. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 10 6 10 5 10 •[Serotonin, M) •. 10 • ' 10-6 10-5 ^^— [8 OH-DPAT. M] Figure 5. Percent GVBD (mean + ) in .\fuctni oocytes treated with (A) 5-HT. or sperm as a positive control (» = 6 females) and (B) X- OH-DPAT (n = 3 females). SW = seawater. HT control (/-test, / = , P < ), and the 1 mM 5- HT control (/-test, t = , P alpha-methyl 5-HT > 8-OH-DPAT ^> TFMPP > 1-methyl-chlorophenyl biguanide. These ex- periments support a growing body of literature indicat- ing that 5-HT receptors mediating reproductiv
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 10 6 10 5 10 •[Serotonin, M) •. 10 • ' 10-6 10-5 ^^— [8 OH-DPAT. M] Figure 5. Percent GVBD (mean + ) in .\fuctni oocytes treated with (A) 5-HT. or sperm as a positive control (» = 6 females) and (B) X- OH-DPAT (n = 3 females). SW = seawater. HT control (/-test, / = , P < ), and the 1 mM 5- HT control (/-test, t = , P alpha-methyl 5-HT > 8-OH-DPAT ^> TFMPP > 1-methyl-chlorophenyl biguanide. These ex- periments support a growing body of literature indicat- ing that 5-HT receptors mediating reproductive pro- cesses in bivalves show a mixed 5-HT,/5-HT: pharma- cological profile, unlike any described for vertebrates (, Kadam el a/.. 1991; Krantic et a!.. 1991; Fong el ai. 1993;Gobet rf<//., 1994). In bivalve molluscs, all oocytes are initially arrested at prophase-I within the ovary. At the time of spawning, oocytes are released either at prophase-I or metaphase-I. In species such as Mytilus edidis, Dreissenapolymorpha, and Ruditapes philippinarum, prophase-I-arrested oo- cytes reinitiate meiosis (including GVBD) under the in- fluence of neurohormones such as 5-HT. Such oocytes are spawned at metaphase-I where they remain until fer- tilization. By contrast, species such as Spisu/a solidis- sinia. Barnea Candida, and Mactra chinensis spawn pro- phase-I arrested oocytes which, in nature, only reinitiate meiosis after fertilization. In the oyster Crassostrea gi- gas, both prophase-I and metaphase-I oocytes can be fer- tilized, although in nature the latter occurs. Oocytes from Spisula spp. have provided good mate- rial for the study of oocyte maturation and other cell cy- cle processes (Hirai el a/., 1988; Kadam and Koide, 1989; Kadam el ai. 1990; Krantic el ai. 1991; Dube, 1992). In Spisula, both spawning and GVBD can be in- duced by 5-HT and 5-HT agonists. However, consider- ing that Spisu/a spawns prophase-I oocytes, the fact that 5-HT can induce GVBD seems puz
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