Affiliation:
1. Far Eastern Branch, Russian Academy of Sciences, A.V. Zhirmunsky National Scientific Center of Marine Biology, Vladivostok, Russia
2. Department of Biology, Virginia Commonwealth University, Richmond, VA, USA
Abstract
The fine structure of mature pseudocnidae of 32 species of nemerteans, representatives of 20 genera, six families, and two classes was investigated with scanning and transmission electron microscopy. Pseudocnidae are composed of four layers (cortex, medulla, precore layer, and core) in most species investigated, but the degree of development and position of each layer can vary between different species. The secretion products comprising immature pseudocnidae segregate into separate layers: a thin envelope, which subsequently separates into the cortex and medulla and an extensive internal layer. We distinguish two pseudocnida types: type I is characterized by a two-layered core and type II by a three-layered core. Type I pseudocnidae are present in archinemertean species, Carinoma mutabilis, and in all pilidiophoran species, except Heteronemertea sp. 5DS; type II pseudocnidae occur in all studied species of Tubulanidae and the basal Heteronemertea sp. 5DS. Based on the structure of the discharged pseudocnidae observed in eleven species of palaeonemerteans and in eight species of pilidiophorans, we distinguish three different mechanisms (1–3) of core extrusion/discharge with the following characteristics and distribution: (1) the outer core layer is everted simultaneously with the tube-like layer and occurs in type I pseudocnidae of most species; (2) the extruded core is formed by both eversion of the outer core layer and medullar layer, and occurs in type I pseudocnidae of Micrura cf. bella; (3) the eversion of the outer core layer begins together with the core rod and core rod lamina and occurs in type II pseudocnidae. Morpho-functional comparison with other extrusomes (cnidae, sagittocysts, rhabdtites, and paracnids) confirm that pseudocnidae are homologous structures that are unique to nemerteans.
Funder
Russian Foundation for Basic Research
Ministry of Science and Higher Education, Russian Federation
Subject
General Agricultural and Biological Sciences,General Biochemistry, Genetics and Molecular Biology,General Medicine,General Neuroscience
Reference62 articles.
1. A non-sulfated chondroitin stabilizes membrane tubulation in cnidarian organelles;Adamczyk;Journal of Biological Chemistry,2010
2. Aportaciones a la estructura y ultraestructura de heteronemertinos (Segunda parte);Anadón;Boletín de la Real Sociedad Española de Historia Natural/Sección Biológica,1976
3. A transcriptomic approach to ribbon worm systematics (nemertea): resolving the pilidiophora problem;Andrade;Molecular Biology and Evolution,2014
4. The nematocyst: a molecular map of the cnidarian stinging organelle;Beckmann;International Journal of Developmental Biology,2012
5. A fast recoiling silk-like elastomer facilitates nanosecond nematocyst discharge;Beckmann;BMC Biology,2015
Cited by
7 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献