Bioassay and Preliminary Characterization of Ovigerous-Hair Stripping Substance (OHSS) in Hatch Water of Crab Larvae.

Hatch water (the filtrated medium into which zoea larvae have been released) of the estuarine terrestrial crab Sesarma haematocheir (akate-gani) contains a substance that causes premature detachment of embryos from ovigerous females. Detachment occurs when the ovigerous hairs along the female's ovigerous setae slip out of the investment coat that binds them to the embryos through stalks, or funiculi. The active factor, which I call ovigeroushair stripping substance (OHSS), is released outside of the egg capsule at the time of hatching, and is not secreted by the female. This study describes the results of a quantitative assay for measuring the activity of OHSS. Activity is measured as the percentage of hairs on a seta that can be induced to slip out of the coat without damage. Experiments with an extract of crushed embryos indicated that OHSS is present up to 2 days before hatching. Its activity was destroyed by heat and trypsin, suggesting that it is a protein. Its molecular size was estimated by gel filtration to be 15-20 kDa in S. haematocheir and 30 kDa in S. pictum. Reciprocal tests among different species indicated that OHSS occurs widely in intertidal and estuarine crabs.