Dracoderes abei, Higgins and Shirayama, 1990

Herranz, Maria, Sørensen, Martin V., Park, Taeseo, Leander, Brian S. & Worsaae, Katrine, 2020, Insights into mud dragon morphology (Kinorhyncha, Allomalorhagida): myoanatomy and neuroanatomy of Dracoderes abei and Pycnophyes ilyocryptus, Organisms Diversity & Evolution (New York, N. Y.) 20 (3), pp. 467-493 : 479

Neuroanatomy of D. abei

Tubulinergic nervous system

Acetylated α- tubulin-like immunoreactivity (α- tub-LIR) in D. abei shows a circumpharyngeal brain with several longitudinal bundles originating radially from the anterior brain region, and extending along the introvert and trunk ( Figs. 6, 7, and 8). The neuropil (np) is composed of a set of condensed neurites forming a ring that narrows on the ventral side ( Figs. 6a, b and 8a, b). Connected to the anterior part of the neuropil, ten radially arranged neurite bundles (lnb) originate in the anterior brain region and extend anteriorly along the introvert, bend 180° toward the body wall and extend posteriorly along the trunk ( Fig. 8a, b, d). These neurite bundles have different thicknesses, with the ventromedial bundles being much more prominent than the rest (Figs. 7b, c, and 8a, b). At the level of segments 1 to 2, the longitudinal neurite bundles merge two by two forming five longitudinal nerves: one ventromedial, two ventrolateral, and two subdorsal ( Fig. 8a, b, d–f). The paired ventromedial prominent longitudinal bundles converge into a midventral nerve cord (vnc) that extends posteriorly throughout the trunk ( Figs. 6a, b, 7b, c, and 8b). Within segment 8, the ventral nerve cord splits into two neurite bundles (vncn). From each branch, two peripheral neurites originate and innervate segments 9, 10, and 11, and extend laterally to connect with the subdorsal nerves ( Figs. 6d, e and 8a, b). From segments 1 to 2, the ventrolateral (vln) and subdorsal nerves (sdn) extend toward trunk segments 8 and 9, respectively ( Fig. 8b). The subdorsal nerves, ventrolateral nerves, and ventral nerve cord are interconnected through circular transverse neurites (tn) that originate from left and right sides of the ventral nerve cord, medially in segments 1–9 ( Fig. 6a, b and 8a, b). The transverse neurites are unpaired in segment 1 and paired in segments 2–9. Additionally, thin diagonal neurites are present ventrally in some trunk segments but without a consistent pattern. Of the five trunk nerves, the ventral nerve cord is the only one that has associated nuclei. These nuclei are arranged along the ventral cord and seem to condense into discrete segmental ganglia in segments 1–8 ( Fig. 6g, d). In specimens with a contracted trunk these ganglia are so close to each other that it is difficult to distinguish them individually, giving the appearance of a medullary cord. In segments 8–9, the aggregation of somata in the ventral nerve cord is continuous, extending also into the intersegmental area ( Fig. 6d). The architecture of the tubulinergic nervous system of D. abei exhibits a segmental organization from segments 1 to 8.