. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 28 P. P. FONG ET AL. purposes, but also to compare reproductive mechanisms in closely related species. We tested various serotonin an- alogs for effects on spawning and oocyte maturation in M. chinensis. Our experiments revealed that, as in Spisula. 5-HT and related compounds are potent induc- ers of spawning, but unlike Spisnla. serotonergic com- pounds do not cause significant GVBD in Mactra. Materials and Methods Animals Mature Mactra chinensis (4-6 cm shell length) were collected in May 1995 by fishermen in Tokyo Bay, Ch
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 28 P. P. FONG ET AL. purposes, but also to compare reproductive mechanisms in closely related species. We tested various serotonin an- alogs for effects on spawning and oocyte maturation in M. chinensis. Our experiments revealed that, as in Spisula. 5-HT and related compounds are potent induc- ers of spawning, but unlike Spisnla. serotonergic com- pounds do not cause significant GVBD in Mactra. Materials and Methods Animals Mature Mactra chinensis (4-6 cm shell length) were collected in May 1995 by fishermen in Tokyo Bay, Chiba Prefecture, and immediately shipped to the Asamushi Marine Biological Station. Animals were maintained in running seawater until used. All experiments were per- formed from 23 to 30 June 1995. Spawning and G \ 'BD assays To induce spawning, animals were injected in the foot with ml of 5-HT, 5-HT ligands, or natural seawater (SW) as a control. Immediately after injection, animals were placed in plastic containers containing 200 ml of SW, and observed for evidence of spawning. All spawn- ing experiments lasted one hour, after which all non- spawners were injected with 5-HT (determined to be a good inducer of spawning after initial experiment) as a test for their ability to spawn. The effect of mianserin, a vertebrate 5-HT;. antagonist that inhibits a number of reproductive processes in ma- rine and freshwater bivalves, was tested as follows. Vari- ous concentrations of antagonist were injected into the foot for 15-20 min before a subsequent injection of 5- HT combined with mianserin at the same concentration as in the first injection. Responses were monitored for 1 h after the second injection. For the analysis of GVBD, prophase-I oocytes were dissected from ovaries or, on one occasion, obtained by a natural spawning. In both cases, released oocytes had large germinal vesicles that were clearly visible (Deguchi and Osanai, 1994). GV oocytes were pipetted into wells of a 2
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
