. The results are as follows:Firstly, The male reproductive organs consists of paired testes and genital ducts. The testis of Sesarma dehaani were lobular style and consisted of some convoluted lobes made up of numerous lobules. The vas deferens is a tubular duct with branch tubular and becames thick while mature. The sperm cells become encapsulated forming spermatophores with two pellicles in The vas deferens. The testes and vas deferens of Sesarma dehaani showed conspicuous seasonal variation. The female reproductive organs consists of spermatheca, ovary, oviduct, vagina, and vulva. The spermatheca is dorsal style , and the content and external morphology showed conspicuous seasonal variation along with the copulation activity.Secondly, To determine different growth and maturity phase, morphological data collected from October in 2009 to September in 2010, such as carapace, cheliped and abdomen were conducted with cluster and piecewise linear regression analysis. Bivariate discriminant analyses were carried out for classifying any crab as different phases and size at 50% maturity of males and females was estimated by logistic curves. The results are as follows: The cheliped width in males and abdomen width in females both show obviously allometric. The size of 50% morphometric maturity occurred at 16.36mm and 18.22mm carapace width in males and females, respectively. The life history of males shows 3 phases while females only 2 phases according to the different growth rate. A significant change in allometry was detercted in juvenile males with a break point at 11.78mm carapace width; juvenile and adults females overlap in a range of 13.04～18.64mm carapace width. The crabs attain 50% physiological maturity at the size 17.50mm and 17.20mm for females and males respectively. The size of morphological maturity of males is larger than the size of physiological maturity, while the females is just opposite.Thirdly, the carapace width of the reproductive stock of Sesarma dehaani mainly are between 30 to 40 mm, the weight are 15 to 25 g. The copulation season is October, when the vas deferens develop rapidly and attain the peak. The weight of the spermatheca also raise because of the copulation activity. The spawn season is in June, and the brood amount is positive to carapace. The energy store and utilization is in the same trend among the sexes, and attain the peak when in spawn and copulation season, but the energy input for males is higher than females. The hepatopancreas weight add with the CW while the index of the hepatopancreas is in less correlation. The development of the vas deferens and the ovary shows logarithm relationship.The two condition indexes, CF1 and CF2, keep in a balance, the male is higher than female. |
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