[Effect of organ ablation on oogenesis in the crab Eriocheir sinensis in the natural state and after removal of Y organ]

Ecdysteroids in the embryos and sera of the crabs, Cancer magister and C. anthonyi

Ecdysteroids in the embryos and sera of ovigerous brachyuran crabs, Cancer magister and C. anthonyi, were measured and characterized by radioimmunoassay (RIA) and high-performance liquid chromatography (HPLC). C. magister embryos displayed a biphasic pattern of ecdysteroid fluctuation during development; titers decreased until mid embryogenesis and then increased and peaked prior to hatching. HPLC-RIA analysis indicated increasing ecdysone concentrations from mid embryogenesis to hatching. Endogenous biosynthesis of ecdysone by the embryos is suggested. In contrast, ecdysteroid titers in the embryos of C. anthonyi showed a steady decrease from very high initial concentrations. The decrease in titers of ecdysone and 20-hydroxyecdysone is suggestive of utilization of maternally derived ecdysteroids rather than endogenous biosynthesis during the shorter embryogenic period for C. anthonyi. Ecdysteroid concentrations did not differ with respect to location of the embryo within the egg mass. Serum ecdysteroids in C. magister females generally showed a monotonic pattern during brooding. However, for C. anthonyi females, increasing and decreasing titers were observed during the brood and interbrood periods, respectively. These fluctuations suggest mobilization of the ecdysteroids to the ovaries for subsequent storage and utilization during embryogenesis. The evolutionary significance of these differing patterns of ecdysteroid metabolism in these congeners is discussed.

Neurohormonal control of ecdysteroid biosynthesis by Carcinus maenas Y-organs in vitro, and preliminary characterization of the putative molt-inhibiting hormone (MIH)

Using simple culture techniques, the effects of neurosecretory tissue, sinus gland-conditioned media, and sinus gland extracts upon the biosynthesis of ecdysteroids by Carcinus maenas Y-organs in vitro were investigated. The sinus glands were found to be a major source of a factor which profoundly repressed ecdysteroid synthesis and which did not appear to be species-specific within other brachyurans examined (Liocarcinus, Cancer). It is suggested that the inhibitory factor is produced by the neurosecretory tissues of the medulla terminalis. It is argued that the inhibitory factor is the putative molt-inhibiting hormone (MIH). Partial characterization revealed that MIH is a heat-stable, trypsin-sensitive neuropeptide, eluting on a Sephadex G-50 gel in a range of approximately 6-14 kDa. By consideration of the dose-response characteristics, it is estimated that MIH may be active in the subpicomolar range.