Structure of the oral tentacles of early ontogeny stage in brachiopod Hemithiris psittacea (Rhynchonelliformea, Rhynchonellida)

IF 1.5 4区 医学 Q2 ANATOMY & MORPHOLOGY
Tatyana Valerievna Kuzmina, Elena Nikolaevna Temereva
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引用次数: 0

Abstract

Brachiopods have the most complex lophophore in comparison with other lophophorates, i.e., phoronids and bryozoans. However, at early ontogenetic stages, brachiopods have a lophophore of simple morphology, which consists of the oral tentacles. Data on the ultrastructure of the oral tentacles is mostly missing. Nonetheless, it has recently been suggested that the structure of oral tentacles is ancestral for all lophophorates in general, and for brachiopods in particular. The fine structure of the oral tentacles in the brachiopod Hemithiris psittacea is studied using light microscopy, transmission and scanning electron microscopy, cytochemistry and confocal laser scanning microscopy. The oral tentacles have a round shape in transverse section, and four ciliary zones, i.e., one frontal, two lateral, and one abfrontal. Latero-frontal sensory cells occur among the frontal epithelium. Four basiepithelial nerves in the ciliary epithelium are colocalized with ciliary zones. Lophophores of simple morphology in phoronids and brachiopods are characterized by non-specified round forms of tentacles. In phoronids and bryozoans, tentacles have additional latero-frontal ciliary zones that function as a sieve during filtration. In most brachiopods, lateral cilia are involved in the capture of food particles, whereas latero-frontal cells are retained in the frontal zone as sensory elements. The oral tentacles of H. psittacea contain a coelomic canal and have distinct frontal and abfrontal longitudinal muscles, which are separated from each other by peritoneal cells. A similar structure of tentacle muscles occurs in all bryozoans, whereas in phoronids, the frontal and abfrontal tentacle muscles are not separated by peritoneal cells. We suggest that the lophophorates' ancestor had tentacles, which were similar to the tentacles of some phoronids with lophophore of simple morphology. We also assume that the structure of the oral tentacles is ancestral for all brachiopods and the specialization of brachiopod tentacles correlates with the appearance of the double row of tentacles.

Abstract Image

腕足动物 Hemithiris psittacea (Rhynchonelliformea, Rhynchonellida) 早期发育阶段口腔触手的结构
腕足动物的嗜食器与其他嗜食器动物(即噬龙类和岩龙类)相比最为复杂。然而,在腕足动物的早期发育阶段,它们的嗜食器形态简单,由口腔触手组成。口触手的超微结构数据大多缺失。尽管如此,最近有人提出,口触手的结构是所有嗜食性动物,特别是腕足动物的祖先结构。本文利用光学显微镜、透射和扫描电子显微镜、细胞化学和激光共聚焦扫描显微镜研究了腕足动物Hemithiris psittacea的口腔触手的精细结构。口触手的横切面呈圆形,有四个纤毛区,即一个正面区、两个侧面区和一个背面区。额叶上皮细胞中有侧额感觉细胞。睫状上皮中的四条基底上皮神经与睫状区位于同一位置。在噬龙类和腕足动物中,形态简单的嗜食性触手的特点是触手呈不规则的圆形。在噬龙类和腕足动物中,触手具有额外的侧额纤毛区,在过滤过程中起到筛网的作用。在大多数腕足动物中,侧纤毛参与捕捉食物颗粒,而额侧细胞则作为感觉元件保留在额区。鹦鹉螺的口触手包含一个腹腔管,并有明显的额部和腹部纵向肌肉,这些肌肉之间由腹膜细胞隔开。所有双壳类动物都有类似的触手肌肉结构,而在噬龙目动物中,额部和腹部触手肌肉没有被腹膜细胞分开。我们认为,噬孔动物的祖先具有触手,这种触手与一些具有简单形态噬孔动物的触手相似。我们还假定,口触手的结构是所有腕足动物的祖先结构,腕足动物触手的特化与双排触手的出现有关。
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来源期刊
Journal of Morphology
Journal of Morphology 医学-解剖学与形态学
CiteScore
2.80
自引率
6.70%
发文量
119
审稿时长
1 months
期刊介绍: The Journal of Morphology welcomes articles of original research in cytology, protozoology, embryology, and general morphology. Articles generally should not exceed 35 printed pages. Preliminary notices or articles of a purely descriptive morphological or taxonomic nature are not included. No paper which has already been published will be accepted, nor will simultaneous publications elsewhere be allowed. The Journal of Morphology publishes research in functional, comparative, evolutionary and developmental morphology from vertebrates and invertebrates. Human and veterinary anatomy or paleontology are considered when an explicit connection to neontological animal morphology is presented, and the paper contains relevant information for the community of animal morphologists. Based on our long tradition, we continue to seek publishing the best papers in animal morphology.
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