Structure of the nervous system in Tubiluchus troglodytes (Priapulida)

Abstract

Abstract. The nervous system of the meiobenthic priapulid species Tubiluchus troglodytes is described by immunohistochemistry and confocal laser scanning microscopy. The brain is circumpharyngeal, consisting of a central ring of neuropil and both anterior and posterior somata. From the brain emerges a ventral nerve cord, which shows ganglion‐like swellings in the neck and caudal region. The introvert includes longitudinal neurite bundles running below and between the rows of scalids, with a small cluster of sensory cells under each scalid. In the body wall of the neck and trunk region, longitudinal and circular neurite bundles are present in an orthogonal pattern. The tail is innervated from the caudal swelling of the ventral nerve cord; it also includes longitudinal and circular bundles in an orthogonal pattern. The pharynx has a reticulated system of neurite bundles running between the pharyngeal teeth and fimbrillae. Below each tooth and fimbrilus is a ganglion‐like cluster of somata. The intestine is surrounded by a nerve net. The data on the nervous system are compared within other priapulids and with other species of Scalidophora (Kinorhyncha and Loricifera).

The neuromuscular system of Pycnophyes kielensis (Kinorhyncha: Allomalorhagida) investigated by confocal laser scanning microscopy

“…More data are available for priapulids, which have also been investigated by use of immunocytochemistry [41, 80]. Adults of the meiobenthic Tubiluchus troglodytes show an intraepidermal nervous system with a circumpharyngeal brain that like in kinorhynchs consists of a central ring of neuropil and both anterior and posterior somata [80].…”

“…Adults of the meiobenthic Tubiluchus troglodytes show an intraepidermal nervous system with a circumpharyngeal brain that like in kinorhynchs consists of a central ring of neuropil and both anterior and posterior somata [80]. From the brain emerges an unpaired ventral nerve cord with ganglion like swellings in the neck and caudal region [80]. Longitudinal neurite bundles are running below and between the rows of scalids, and a small cluster of sensory cells is present under each scalid [80].…”

“…From the brain emerges an unpaired ventral nerve cord with ganglion like swellings in the neck and caudal region [80]. Longitudinal neurite bundles are running below and between the rows of scalids, and a small cluster of sensory cells is present under each scalid [80]. In contrast to kinorhynchs, the priapulid body wall of the neck and trunk region contains a net of longitudinal and circular neurite bundles that are present in an orthogonal pattern [80].…”

“…Longitudinal neurite bundles are running below and between the rows of scalids, and a small cluster of sensory cells is present under each scalid [80]. In contrast to kinorhynchs, the priapulid body wall of the neck and trunk region contains a net of longitudinal and circular neurite bundles that are present in an orthogonal pattern [80]. The intestine is surrounded by a nerve net, and the caudal appendage is innervated from a caudal swelling of the ventral nerve cord and also includes longitudinal and circular nerve bundles in an orthogonal pattern [80].…”

Fuxianhuiid ventral nerve cord and early nervous system evolution in Panarthropoda

“…2 B-E) is recognized as an ancestral condition that persisted in derived members of upper stem-group Euarthropoda (SI Text). Among extant groups, homologs of the intersegmental peripheral nerves are expressed in both Priapulida (31) and Onychophora (12,13,15,29) but are otherwise greatly reduced in number or completely lost in crown-group Euarthropoda and Tardigrada, respectively (1,5,16,28) (Fig. S5); the secondary reduction/loss is recognized as a result of parallel evolution between these lineages.…”