Induction of spawning and oocyte maturation by 5‐hydroxytryptamine in the surf clam

Abstract

Gamete shedding can be induced in male and female surf clams (Spisula solidissima and sachalinensis) by injecting 5-hydroxytryptamine (5-HT) into the gonads. The administration of 0.4 ml of 2.0 mM 5-HT induced spawning in all the clams tested. Shedding of gametes occurred within 2 to 3 min after the treatment and continued for about 40 min. The majority of the shed oocytes retained their germinal vesicles and underwent maturation upon insemination. The fertilized oocytes developed normally to the trocophora stage. The motility of the shed sperm was normal. 5-HT added to the suspending medium to the final concentrations of 10 to 100 pM induced maturation of isolated Spisula oocytes in vitro. The oocytes underwent germinal vesicle breakdown, chromosomal condensation, extrusion of the first and second polar bodies, and pronuclei formation. The neurotransmitter-induced production of maturation-promoting factor. In conclusion, 5-HT induces gamete spawning and initiates oocyte maturation in the s u r f clam.Spawning in the molluscs can be induced by raising the temperature of the seawater (Galstoff, '38, '40; Kinoshita et al., '43; Yamamoto, '51). Although the mechanism of the temperature effect is not known, we hypothesize that a neurotransmitter is released and triggers spawning. The neurotransmitter may be 5-hydroxytryptamine (5-HT) since it induces spawning in scallops of both sexes (Matsutani and Nomura, '82).In the present report, evidence will be presented showing that 5-HT, injected into the gonads of the surf clams of both sexes, induces spawning and that this hormone in vitro induces oocyte maturation. A preliminary communication was presented at the scientific proceedings of the Marine Biological Laboratory, Woods Hole (Hirai et al., '84). MATERIALS AND METHODS 5-HT Spawning assayThe neurotransmitters were dissolved just before use in artificial seawater (ASW, MBL formula) at varying concentrations. A dose of 0.4 ml of the neurotransmitter solution was injected into the gonads and the time of onset and duration of spawning was recorded. The shed oocytes were examined under the microscope for intact germinal vesicles (GV) and sperm motility was evaluated. Oocyte maturation assayThe method of isolation of oocytes from surf clam is described in a previous publication (Sano et al., '79). The test substances were added to the suspending medium at final concentrations of 10 nM to 1.0 mM. After the addition of the neurotransmitters the oocytes were examined under the microscope for the occurrence of germinal vesicle

Environmental occurrence and reproductive effects of the pharmaceutical fluoxetine in native freshwater mussels

“…Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) and exerts its action by reducing the clearance rate of serotonin (5-hydroxytrypamine), a neurotransmitter, in the synapse following nerve signal transmission. Serotonin is a key mediator for a wide variety of physiological functions in mollusks; serotonin regulates reproductive processes including oocyte maturation [9,10], spawning [10,11], and parturition (release of glochidia) [12]. Serotonin, fluoxetine, and other SSRIs have been used to artificially induce spawning in freshwater and marine bivalves for aquaculture purposes [13,14], and have been investigated as a potential chemical control mechanism (i.e., disruptor of reproduction) for exotic bivalve species like the zebra mussel Dreissena polymorpha [9,15].…”

Roles of extracellular ions and pH in 5-HT-induced sperm motility in marine bivalve

“…Since the first discovery of the stimulatory effects of serotonin (5-hydroxytryptamine creatinine sulfate (5-HT) in the reproduction of marine bivalve mollusks (Matsutani & Nomura 1982), 5-HT potency to induce spawning, gamete release, and maturation of oocytes have been extensively studied in various species (Osanai 1985, Hirai et al 1988, Osada et al 1998, Tanabe et al 2006, Yuan et al 2012. 5-HT has been localized immunohistochemically in the gonad and its concentrations have also been determined at various stages of gonadal development (Masseau et al 2002, Garnerot et al 2006.…”

Synergistic activation by serotonin and GTP analogue and inhibition by phorbol ester of cyclic Ca2+ rises in hamster eggs.

“…Biological significance of 5-HT 5-HT is an inducer of oocyte maturation in the surf clam Spisula (Hirai, Kishimoto, Kadam, Kanatani & Koide, 1988). 5-HT is also contained in sea urchin embryos and its content varies rhythmically during development in time with the cell cycle and early embryogenesis (Renaud, Parisi, Capasso & De Prisco, 1983).…”