Purschke Günter
Spezielle Zoologie, Fachbereich 5, Universität Osnabrück, Barbarastraße 11, W-4500 Osnabrück, Federal Republic of Germany.
J Morphol. 1992 Jan;211(1):7-21. doi: 10.1002/jmor.1052110103.
In addition to the pigmented ocelli, four different types of photoreceptor-like organs without shading pigment have been found in Saccocirrus papillocercus and S. krusadensis. The sensory cells of these presumed ocelli are either ciliary or rhabdomeric with ciliary rudiments. With the exception of the multicellular type-2 ocelli they are bicellular consisting of a sensory cell and a supportive cell. In each ocellus the supportive cell forms a thin cup-shaped envelope around the sensory elements. In the type-2 ocellus, 7 supportive cells form an ovoid cavity leaving openings through which dendritic processes of an equal number of sensory cells enter the cavity. The pigmented ocelli possess an ocellar cavity communicating with the exterior through a pore in the eyecup, ciliary rudiments in both sensory and supportive cell, and additional non-photoreceptive sensory cells in the opening of the eyecup. The sensory organs show characteristic differences between the two species, such as presence or absence of a particular type of ocellus (type 2 is absent in S. krusadensis, type 3 in S. papillocercus), number of cilia in type-4 ocelli, density of microvilli, number of non-photoreceptive sensory cells in the pore of the pigmented ocellus, etc. These differences provide important characters which can be used for discrimination either of species or of subgeneric taxa in Saccocirrus. The phylogenetic significance of the different photoreceptive organs is discussed.
除了色素眼点外，在乳头尾帚虫（Saccocirrus papillocercus）和克鲁萨德尾帚虫（S. krusadensis）中还发现了四种不同类型的无遮光色素的光感受器样器官。这些假定眼点的感觉细胞要么是具纤毛的，要么是具有纤毛原基的微绒毛状的。除了多细胞的2型眼点外，它们都是双细胞的，由一个感觉细胞和一个支持细胞组成。在每个眼点中，支持细胞围绕感觉元件形成一个薄的杯状包膜。在2型眼点中，7个支持细胞形成一个卵形腔，有开口，相同数量的感觉细胞的树突状突起通过这些开口进入腔内。色素眼点具有一个通过眼杯上的孔与外部相通的眼腔、感觉细胞和支持细胞中的纤毛原基，以及眼杯开口处额外的非光感受性感觉细胞。这两种物种的感觉器官表现出特征性差异，例如特定类型眼点的有无（克鲁萨德尾帚虫中没有2型眼点，乳头尾帚虫中没有3型眼点）、4型眼点中的纤毛数量、微绒毛密度、色素眼点孔中的非光感受性感觉细胞数量等。这些差异提供了重要特征，可用于区分尾帚虫属中的物种或亚属分类单元。文中讨论了不同光感受器器官的系统发育意义。
