Development of a lecithotrophic pilidium larva illustrates convergent evolution of trochophore-like morphology

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• 作者：Marie K. Hunt ; Svetlana A. Maslakova
• 关键词：Pilidium ; Trochophore ; Convergence ; Nemertea ; Larva ; Marine invertebrate ; Development ; Imaginal discs ; Lecithotrophy
• 刊名：Frontiers in Zoology
• 出版年：2017
• 出版时间：December 2017
• 年：2017
• 卷：14
• 期：1
• 全文大小：8254KB
• 刊物主题：Zoology; Applied Ecology; Biodiversity; Animal Physiology;
• 出版者：BioMed Central
• ISSN：1742-9994
• 卷排序：14

文摘

BackgroundThe pilidium larva is an idiosyncrasy defining one clade of marine invertebrates, the Pilidiophora (Nemertea, Spiralia). Uniquely, in pilidial development, the juvenile worm forms from a series of isolated rudiments called imaginal discs, then erupts through and devours the larval body during catastrophic metamorphosis. A typical pilidium is planktotrophic and looks like a hat with earflaps, but pilidial diversity is much broader and includes several types of non-feeding pilidia. One of the most intriguing recently discovered types is the lecithotrophic pilidium nielseni of an undescribed species, Micrura sp. “dark” (Lineidae, Heteronemertea, Pilidiophora). The egg-shaped pilidium nielseni bears two transverse circumferential ciliary bands evoking the prototroch and telotroch of the trochophore larva found in some other spiralian phyla (e.g. annelids), but undergoes catastrophic metamorphosis similar to that of other pilidia. While it is clear that the resemblance to the trochophore is convergent, it is not clear how pilidium nielseni acquired this striking morphological similarity.