Instituto de Ciencias Marinas y Limnológicas, Universidad Austral de Chile, Valdivia, Chile.
Laboratorio de Recursos Acuáticos y Costeros de Calfuco, Universidad Austral de Chile, Valdivia, Chile.
PLoS One. 2019 Jul 23;14(7):e0220051. doi: 10.1371/journal.pone.0220051. eCollection 2019.
Among calyptraeid gastropods, males become females as they get older, and egg capsules containing developing embryos are maintained beneath the mother's shell until the encapsulated embryos hatch. Crepipatella dilatata is an interesting biological model considering that is an estuarine species and thus periodically exposed to elevated environment-physiological pressures. Presently, there is not much information about the reproductive biology and brooding parameters of this gastropod. This paper describes field and laboratory observations monitoring sex changes, brooding frequencies, sizes of brooding females, egg mass characteristics, and embryonic hatching conditions. Our findings indicate that C. dilatata is a direct-developing protandric hermaphrodite, changing from male to female when individuals were between 18 and 20 mm in shell length. At our study site in Quempillén estuary, females were found to be brooding almost continuously throughout the year, having an average maximum of 85% of simultaneous brooding, with a short rest from April through June. No relationship was found between the number of capsules per egg mass and the size of the brooding female. However, capsule size and the number of embryos and nurse eggs were strongly related to female size. The offspring hatched with an average shell length > 1 mm. About 25% of the hatched capsules were found to contain both metamorphosed (juveniles) and non-metamorphosed (veliger) individuals. The sizes of the latter were < 1000 μm. The length of hatching juveniles was inversely related to the number of individuals per capsule, which seems related to differences in the availability of nurse eggs per embryo. Although fecundity per reproductive event of this species is relatively low (maximum approx. 800 offspring per egg mass) compared with those of calyptraeid species showing mixed development, the overall reproductive potential of C. dilatata seems to be high considering that females can reproduce up to 5 times per year, protecting their encapsulated embryos from physical stresses until well-developed juveniles are released into the population, avoiding a dangerous pelagic period prior to metamorphosis.
在盔螺科腹足纲动物中，雄性随着年龄的增长变成雌性，并且含有发育中胚胎的卵囊在母体壳下保持，直到包裹的胚胎孵化。考虑到 Crepipatella dilatata 是一种河口物种，因此会定期暴露在升高的环境生理压力下，它是一个有趣的生物学模型。目前，关于这种腹足动物的生殖生物学和孵化参数的信息并不多。本文描述了监测性转变、孵化频率、孵化雌性个体大小、卵质量特征和胚胎孵化条件的野外和实验室观察结果。我们的研究结果表明，C. dilatata 是一种直接发育的雌雄同体，当个体壳长在 18 到 20 毫米之间时，从雄性变为雌性。在我们在 Quempillén 河口的研究地点，发现雌性几乎全年都在连续孵化，同时孵化的平均最大比例为 85%，从 4 月到 6 月有短暂的休息。我们没有发现卵囊数量与孵化雌性大小之间的关系。然而，卵囊大小以及胚胎和营养卵的数量与雌性大小强烈相关。后代孵化时平均壳长>1 毫米。约 25%的孵化卵囊中含有已变态（幼体）和未变态（面盘幼虫）个体。后者的大小<1000μm。孵化幼体的长度与每个卵囊中的个体数量成反比，这似乎与每个胚胎的营养卵供应差异有关。尽管与表现出混合发育的其他盔螺科物种相比，该物种每次生殖事件的繁殖力相对较低（每个卵质量最大约 800 个后代），但考虑到雌性每年可以繁殖多达 5 次，可以保护其包裹的胚胎免受物理压力，直到发育良好的幼体释放到种群中，避免在变态前经历危险的浮游期，C. dilatata 的总体繁殖潜力似乎很高。
