Schärer L, Karlsson L M, Christen M, Wedekind C
Abteilung Verhaltensökologie, Zoologisches Institut, Universität Bern, Hinterkappelen, SwitzerlandStereology Unit, Institute of Anatomy, Universität Bern, Bern, SwitzerlandInstitute of Cell, Animal and Population Biology, University of Edinburgh, West Mains Road, Edinburgh, Scotland, UK.
J Evol Biol. 2001 Jan 8;14(1):55-67. doi: 10.1046/j.1420-9101.2001.00263.x.
Most models of sex allocation distinguish between sequential and simultaneous hermaphrodites, although an intermediate sexual pattern, size-dependent sex allocation, is widespread in plants. Here we investigated sex allocation in a simultaneous hermaphrodite animal, the tapeworm Schistocephalus solidus, in which adult size is highly variable. Sex allocation was determined using stereological techniques, which allow measuring somatic and reproductive tissues in a common currency, namely volume. We investigated the relationships between individual volume and allocation to different reproductive tissues using an allometric model. One measure of female allocation, yolk gland volume, increased more than proportionally with individual volume. This is in contrast to the measure of male allocation, testis volume, which showed a strong tendency to increase less than proportionally with individual volume. Together these patterns led to sex allocation being strongly related to individual volume, with large individuals being more biased towards female allocation. We discuss these findings in the light of current ideas about size-dependent sex allocation in, primarily, plants and try to extend them to simultaneous hermaphrodite animals.
大多数性别分配模型区分了顺序雌雄同体和同时雌雄同体，尽管一种中间性模式，即大小依赖性性别分配，在植物中广泛存在。在这里，我们研究了一种同时雌雄同体动物——绦虫实尾蚴的性别分配，其中成年个体大小差异很大。使用体视学技术确定性别分配，该技术允许以共同的量度，即体积，来测量体细胞和生殖组织。我们使用异速生长模型研究了个体体积与不同生殖组织分配之间的关系。雌性分配的一个指标，即卵黄腺体积，与个体体积的增长比例超过了相应比例。这与雄性分配指标，即睾丸体积形成对比，睾丸体积显示出增长比例小于个体体积增长比例的强烈趋势。这些模式共同导致性别分配与个体体积密切相关，大型个体更倾向于雌性分配。我们根据目前主要关于植物中大小依赖性性别分配的观点来讨论这些发现，并试图将其扩展到同时雌雄同体动物。
