Molt Staging And Methyl Farnesoate Titer During A Molt Cycle Of Swimming Crab Portunus Trituberculatus

Molting is an important feature during the process of growth and development in thecrustaceans,and it is regulated by kinds of hormones such as ecdysteroid and methyl farnesoate.The molt cycle of the crustaceans was divided into four basic periods:postmolt,intermolt,premolt and molt. Observations of morphological changes were successfully used for the study ofdefining molt stages of the swimming crab. The results indicated that the postmolt period wassubdivided into stage A （parts of the body flaccid）,stage B （dorsal carapace edge hard,branchialand cardiac regin still soft） based on shell rigidity changes,and the premolt period was divided intosubstage D₀（R：0-0.4）,substage D₁（R：0.4-0.65）,substage D₂（R：0.65-0.9）,substage D₃（R≈1）,substage D₄（R≈1,the old and new carapace were separated completely） based on the ratio thatwas the distance betten new and old cuticle to old cuticle thickness of the end of dactyl segment inthe swimming leg combining with the growth of the new carapace after dissection;opening of theecdysial sutures in the ventral surface of thoracic and the dorsal of cheliped merus was the omenthat was the beginning of ecdysis.A sensitive analytical method on methyl farnesoate in hemolymph of Portunus trituberculatushas been established using capillary gas chromatography-mass spectrometry. After nonadecanoicacid methylester had been added to hemolymph as inner standard,0.9%NaCl and acetonitrile wereadded to lymph and methyl farnesoate can be extracted with n-hexane effectively, and determinedusing EI-SIM-MS after concentration. The results indicated that methyl farnesoate and the innerstandard can be separated each other on SBP-1column, with sharp peak and rare contamination.The linearity is superior from5.00to200.00ng·mL^-1 and relative coefficient was0.99995, with lowdetection limit of3.27pg. The average recovery rate in hemolymph was95.32%respectively, andthe standard deviation was5.71%respectively.We use the method of capillary gas chromatography-mass spectrometry （GC-MS） tocomplete the process of measuring the methyl farnesoate levels in the hemolymph of theswimming crab during the molt cycle. The results indicated that MF levels in the hemolymph roseduring the premolt stage and declined during the postmolt stages. The average levels of MF forpostmolt stage（A/B） were18.95±10.257ng/ml, it rose to23.41±5.460ng/ml during intermolt,and in the premolt, the MF levels remained high,it respectively reached to110.34±41,754ng/ml,147.09±33.674ng/ml,97.08±46.957ng/ml,133.60±26.152ng/ml,165.30ng/ml in D₀、D₁、D₂、D₃、D₄substages.