Department of Biology, Friday Harbor Laboratories, University of Washington, Friday Harbor, Washington.
J Exp Zool B Mol Dev Evol. 2021 Apr;336(3):221-230. doi: 10.1002/jez.b.22929. Epub 2020 Jan 30.
Many colonial marine animals care for embryos by brooding them on or in their bodies. For brooding to occur, features of the animals must allow it, and brooding must be at least as advantageous as releasing gametes or zygotes. Shared features of diverse colonial brooders are suspension feeding and a body composed of small modules that are indefinitely repeated and can function semi-autonomously, such as polyps or zooids. Suspension feeding permits capture of sperm for fertilization of ova that are retained by the parent. Distribution of broods among numerous small polyps, zooids, or other small modules facilitates supply of oxygen to embryos that are retained and protected by the parent. Brooding increases survival of offspring, controls dispersal, and can provide other developmental advantages. Colonial ascidians, pterobranch hemichordates, and entoprocts brood; most bryozoans and many colonial cnidarians brood. An unanswered question is why so many colonial anthozoans do not brood. Sponges share with colonies capacities for capturing sperm and separating numerous retained embryos yet many do not brood. Hypotheses for nonbrooding by colonies and sponges necessarily must apply to particular taxa. Few have been tested.
许多海洋殖民地动物通过在体内或体上孵化胚胎来照顾胚胎。为了发生孵化，动物的特征必须允许它发生，并且孵化必须至少与释放配子或受精卵一样有利。不同的殖民地孵化器的共同特征是悬浮喂养和由小模块组成的身体，这些小模块可以无限重复并且可以半自主地发挥作用，例如珊瑚虫或动物。悬浮喂养允许捕获精子，以便为父母保留的卵子受精。将幼虫分布在许多小珊瑚虫、动物或其他小模块中，有助于为父母保留和保护的胚胎提供氧气。孵化可以提高后代的存活率，控制扩散，并提供其他发育优势。海洋被囊动物、翼腕动物和内肛动物孵化；大多数苔藓动物和许多殖民地刺胞动物也孵化。一个悬而未决的问题是为什么如此多的殖民地珊瑚动物不孵化。海绵与殖民地一样具有捕获精子和分离多个保留胚胎的能力，但许多海绵不孵化。关于殖民地和海绵不孵化的假说必然适用于特定的分类群。这些假说很少得到检验。
