Neural architecture of Galathowenia oculata Zach, 1923 (Oweniidae, Annelida)

Rimskaya-Korsakova, N.; Kristof, A.; Malakhov, V.; Wanninger, A.

Авторы: Rimskaya-Korsakova NN, Kristof A., Malakhov VV, Wanninger A.
Журнал: Frontiers in Zoology
Том: 13
Номер: 5
Год издания: 2016
Издательство: BioMed Central
Местоположение издательства: London
Первая страница: 1
Последняя страница: 19
DOI: 10.1186/s12983-016-0136-2
Аннотация: Background: Oweniids are marine tubeworms burrowing in muddy sediments that in current phylogenies form anearly branching lineage within Annelida. Little is known about their general morphology, in particular the nervoussystem. Here we provide an immunocytochemical investigation of the nervous system of Galathowenia oculata inorder to discuss putative ancestral neuronal features in Oweniidae.Results: Adult Galathowenia oculata have neither a supraesophageal ganglion nor ganglia associated with theventral nerve cord. Instead, there is a dorsal brain commissure in the head collar that is engulfed by a cellularcortex. Accordingly, we herein term this neural structure “medullary brain commissure”. The anterior margin ofthe head collar exhibits numerous neurites that emerge from the brain commissure. The dorsolateral folds areinnervated by the ventrolateral neurite bundles extending from the circumesophageal connectives. In the anterioruniramous and biramous segments immunoreactive somata are distributed evenly along the ventral nerve cordand arranged metamerically in the posterior-most short segments. One dorsal and two pairs of lateral neuritebundles extend longitudinally along the body. Numerous serially arranged circular neurite bundles were labeled inanteriormost long segments. Metameric arrangement of the circular neurite bundles stained against FMRFamideand acetylated α-tubulin is revealed in posterior short segments. For the first time immunoreactive somataarranged in clusters are reported within the pygidium in oweniids.Conclusions: Due to the lack of head appendages and a sedentary mode of life, G. oculata exhibits a single dorsalcommissure (versus a brain with four commissures in most annelids). A “medullary brain commissure” is known sofar only in Oweniidae and Echiura. Lack of ganglia and metamery in the ventral nerve cord of the anteriormostsegments might be the result of the elongation of these segments. In the short posterior segments the metameryof immunoreactive somata and circular neurite bundles is conserved. We hypothesize that the unpaired ventral nervecord in adult oweniids might be a result of an initially paired ventral nerve cord that fuses during development, acondition not uncommon within Annelida.Keywords: Tubulin, Serotonin, FMRFamide, Medullary brain commissure, Medullary nerve cord, Single dorsalcommissure, Unpaired ventral nerve cord, Pygidial somata clusters, Dorsolateral folds
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Neural architecture of Galathowenia oculata Zach, 1923 (Oweniidae, Annelida)статья