Vendozoa and selective forces on animal origin and early diversification: reply to Dufour and McIlroy (2017).
Vendozoa and selective forces on animal origin and early diversification: reply to Dufour and McIlroy (2017).
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DOI：
10.1098/rstb.2017.0336
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发表时间：
2018-01-19
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影响因子：
--
通讯作者：
Cavalier-Smith T
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文献类型：
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作者：
Cavalier-Smith T
作者们强调，文多藻可能既包括以浮游生物为食的滤食性动物，也包括直接从其所处或活动的底层获取营养的动物，并认为硬表面和软表面可能提供了有利于不同体型的部分对比选择力的栖息地，这是正确的。然而，我的论文已经指出，一些文多藻是双面滤食叶状体，而另一些则可能是柔软表面上的水平居住者，它们可能通过腹侧非后囊细胞吞噬基质微生物，并通过后囊细胞吞噬浮游生物。比Dufour和McIlroy [1]更好的解释Fractofusus可能是它只是这样一个背领细胞和腹侧基质饲养者;如果是这样，它是一个presponge，而不是一个pre-placozoan。如果埃迪卡拉纪生物存在这种双重摄食模式，那么浮游生物和底栖生物之间的分歧就不像它们所暗示的那样尖锐。他们的评论提出了七个问题：（i）概念上，“preplacozoan等级的组织”如何真正不同于presponge。(ii)我们能从化石中可靠地推断出文多动物的实际进食方式和不同的细胞类型吗？(iii)文氏动物门、海绵动物门和扁平动物门之间的系统发育关系是什么？以及在每个分支点之前推断出的表型？(iv)什么是vendozoon，海绵和两侧起源的相对时间？(v)基质喂养是否提供了一个过渡到第一个动物的似是而非的后领鞭毛虫到presponge路径？(vi)什么样的选择力对神经系统的起源至关重要？(vii)要想很好地解释主要的进化转变，需要什么？
The authors are right to emphasize that Vendozoa probably include both filter feeders on plankton and those deriving nutrition directly from the underlying substratum on which they lie or move and to argue that hard and soft surfaces would have provided habitats offering partially contrasting selective forces favouring distinct body forms. However, my paper already argued that some Vendozoa were bifacial filter-feeding fronds and others likely to have been horizontal dwellers on soft surfaces that may have fed phagocytically on substrate microrganisms by ventral non-choanocyte cells and dorsally on plankton by choanocytes. A better interpretation of Fractofusus than that of Dufour & McIlroy [1] might be that it was just such a dorsal collar-cell and ventral substrate feeder; if so it was a presponge, not a pre-placozoan. If Ediacaran organisms of that dual feeding mode existed, the dichotomy between plankton feeders and substrate feeders was less sharp than they imply. Their comment raises seven issues:(i) conceptually, how does the ‘preplacozoan grade of organization’really differ from a presponge.(ii) Can we reliably infer from fossils the actual feeding mode and different cell types of Vendozoa?(iii) What are the phylogenetic relationships between Vendozoa, sponges and Placozoa; and the inferred phenotypes prior to each branch point?(iv) What is the relative timing of vendozoan, sponge and bilaterian origins?(v) Does substrate feeding offer a transition to the first animal as plausible as the choanoflagellate to presponge path?(vi) What selective force was crucial for the origin of the nervous system?(vii) What is required for good explanations of major evolutionary transitions?
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