Arthropods (Sep 2013)
Reproductive characteristics of a brachyuran crab, Grapsus tenuicrustatus (Herbst, 1783) (Decapoda: Grapsidae) found in Talim Bay, Batangas, Philippines
Abstract
The study determined some reproductive characteristics of a brachyuran crab, Grapsus tenuicrustatus (Herbst, 1783), one among the most widespread and diverse groups of invertebrates. Results revealed that there were more males (52.94%) than females (47.06%) collected at the study sites with a sex ratio of 1:1.13. Thirty percent (30%) of the samples were ovigerous females. Ovigerous females have the largest caraface length, CL, (31.25 +- 1.43) compared with the males (22.14 +- 0.726) and non-ovigerous females (26.63 +- 1.12). Based on one-way ANOVA, the differences were significant. Difference between non-ovigerous and ovigerous females was also found significant based on t-test for independent samples. There was a non-conspicuous bi-modal size distribution for all the crabs, with non-normal distributions for all crabs and for males, but not when all females or ovigerous females only were grouped together. The size-frequency distributions of males and females are significantly different from each other similar with that observed between the size-frequency of ovigerous and non-ovigerous females. There were more ovigerous crabs belonging to the first year age class (CL = 16 - 33) (53.13 %) than those that belong to the older class (CL = 34 - 43) (46.88 %). Fecundity ranged from 4400 (CL = 16 mm) to 26400 (CL = 43 mm) eggs. Egg volume ranged from 0.40 ml to 2.40 ml, egg diameter from 1.1 um to 5.0 um with an average diameter of 3.170 um and egg count from 4400 to 26400 with a mean of 12684 eggs. Egg number was positively correlated with female size.
