Larval Development of Two N. E. Pacific Pilidiophoran Nemerteans (Heteronemertea; Lineidae)
Larval Development of Two N. E. Pacific Pilidiophoran Nemerteans (Heteronemertea; Lineidae)
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DOI：
10.1086/bblv229n3p265
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发表时间：
2015-12-01
影响因子：
1.6
通讯作者：
Maslakova, Svetlana A.
中科院分区：
文献类型：
--
作者：
Hiebert, Terra C.;Maslakova, Svetlana A.
在纽形动物门中，纤毛虫是唯一的，它是纽形动物中的一个类群--纤毛虫属（Pilidiophora）中发现的一种明显的寄生幼虫。在纤毛器内，幼虫从幼虫体内的一系列表皮内陷发育而成，称为成虫盘。在浮游生物中，这些圆盘在幼虫的肠道周围生长并融合，持续数周至数月。一旦完成，幼虫在灾难性的变态中从幼虫身上挣脱出来，并经常将幼虫作为第一餐。三分之一的纽形动物物种被认为会产生纤毛，但已知的幼虫只有极少数物种;从受精到变态的发育只在一个物种中描述过，阿拉斯加微虫。已知的纤毛体包括滋养型和滋养型两种形式，并且在其他方面表现出巨大的形态多样性。在这里，我们描述了两个线状物种的完整发展，是共同的东北太平洋沿岸，Micrura wilsoni和Lineus sp。这两个物种都具有典型的帽状营养纤毛，成虫盘的出现顺序与M.阿拉斯加。“红色”的Lineus sp.的毛状体类似于其他几个物种的毛状体，如Lineus flavescens，并可能具有pilidiophoran分支的特征。M. wilsoni有相对透明的卵母细胞和一个似乎是独特的色素沉着模式的纤毛。这两个物种的成年人更常见于潮间带比他们的幼虫在浮游生物。
Unique to the phylum Nemertea, the pilidium is an unmistakable planktonic larva found in one group of nemerteans, the Pilidiophora. Inside the pilidium, the juvenile develops from a series of epidermal invaginations in the larval body, called imaginal discs. The discs grow and fuse around the larval gut over the course of weeks to months in the plankton. Once complete, the juvenile breaks free from the larval body in a catastrophic metamorphosis, and often devours the larva as its first meal. One third of nemertean species are expected to produce a pilidium, but the larvae are known for very few species; development from fertilization to metamorphosis has been described in only one species, Micrura alaskensis. Known pilidia include both planktotrophic and lecithotrophic forms, and otherwise exhibit great morphological diversity. Here, we describe the complete development in two lineiform species that are common to the northeast Pacific coast, Micrura wilsoni and Lineus sp. "red." Both species possess typical, cap-shaped planktotrophic pilidia, and the order of emergence of imaginal discs is similar to that which is described in M. alaskensis. The pilidium of Lineus sp. "red" resembles pilidia of several other species, such as Lineus flavescens, and potentially characterizes a pilidiophoran clade. M. wilsoni has relatively transparent oocytes and a pilidium with what appears to be a unique pattern of pigmentation. The adults of both species are more commonly observed in intertidal zones than their larvae are in the plankton.