TY - CONF

T1 - Diversity of nervous system patterns in the earliest bilaterians, Nemertodermatida and Acoela

AU - Райкова, Ольга Игоревна

AU - Meyer-Wachsmuth, Inga

AU - Jondelius, Ulf

N1 - Conference code: 4

PY - 2017

Y1 - 2017

N2 - The early steps of nervous system (NS) evolution in Bilateria still remain enigmatic. Nemertodermatida are microscopic marine worms that together with Acoela and Xenoturbellida form the Xenacoelomorpha, sister group of all other bilaterian animals. Nemertodermatid morphology is generally less derived than that of Acoela. The NS patterns in four nemertodermatid species were investigated by confocal microscopy and immunohistochemistry with anti-tubulin, anti-5-HT and anti-FMRFamide antibodies.The NS of Flagellophora is composed of a large neuropile and a loose brain with nerve fibres innervating the frontal broom organ. Sterreria shows a concentrated commissural-like brain similar to acoels. Nemertoderma has a basiepidermal brain ring and a pair of ventro-lateral neurite bundles. Meara has no brain but only of a pair of basiepidermal lateral neurite bundles. The innervation of the gut in Nemertodermatida is apparently absent similar to the condition in Xenoturbella. Thus the hypothetic ancestor of Nemertodermatida likely had an almost cnidarian-grade NS with no brain and no stomatogastric NS.Within Xenacoelomorpha, Xenoturbella has a cnidarian-grade basiepidermal NS with no centralisation. The NS of Nemertodermatida displays considerable plasticity. In acoels, the NS evolution occurs not in the Acoela as a whole, but takes place independently in various smaller monophyletic acoel branches (i.e. species of one genus). There is parallel evolution of a deep-lying concentrated dorsal brain starting from an ancestral loose surface network-like brain. The study was supported by ZIN RAS (NIOKTR: АААА-А17-117030110029-3), RFBR 16-04-00593 and 15–29–02650.

AB - The early steps of nervous system (NS) evolution in Bilateria still remain enigmatic. Nemertodermatida are microscopic marine worms that together with Acoela and Xenoturbellida form the Xenacoelomorpha, sister group of all other bilaterian animals. Nemertodermatid morphology is generally less derived than that of Acoela. The NS patterns in four nemertodermatid species were investigated by confocal microscopy and immunohistochemistry with anti-tubulin, anti-5-HT and anti-FMRFamide antibodies.The NS of Flagellophora is composed of a large neuropile and a loose brain with nerve fibres innervating the frontal broom organ. Sterreria shows a concentrated commissural-like brain similar to acoels. Nemertoderma has a basiepidermal brain ring and a pair of ventro-lateral neurite bundles. Meara has no brain but only of a pair of basiepidermal lateral neurite bundles. The innervation of the gut in Nemertodermatida is apparently absent similar to the condition in Xenoturbella. Thus the hypothetic ancestor of Nemertodermatida likely had an almost cnidarian-grade NS with no brain and no stomatogastric NS.Within Xenacoelomorpha, Xenoturbella has a cnidarian-grade basiepidermal NS with no centralisation. The NS of Nemertodermatida displays considerable plasticity. In acoels, the NS evolution occurs not in the Acoela as a whole, but takes place independently in various smaller monophyletic acoel branches (i.e. species of one genus). There is parallel evolution of a deep-lying concentrated dorsal brain starting from an ancestral loose surface network-like brain. The study was supported by ZIN RAS (NIOKTR: АААА-А17-117030110029-3), RFBR 16-04-00593 and 15–29–02650.

M3 - Abstract

SP - 47

T2 - 4th International Congress on Invertebrate Morphology

Y2 - 18 August 2017 through 23 August 2017

ER -