ONTOGENIC EXPRESSION OF CRUSTACEAN FEMALE SEX HORMONE (CFSH) AND ITS FUNCTIONAL ROLE IN DEVELOPING FEMALE SPECIFIC-SEX CHARACTERISTICS IN THE BLUE CRAB, Callinectes sapidus  

Crustacean female sex hormone (CFSH) regulates the development of adult female specific-sex characteristics that are specifically involved in parental care of female blue crab, Callinectes sapidus.  The presence of CasCFSH during the embryogenesis of this species is seen in the embryos  which contain CasCFSH in the sinus gland at the hatching-imminent stage.  Because crustacean sex dimorphism develops gradually during the life cycle, we aim to establish a relationship between the levels of CasCFSH expression and the development of phenotypes specific to female C. sapidus during its life cycle.  The levels of CasCFSH transcripts steadily increase throughout early life from stages 3-4 to pre-pubertal stage of females, while showing a decrease only at crab stages 15-16.  The highest levels of CasCFSH transcripts occur during the pre-pubertal stage, and are ~5.6 fold greater than those of adults.  The first visible secondary sex characteristics of females, a pair of gonopores or triangular abdomen and 4 pairs of pleopods, are seen as early as stage ~3 (CW 5-7 mm) or 5 (CW 8-10 mm), respectively.  The morphological features that are associated with adult females and manifest only at the completion of pubertal-terminal molt develop gradually throughout the pubertal molt cycle.  Specifically, spermathecae develop at early premolt stage (D₀); ovigerous and plumose setae on pleopods at premolt stage (D_0-4); gonopores and abdomen at the completion of ecdysis.  Knockdown of CasCFSH transcripts by injection of dsRNA-CasCFSH at specific pre-pubertal molt stages further supports the conclusion that the gradual development of adult-specific morphological features depends on the constant presence of CasCFSH.