卵胎生有肺類ナミコギセルガイの雌雄同体現象の研究 : I 成長指標としての螺層階数

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タイトル別名
  • Studies on Hermaphroditism of the Ovoviviparous Pulmonate, Euphaedusa tau (Bottger) : I Shell Whorls as a Growth Parameter
  • 卵胎性有肺類ナルコギセルガイの雌雄同体現象の研究-1-成長指標としての螺層階数
  • ランタイセイ ユウ ハイ ルイ ナルコギセルガイ ノ シユウ ドウタイ ゲンシ

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Euphaedusa tau (Bottger)(Stylommatophora, Clausiliidae) is a hermaphroditic and ovoviviparous snail. As the first step for studies on the hermaphroditism, we attempted to establish a practical method for determining the growth stages of this species. On the assumption that the number of shell whorls is a useful growth parameter, we made the following observations. Snails were obtained from the campus of Nara Women's College at Nara City five times at various seasons of 1978 and 1979. Growth of the snail was divided into eight stages according to the number of shell whorls. The stages were named in order of increasing in number of the whorls as Stage 3, 4, -, 9 and 10, respectively. The shell height and breadth were measured in all specimens collected. Snails at the same stage were almost same in height and breadth. The seasonal fluctuations of the values were very small. Therefore, the expression of the growth stage by means of the number of shell whorls will facilitate a precise approach to the future study on the hermaphroditism of this species and make it easy to collect some batches of animals all at the same stage from samples without laborious sorting. Spermatogenesis occurred in some snails at Stage 7, and he percentage of snails with spermatozoa in the ovotestis increased at more advanced stages. Most of the snails with embryos and/or young snails in the oviduct were found in those at Stage 10. It means that in a population of Euphedusa tau, the Stage 10, which produces youngs, directly involves in reproductive activity to sustain the popula ion.

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