Effect of methyl farnesoate hormone on moulting period of orange mud crab, Scylla olivacea (Herbst, 1796)

Abstract

Methyl farnesoate (11:F), a hormone synthesized by the mandibular organ (MO) of crustacean plays an important role in regulating moulting. By identifying a practical and economic dosage, moulting estimated time without hyperecdysonism or perturbation can be obtained. In addition, a wide range of commercial applications such as propagation and soft-shelled production can also be developed. The objectives of this study are to examine the effect of the MF hormone on orange mud crab, S. olivacea in the aspects of moulting period, carapace width (CW) increment and the survival rate. Samples were divided into three groups 'where control group (C) treated with MF vehicle solvent (ethanol), Treatment l(Tl) treated with 3 µg of MF and Treatment 2 with 9 µg of 11F in each crab per week. The experiment was lasted 100 days while the effect of MF on each aspect was observed and analyzed. In the aspect of moulting period, administration MF had no effect in accelerating the moulting period. In term of gender, 11F did have the tendency to accelerate moulting duration in females (p = 0.018) but not in males (p = 0.18) however only females in Tl significantly moulted faster than males (p = 0.00) while other groups did not show any differences (p > 0.05). Female crabs have a positive response towards 11F in accelerating moulting period with lower doses (3 µg) but it tends to inhibit the moulting process in female crabs as the doses increased to 9 µg. Three different doses of hormone did not cause a tendency to affect CW increment as there was no significant observed in the increment (p = 0.274). In term of genders, female crabs had significant difference (p < 0.05) in CW increment for C group and Tl but not in T2 (p = 0.759). The effect of MF seemed not related to CW increment and may easily be affected by external factors.