GAMETE-RELEASE BY 1-METHYLADENINE IN VITRO IN THE SEA CUCUMBER, LEPTOSYNAPTA INHAERENS

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Abstract
1. The hermaphroditic sea cucumber Leptosynapta inhaerens does contain mature spermatozoa and immature oocytes during the breeding season. In some animals, the gonad contains eggs and few, if any, sperm. 2. Isolated fragments of ovotestes of the sea cucumber were found to shed sperm immediately upon treatment with 1-methyladenine at concentrations higher than 6.3 x 10-7 M. 3. 1-Methyladenine failed to induce both spawning and maturation of immature oocytes within the gonadal fragments, and was unable to effect germinal vesicle breakdown. Treatment of gonadal fragments containing mature oocytes with 1-methyladenine caused a release of these oocytes as was observed with sperm. 4. 1-Ethyladenine was also effective in inducing shedding of sperm at concentrations higher than 1.3 x 10-6 M. The following purine derivatives had no sperm-shedding effect at the concentration of 5 x 10-6 M: adenine, guanine, 6-methylaminopurine, 7-methyladenine, 7-methylguanine, 6-dimethylaminopurine and 1-methyladenosine. 5. Acetylcholine hydrochloride at concentrations greater than 5 x 10-6 M induced shedding of sperm. The sperm-shedding action of both 1-methyladenine (5 x 10-6 M) and acetylcholine (5 x 10-6 M) was completely inhibited in the presence of d-tubocurarine hydrochloride at concentrations higher than 5 x 10-5 M. 6. The present results suggest that 1-methyladenine acts on the gonadal nerve cells or at the neuromuscular junction of Leptosynapta gonads to induce contraction of the gonad, resulting in gamete-shedding.

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