Correction to 'Origin of animal multicellularity: precursors, causes, consequences-the choanoflagellate/sponge transition, neurogenesis and the Cambrian explosion'
Correction to 'Origin of animal multicellularity: precursors, causes, consequences-the choanoflagellate/sponge transition, neurogenesis and the Cambrian explosion'
复制标题
对“动物多细胞性的起源：前体、原因、后果——领鞭毛虫/海绵转变、神经发生和寒武纪爆发”的更正
DOI：
10.1098/rstb.2017.0001
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Cavalier-Smith T
中科院分区：
文献类型：
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作者：
Cavalier-Smith T
进化成多细胞是很容易的，尤其是光养生物和渗透养生物，它们的多细胞像单细胞一样进食。进化的动物要难得多，也独特得多；可能只有通过底栖“植虫动物”和上层纤毛幼虫的一条途径，才能实现从吞噬原生动物到具有肠道的动物的营养连续性。鞭藻原生动物产生海绵。将介导幼虫沉淀的海绵烧瓶细胞转化为由突触控制的线虫囊，可能产生了刺胞菌。我用海绵/腔肠动物/双边途径取代了海克尔的胃理论：盘虫、水螅虫和栉水母是次要的；茎珊瑚虫的发育突变可以独立地产生体腔动物双边虫和栉水母。我强调动物起源的概念性方面（选择性、发展性），涉及摄食方式、细胞结构、相关原生动物的系统发育、序列证据、生态学和古生物学。上皮和结缔组织只能通过补偿显著降低的摄食效率而进化为非胆管细胞。因此，更大的身体能够过滤更多的水，为细菌提供食物，并为光合细菌提供庇护，两者加起来比细胞分化所牺牲的食物更多。一种假想的无根三胚层海绵（夹在两个卵母细胞上皮之间的结缔组织）通过选择更大的分散纤毛幼虫来加速底栖动物的营养能力和过度生长的原生动物竞争，从而进化出卵制。已灭绝的Vendozoa可能是在多孔水通道和刺胞肠道/刺丝囊/突触进化之前，具有含卵母细胞上皮的这种生物级别的精化。本文是“基因组学时代的进化和形态多样性的起源”主题的一部分。
Evolving multicellularity is easy, especially in phototrophs and osmotrophs whose multicells feed like unicells. Evolving animals was much harder and unique; probably only one pathway via benthic ‘zoophytes’ with pelagic ciliated larvae allowed trophic continuity from phagocytic protozoa to gut-endowed animals. Choanoflagellate protozoa produced sponges. Converting sponge flask cells mediating larval settling to synaptically controlled nematocysts arguably made Cnidaria. I replace Haeckel's gastraea theory by a sponge/coelenterate/bilaterian pathway: Placozoa, hydrozoan diploblasty and ctenophores were secondary; stem anthozoan developmental mutations arguably independently generated coelomate bilateria and ctenophores. I emphasize animal origin's conceptual aspects (selective, developmental) related to feeding modes, cell structure, phylogeny of related protozoa, sequence evidence, ecology and palaeontology. Epithelia and connective tissue could evolve only by compensating for dramatically lower feeding efficiency that differentiation into non-choanocytes entails. Consequentially, larger bodies enabled filtering more water for bacterial food and harbouring photosynthetic bacteria, together adding more food than cell differentiation sacrificed. A hypothetical presponge of sessile triploblastic sheets (connective tissue sandwiched between two choanocyte epithelia) evolved oogamy through selection for larger dispersive ciliated larvae to accelerate benthic trophic competence and overgrowing protozoan competitors. Extinct Vendozoa might be elaborations of this organismal grade with choanocyte-bearing epithelia, before poriferan water channels and cnidarian gut/nematocysts/synapses evolved.This article is part of the themed issue ‘Evo-devo in the genomics era, and the origins of morphological diversity’.