Cnidarian Larvae: True Planulae, Other-Than-Planulae, and Planulae That Don’t Look Like Planulae

Pub Date : 2023-12-01 DOI:10.1134/s1062360423070044

引用次数: 0

Abstract

The life cycle of the common ancestor of Metazoa is a widely debated topic in EvoDevo. This is intimately linked to a number of questions, such as how the larva appeared in the metazoan life cycle and which larval form can be considered ancestral. To approach these questions, we can analyse the life cycles and larval forms of Cnidaria, the basal metazoans that form a sister group to the Bilateria. Almost all cnidarians have a pelagic larva in their life cycle. These larvae are commonly referred to as “planula,” with few exceptions. The planula is a ciliated lecithotrophic larva with epithelial ectoderm and endoderm, a gastric cavity, and an elongated body. The review examines whether the larvae of various Cnidaria fit this description and explores which larval form is ancestral for different cnidarian taxa. It also highlights the enormous diversity of cnidarian larvae, which is still underestimated, and infers the relationship between the evolution of life cycles, reproductive patterns, and larval forms in various phylogenetic groups of cnidarians.

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刺丝胞幼体：真正的浮游动物、非浮游动物和看起来不像浮游动物的浮游动物

摘要元古动物共同祖先的生命周期是进化论中一个广受争议的话题。这与许多问题密切相关，如幼虫是如何出现在元古宙的生命周期中，以及哪种幼虫形式可被视为祖先。为了探讨这些问题，我们可以分析网囊动物的生命周期和幼虫形态，网囊动物是基础元古动物，与双鞭毛目动物是姊妹类群。几乎所有的刺胞动物在其生命周期中都有一个浮游幼虫。这些幼虫通常被称为 "刨虫"，只有少数例外。栉水母是一种纤毛卵磷脂营养幼虫，具有上皮外胚层和内胚层、胃腔和拉长的身体。这篇综述研究了各种刺胞动物的幼虫是否符合这一描述，并探讨了不同刺胞动物类群的幼虫祖先形态。该综述还强调了刺胞动物幼虫的巨大多样性--这种多样性仍被低估，并推断了刺胞动物各系统发育类群中生命周期、繁殖模式和幼虫形态进化之间的关系。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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