Zanol J. Homology of prostomial and pharyngeal structures in Eunicida (Annelida) based on innervation and morphological similarities. Evol. 2a, 3a). In both species the anterior central nervous system (cns) consists of a ring-shaped brain surrounding the mouth opening and a ventral medullary cord (Figs. The ultra- thin sections were analyzed in a ZEISS EM10CR transmission electron microscope and documented on phosphor imaging plates (DITABIS) while semi- thin sections were documented using a light microscope (BX-51, Olympus). Neurites of the brain are arranged in parallel and are of different diameter (Figs. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Cell Tissue Res. The ventral nerve cord, is usually made up of a pair of cords that … Since Magelonidae also possess a pair of lateral medullary cords, arranged perpendicular to the brain [36], it is likely that two initially separated ventral medullary cords with non-segmental commissures, like in Owenia fusiformis, represent the primary condition. The size of the nerve cell somata is fairly uniform. In: Schmidt-Raesa A, Harzsch S, Purschke G, editors. Animals were relaxed in a 7% MgCl2 solution mixed with seawater 1:1 and then fixed in Bouin’s fluid (stock solution: 1 g Picrid acid solved in 100 ml Ethanol), (80 ml stock solution + 20 ml 35% Formol + 2 ml of Acetic acid) for 12 h, dehydrated in an ethanol series, followed by ethanol-butanol and butanol and preincubated in Histoplast (Thermo Scientific, Dreieich, Germany) at 60 °C. The brain neuropil (np) is located underneath the eye. Serial paraffin and semithin sections were analyzed with an Olympus microscope (BX-51) and photographed with an Olympus camera (Olympus cc12) equipped with the dot slide system (2.2 Olympus, Hamburg) and aligned using Imod [71] and Imod align (http://www.q-terra.de/biowelt/3drekon/guides/imod_first_aid.pdf). Sections were transferred to Xylol to elutriate Paraplast and were transferred from a Xylol-Ethanol (1:1) solution into a descending ethanol series (100, 95, 90, 80, 70% + nine drops of ammoniac to intensify the following reduction process, 40% ethanol). Meyer K, Bartolomaeus T. Ultrastructure and formation of the hooked setae in Owenia fusiformis delle Chiaje, 1842: implications for annelid phylogeny. Baskin D. The fine structure of neuroglia in the central nervous system of nereid polychaetes. "�,"V�-y,��.��2a/�^��p�'d�I�Q(�P�yp�]�K(�6��8n�C�Ndv�98�ӗm���CN\I�Ʉ&r\Ұ�M7��yx�);�.R�L�Yȗ��-�zA�җ�/���
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B gB. 1a. Other prominent ciliary structures exhibited by certain annelid taxa are ciliated grooves or papillae between neuro- and notopodia called lateral organs. In Oweniidae the brain is ring-shaped and confluent with two perpendicular arranged medullary cords which fuse posterior to a medio-ventrally located single medullary cord. Describes the structures of annelids and the functions of these features. Wanninger A. Mollusca: Bivalvia. Zoomorphology. c: Neurites contain lucent core (lc) as well as dense core (dc) vesicles. 2017;136:307–25. Zoomorphology. 1996;74:2143–53. 5a, d). For whole mount staining the tissue of Owenia fusiformis was permeabilized using 2% Triton X-100 in PBS for 65 h in the fridge. The value of this terminology was already doubted by Bullock and Horridge [3], since in most annelids these divisions are hardly or not discernible at all, especially in sedentary species [2, 3]. The four main branches of the tentacular crown are each innervated by two main nerves which are located in the lateral parts of the flat, leaf-like tentacles (Figs. are deposited in the Australian Museum, Sydney. Somata (so) of the nerve cells are intermingled between the epidermal cells. ... nervous systems and possess an enclosed circulatory system. Structure and Evolution of Invertebrate Nervous Systems. Purschke G. Sense organs in polychaetes (Annelida). The sections were again washed in distilled water and then stained in a silver nitrate solution before they were transferred to a 40 °C tempered reduction solution. Additional neuron types evolved in the stem lineage of Pleistoannelida+ Sipuncula/Amphinomidae [2, own unpublished observation]. 8c). While they are clearly visible in the nervous system they are not present in the epidermis. The neurites and often also the somata possess numerous vesicles that differ in stainability of their content. 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