Ecdysteroid Titers During the Molt Cycle of the Blue Crab Resemble Those of Other Crustacea

Callinectes sapidus is the only true crab (brachyuran) whose pattern of ecdysteroid titers has been described as departing from the pattern seen in other decapods. While ecdysteroids in other crabs reach a peak just prior to ecdysis, those of C. sapidus were claimed to reach their maxima after ecdysis. The data reported here challenge these findings. We have measured ecdysteroids in hemolymph, ovaries, and whole animal extracts of blue crabs using a radioimmunoassay. In hemolymph and whole animals, ecdysteroid levels rose during premolt to a maximum at stage D3. Ecdysteroids declined rapidly from late premolt stage D4 through postmolt stage A2, increased slightly at postmolt stage B, and returned to low levels where they remained during intermolt stage C. Ecdysteroid levels in males and immature females were not significantly different but mature females, having reached a terminal anecdysis, had significantly lower ecdysteroid levels. Ovaries of mature females accumulated ecdysteroids during vitellogenesis while the concentration of ecdysteroids in hemolymph was low.