|Budget Amount *help
¥3,500,000 (Direct Cost : ¥3,500,000)
Fiscal Year 2003 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 2002 : ¥900,000 (Direct Cost : ¥900,000)
Fiscal Year 2001 : ¥2,000,000 (Direct Cost : ¥2,000,000)
The egg attachment system of an estuarine crab Sesarma haematocheir is formed on the maternal ovigerous hairs just after egg-laying, and slips off these hairs just after hatching. The stripping is caused by an active factor that we call OHSS (ovigerous-hair stripping substance), which is released by the embryo upon hatching.
OHSS was purified, and its active form had a molecular mass of 25 kDa. The cDNA of OHSS cloned from an embryonic cDNA library was 1759 by long, encoding 492 amino acids in a single open reading frame (ORF). The C-terminal part of the predicted protein was composed of a trypsin-like serine protease domain, with homology to counterparts in other animals of 33-38%. The predicted protein (54.7 kDa) secreted as a zymogen may be cleaved post-translationally, separating the C-terminal from the N-terminal region.
Two years before, we found fantastic phenomena about hatching of an estuarine crab. To investigate mechanisms of hatching in decapod crustaceans, we tried to induce
hatching by use of many kinds of chemicals. Almost chemicals are ineffective, but he found that only acetone and acetonitrile solutions can cause hatching of embryos. No embryos detached from the female hatched under the control water with aeration (400-500 ml of 5‰ artificial seawater). Hatching started around 49 hrs after the treatment with acetone for 10 min, and hatching ratio attained maximum 55 hrs after. All zoeas treated with acetone swam, and their behavior was completely the same as zoeas released from the female.
The ratio of hatching was largely different according to the concentration of acetone. Ninety-five percent hatched among the embryos treated with 60% acetone, and 87% hatched among those treated with 80% acetone. Thus, the solution of 60% acetone was estimated to cause maximum ratio of hatching.
At the first step of this study, we thought that hatching of S. haematocheir embryos could be caused by a substance such as acetone. Hatching is certainly caused by an active factor released from the female. But many experiments suggested that the hatching inducing substance is largely different from a chemical such as acetolie. We are analyzing this substance. Less