Ecological Studies on Interspecific Relationships by Chemical Signals in Rocky Shore Ecosystem

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Feeding-deterrent activities of the acetone extracts from the brown algae Dictyopteris latiusucula, Zonaria diesingiana Padina arbo-ressens, P. minor, and P. japonica was tested on the abalone Haliotis discus hannai by the cellulose plate bioassay method.The neutral and acidic fraction of acetone extracts showed a marked feeding-deterrent activities in all species.The life history of the brown alga Dilophus okamurae which produced the nine diterpenes as an active feeding-deterrent compounds have been ascertained as follows : the sporophytes germed from zygotes in June and forms reduction divided tetraspores in next September of sixteen months after germination, and male and female gametophytes germed from tetraspores in November and formed gametes (eggs and sperms) in next May.The thirty seven species of benthic invertebrates inhabited the D. okamurae population.They were classified the three groups by seasonal variation of their densities and standing crops compared with seasonal variation of D. okamurae population standing crops : synchronize, independence and appearance of only juveniles.