Ostrovsky Andrew N, Dick Matthew H, Mawatari Shunsuke F
Department of Invertebrate Zoology, Faculty of Biology & Soil Science, St. Petersburg State University, Universitetskaja nab. 7/9, St. Petersburg 199034, Russia.
Zoolog Sci. 2007 Dec;24(12):1187-96. doi: 10.2108/zsj.24.1187.
We studied by SEM the external morphology of the ooecium in eight bryozoans of the genus Cauloramphus (Cheilostomata, Calloporidae): C. spinifer, C. variegatus, C. magnus, C. multiavicularia, C. tortilis, C. cryptoarmatus, C. niger, and C. multispinosus, and by sectioning and light microscopy the anatomy of the brooding apparatus of C. spinifer, C. cryptoarmatus, and C. niger. These species all have a brood sac, formed by invagination of the non-calcified distal body wall of the maternal zooid, located in the distal half of the maternal (egg-producing) autozooid, and a vestigial, maternally budded kenozooidal ooecium. The brood sac comprises a main chamber and a long passage (neck) opening externally independently of the introvert. The non-calcified portion of the maternal distal wall between the neck and tip of the zooidal operculum is involved in closing and opening the brood sac, and contains both musculature and a reduced sclerite that suggest homology with the ooecial vesicle of a hyperstomial ovicell. We interpret the brooding apparatus in Cauloramphus as a highly modified form of cheilostome hyperstomial ovicell, as both types share 1) a brood chamber bounded by 2) the ooecium and 3) a component of the distal wall of the maternal zooid. We discuss Cauloramphus as a hypothetical penultimate stage in ovicell reduction in calloporid bryozoans. We suggest that the internal-brooding genus Gontarella, of uncertain taxonomic affinities, is actually a calloporid and represents the ultimate stage in which no trace of the ooecium remains. Internal brooding apparently evolved several times independently within the Calloporidae.
我们通过扫描电子显微镜研究了Cauloramphus属（唇口目，Calloporidae科）8种苔藓虫的卵室外部形态：刺状Cauloramphus、杂色Cauloramphus、大型Cauloramphus、多房室Cauloramphus、扭曲Cauloramphus、隐铠Cauloramphus、黑色Cauloramphus和多刺Cauloramphus，并通过切片和光学显微镜研究了刺状Cauloramphus、隐铠Cauloramphus和黑色Cauloramphus的育幼器解剖结构。这些物种都有一个育幼囊，由母体个虫未钙化的远端体壁内陷形成，位于母体（产卵）自个虫的远端半部，还有一个退化的、由母体芽生的裸个虫卵室。育幼囊包括一个主室和一条独立于内缩部向外开口的长通道（颈部）。母体远端壁在颈部和个虫盖顶端之间的未钙化部分参与育幼囊的关闭和打开，并且含有肌肉组织和一个退化的骨片，这表明与高口卵胞的卵室囊泡具有同源性。我们将Cauloramphus的育幼器解释为唇口目高口卵胞的一种高度特化形式，因为这两种类型都具有1）一个由2）卵室和3）母体个虫远端壁的一个组成部分界定的育幼室。我们将Cauloramphus作为Calloporidae科苔藓虫卵胞退化的一个假设倒数第二阶段进行讨论。我们认为分类学亲缘关系不确定的内育型Gontarella属实际上是Calloporidae科的一个属，代表了卵室无残留痕迹的最终阶段。内育显然在Calloporidae科内独立进化了几次。
