| 摘要: |
| 苔藓动物的群体是由生理上互相连系、以无性繁殖方法复制的称之为个虫的成员组成。幼虫变态后，绝大多数苔藓虫形成构成群体基础的单一个虫，称为初虫，这些单一的初虫通常为一摄食个虫，有时则为形态多样的无摄食功能的空个虫；另一些幼虫变态后则形成2个、3个或5个个虫，称之为初虫群，初虫群的每一个体均为摄食个虫。绝大多数苔藓虫群体都由单一的初虫或初虫群以无性出芽而成，只有极少数苔藓虫群体由休眠芽产生或由裂殖方式产生。按照苔藓动物学关于群体性质的一般概念，每一群体由若干类型的个虫和多个虫部分构成，而某些群体还包括个虫外部分。个虫是无性繁殖产生、分别执行如摄食、生殖、支撑、保护等主要生理或结构功能的自然连系的形态单位。多个虫部分包括既存个虫界限外面生长的连续体壁层及其包裹的体腔，随着群体发育，它们便成为个虫之一部分。个虫外部分在群体整个生命期间都位于个虫界限之外，包括体壁(有骨骼层或无骨骼层)、非体壁之一部分的骨骼以及相邻的体腔。群体是一个可与单体动物相比拟而与环境相互作用的完整生命机体，一般说来，群体是均匀一致的。组成群体的成员除初虫或初虫群是以有性生殖方式产生外，所有其他部分都是由细胞生理上连续的有丝分裂和非细胞部分的分泌作用产生的。如果假定它们的基因是均匀性的，那么就可以说在一群体内的个虫在形态上是同一的，然而一苔藓动物群体内的个虫在某些特征上通常是不同的。一群体内表征上不同的个虫表达了那些未必反映基因差异的形态变异，任一群体所显示的这种非遗传变异都可归于下述诱发群体内形态变异的四个非遗传因素:个虫和个虫外结构的个体发育、群体发育(或群育)、多形结构和微环境。 |
| 关键词: 唇口目苔藓虫、早期发育、软壁亚目膜孔苔虫科、琥珀苔虫科 |
| DOI： |
| 分类号: |
| 基金项目:中国科学院海洋研究所调查研究报告第3159号。
国家自然科学基金资助项目(No.39670100)和中国科学院生物区系特别支持费资助项目。 |
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| SIGNIFICANCE OF EARLY ASTOGENY OF CHEILOSTOME BRYOZOANS IN THEIR EVOLUTION Ⅰ. THE CHARACTERISTICS OF EARLY ASTOGENY OF SUBORDER MALACOSTEGINA (MEMBRANIPORIDAE AND ELECTRIDAE), WITH DESCRIPTIONS OF A NEW GENUS AND SIX NEW SPECIES |
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Liu Xixing, Yin Xueming, Xia Wa
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Institute of Oceanology, Chinese Academy of Sciences
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| Abstract: |
| It is well known that, even a simple colony in the primitive cheilostome bryozoans (such as Membraniporid and Electrid forms) is composed of two zones: a primary zone of astogenetic change and a primary zone of ontogenetic repetition. Within a colony, ontogenetic changes in morphology are recognizable along a gradient proximally from the growing margin and astogenetic changes in morphology are expressed on a gradient distally from the ancestrula. Therefore, morphological variations within a colony are usually recognizable and used often as the characters by which different taxa are distinguished from one another. The ancestrula or ancestrular group formed after metamorphosis of the larvae may be similar to the subsequently formed zooids in morphological details.
Although there is controversy on the taxonomic and phylogenetic significance of the ancestrula and early astogeny of cheilostome bryozoans have been discussed, the authors try their best to address the subject on the basis of the abundant data on ancestrula and early astogeny found in about 300 species of suborders Malacostegina, Neocheilostomina (infraorders Pseudomalacostegomorpha, Cellulariomorpha and Cryptocystomorpha) and Ascophorina (infraorders Cribriomorpha, Hippothoomotpha, Umbonulomorpha and Lepraliomorpha), and attemp to reveal their morphological series in order to extract some information about the mode of evolution supportive of the phylolenetic development of Cheilostome Bryozoans.
This paper is a theses on the subject 《Significance of Early Astogeny of Cheilostome Bryozoans in their Evolution》, deals with the early astogeny of suborder Malacostegina (Families Membraniporidae and Flustridae), and includes descriptions of a new genus and six new species. |
| Key words: cheilostome bryozoans,early astogeny,MEMBRANIPORIDAE ,ELECTRIDAE |
