1995 Fiscal Year Final Research Report Summary

BIOLOGICAL ASPECTS OF RESTING EGG FORMATION OF MARINE ROTIFERS AND ITS APPLICATION TO FINFISH HATCHERIES

Research Project

Project/Area Number	06660245
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	General fisheries
Research Institution	NAGASAKI UNIVERSITY
Principal Investigator	HAGIWARA Atsushi NAGASAKI UNIVERSITY FACULTY OF FISHERIES DEPARTMENT OF FISHERIES ASSOCIATE PROFESSOR, 水産学部, 助教授 (50208419)
Project Period (FY)	1994 – 1995
Keywords	ROTIFERA / RESTING EGG / PRESERVATION / MIXIS INDUCTION / MATING BEHAVIOR / RESTING EGG PRODUCTION / SEX PHEROMONE / LARVAL REARING
Research Abstract	Observations on mating behavior between different groups indicated that there is reproductive isolation between B.plicatilis and B.rotundiformis and between B.plicatilis and SS strains. In contrast, copulation was observed between B.rotundiformis and SS-strains. Thus, there is no evidence that SS-strains are a new marine Brachionus species, and most likely should be included in B.rotundiformis. The efficiency of resting egg production can be improved by employing the semi-continuous culture method. Some semi-continuous cultures collapsed on 15-20th days due to the bacterial effect. However, the rotifer culture was stabilized by placing filtration mats to remove organic materials. Thus harvest of 8.1x10^2 resting eggs/day/g (dry weight) Nannochloropsis oculata was achieved, which is 3.0 times more efficient than from batch cultures. Resting eggs of B.rotundiformis, however, were not mass produced after the exchange of culture water.