Diet and internal physiological changes of female orange mud crabs, Scylla olivacea (Herbst, 1796) in different ovarian maturation stages.

Recently, there has been a growing interest in the ovarian maturation of mud crabs, genus Scylla. Studies regarding the factors that affect ovarian maturation in mud crabs, however, are still lacking. This study, therefore, evaluates the relationship between diet and internal physiological changes of female orange mud crabs, Scylla olivacea. Sixty female adult S. olivacea were sampled from Setiu Wetland, Malaysia. Foreguts were sampled to study fullness and content. The hepatopancreas was sampled to study digestive enzyme activity, biochemical composition, and histology. Ovaries were sampled to study ovarian biochemical composition and histology. Foregut fullness data suggest that there is an increase in feeding with advancing ovarian maturation in mud crabs. Data for foregut contents indicated that when the ovary was in Stage 3 of maturation the diet was animal-based. The activity of amylase, cellulase, lipase, and trypsin during Stages 1 and 4 of ovarian maturation were less than during Stage 3 of ovarian maturation. Biochemical composition (protein and lipid) was greater during Stage 3 of ovarian maturation. Histological analysis of the hepatopancreas indicated an increase in hepatopancreas tubules, B and R cells during Stage 3 as compared with Stage 1 of ovarian maturation. Histological analysis of the ovary indicated increases in oocyte diameter due to concentrated large yolk globules. Based on these results, it is concluded that vitellogenesis mainly occurred during Stage 3 of ovarian maturation, based on evidence of increased feeding with the diet being predominantly animal-based. Likewise, digestive enzyme activities, proteins, lipids, B cells, and R cells were all greater during Stage 3 of ovarian maturation.