• Regulation of ecdysteroid and vitellogenin levels during the molt and reproductive cycles of female dungeness crab, Cancer magister

      Thomton, Jamie David (2005-12)
      The reproductive cycle of Dungeness crabs is complicated by the requirement for molting prior to mating. The temporal requirements for molting and ovarian maturation may prohibit an annual reproductive cycle in a proportion of crabs. The goal of this study was to quantify temporal concentrations of circulating ecdysteroids and vitellogenins in female crabs during an annual cycle. Hemolymph in laboratory maintained crabs was sampled to assess physiological state (molting or reproduction). In laboratory crabs, ecdysteroid concentrations were low during intermolt (20.3 ng/ml), increased to maximal levels 15 days before ecdysis (1,886.5 ng/ml), and declined to low concentrations (<90 ng/ml) 5 days before ecdysis. Premolt duration was 150 days, with peak molting in November. Vitellogenin concentrations increased 6-fold during induced (via eyestalk ablation) ovarian maturation over a 90 ± 7.4 day vitellogenic period, and 4-fold for natural ovarian maturation over a 75 to 100 day period. The capability to predict ecdysis 150 days before molt and spawning 100 days before egg extrusion through hemolymph analysis is useful in molt and reproductive assessment of Dungeness crab populations. Additionally, in a preliminary study, reproductive failure and shell-disease were induced by physiological stress due to captive environmental conditions