|
PHILIPPINES
Histological and biochemical analyses
Ovarian maturation in wild-sourced and pond-grown
Scylla serrata was studied in terms of gross morphology, histological appearance, and nutrient profiles. Ovarian maturation was classified into six stages (immature to spent). During maturation, protein, lipids, minerals, and ascorbic acid were accumulated in the ovaries, which suggests that these nutrients are needed in reproduction. In wild-sourced crabs, the essential amino acids arginine, leucine, methionine, and valine increased between the immature and mature ovaries; triglycerides and phosphotidylcholine were accumulated; and the concentrations of highly unsaturated fatty acids (docosahexaenoic acid, eicosapentaenoic acid, and arachidonic acid) were high. Lipids decreased as eggs hatch to zoea indicating the importance of lipids during embryonic development. Information on nutrient profiles will serve as basis for the improvement of crab broodstock and larval diets.
Reproductive performance of S. serrata fed graded levels of dietary lipids with or without natural food supplement
|
Adult pond-sourced
S. serrata (625 + 53.3 g body weight) were fed artificial diets with squid oil and soybean lecithin (2:1 ratio) at three levels (6, 9 and 12%) with or without supplementation of natural foods (mussel, squid or fish). Broodstock fed natural food served as the control. After three months, broodstock fed natural food alone and diets with 6, 9 and 12% lipid with natural food supplementation had better performance than those fed artificial diet alone. |
S. serrata broodstock
|
Alternative live and artificial feeds for Scylla spp. larvae
Rotifers are routinely used as feed for crab larvae and as an alternative; the efficacy of oyster
(Crassostrea iridalei) trocophores was evaluated. Trocophores were acceptable as food but survival and growth were better in larvae fed rotifers alone or trocophores in combination with
Artemia.
Growth and survival of mud crab larvae fed artificial diets of various physical preparations (crumbled, granulated, drum-dried and window refractance dried) were evaluated. All stages of zoea ingested the artificial diets within 30 min of initial feeding with no difference to those given live food as control (rotifers from zoea 1 to 5 +
Artemia from zoea 3 to megalopa). The survival was higher in larvae fed crumbled and granulated diets in two experiments using
S. serrata and S. tranquebarica.
Functional and physiological maturity of Scylla
spp.
Hatchery-reared S. serrata, S. tranquebarica and
S. olivacea juveniles were grown to maturity in ponds, meristic measurements were made, and the gonads and external sexual characters were monitored. The abdomen width, carapace length, and propodus height, thickness and length were each plotted against the internal carapace width (ICW). There is an increase in the abdominal width per unit increase in ICW of females in the three species. The propodus height and thickness are greater in males than females per unit increase in ICW. Mating readiness of
S. olivacea occurs in smaller body sizes than those in
S. tranquebarica and S. serrata.
return to
top |
