Rastrognathia macrostoma, Kristensen & Norrevang, 1977

Gąsiorowski, Ludwik, Bekkouche, Nicolas & Worsaae, Katrine, 2017, Morphology and evolution of the nervous system in Gnathostomulida (Gnathifera, Spiralia), Organisms Diversity & Evolution (New York, N. Y.) 17 (2), pp. 447-475 : 458-460

Rastrognathia macrostoma

SLIR and TyrTLIR nervous structures as well as DAPIstained cell nuclei are visualized with CLSM The brain consists of the central neuropil (np, Figs. 7f, 8d) surrounded by perikarya and sensory structures (Figs. 7d–f, 8b–d). The SLI reactivity was detected in six brain cells (2 × dp, 2 × mp, 2 × lp, Figs. 7d, 8b) and two ventral brain commissures (vac and vpc, Figs. 7b, 8c) forming a ring-shaped structure. In addition, a distinct dorso-anterior TyrTLIR commissure was visualized (dac, Figs. 7e, 8d).

Three pairs of longitudinal SLIR and TyrTLIR nerve cords extend from the brain to the posterior commissure: ventro-lateral, lateral, and dorso-lateral (vlc, lc, dc, Figs. 7a–c, e, f; 8); the two former are interconnected by a fine neurite in the anterior part of the trunk. A pair of peripheral SLIR anterior perikarya (ap, Figs. 7a, b; 8a, c) projects neurites into the ventro-lateral nerve cords anterior to the pharynx, and a single middorsal TyrTLIR perikaryon (mdc, Figs, 7c, 8e) is located above the male genital opening. A few ciliary gut receptors occur along the midventral line (cgr, Fig. 5c, f).

The stomatogastric nervous system consists of a buccal ganglion (bg, Fig. 8d ) with about 20 perikarya and a pair of buccal nerves (bn, Fig. 8d ) extending along the pharyngeal bulb, both being TyrTLIR.

The rostral TyrTLIR sensory structures include three apical ventral ciliary organs (vco, Figs. 7e, f; 8d), four pairs of compound cirri (cc, Fig. 7e, f, one pair shown in Fig. 8d ), and three pairs of spiral organs, the two anterior ones larger-sized and with thicker bundles of cilia than the posterior one (aso and pso, Figs. 7e, 8d).

Figures

Fig. 8 Schematic drawing of the nervous system in Rastrognathia macrostoma as inferred from serotonin-like (a–c) and tyrosinated tubulin-like (d and e) immunoreactivity and CLSM. a Entire body. b Head and pharyngeal regions, dorsal structures. c Head and pharyngeal regions, ventral structures. d Head and pharyngeal region, projection of both dorsal and ventral structures, dorsal view. Only one out of four pairs of compound cirri is shown. e Posterior region, dorsal view. Abbreviations: ap anterior perikaryon; aso anterior spiral organ; b brain; bg buccal ganglion; bn buccal nerve; cc compound cirri; dac dorso- anterior commissure; dc dorso- lateral nerve cord; dp dorsal perikaryon; lc lateral nerve cord; lp lateral perikaryon; mdc middorsal cell; mo mouth opening; mp median perikarya; np neuropil; p penis; pb pharyngeal bulb; pc posterior commissure; pcc posterior cell cluster; pso posterior spiral organ; te testis; vac ventro-anterior com- missure; vco ventral ciliary organ; vlc ventro-lateral nerve cord; vpc ventro-posterior commissure