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Table 1 Comparison of nervous system architecture within Kinorhyncha. Abbreviations: np, neuropil; ios, inner oral styles; oos, outer oral styles; so, somata; ss, sensory spots; vnc, ventral nerve cord. Question marks represent absence of data

From: Neuroanatomy of mud dragons: a comprehensive view of the nervous system in Echinoderes (Kinorhyncha) by confocal laser scanning microscopy

Species Data source Brain Number of longitudinal nerves Transverse neurites (commissures) Vnc Innervation of introvert scalids Innervation mouth cone Innervation of neck Innervation of trunk cuticular structures References
A. paulae CLSM Circumpharyngeal with 3 regions
(So-Np-So)
? ? Paired origin of vnc ? Serotonin positive nerve ring ? ? [29]
E. capitatus TEM Circumpharyngeal with 3 regions
(So-Np-So)
Ten lobbed anterior somata
10 fusing into 5
(2 subdorsal, 2 ventrolateral and 1 vnc)
2 per trunk segment Paired origin of vnc
Single ganglion per segment
Neurites from the 10 longitudinal nerves 9 nerves innervating the oos from the “hindbrain” fusing into 5 nerves innervating ios
Proximal and terminal nerve ring
10 longitudinal nerves Spines, tubes (named “setae”) and ss innervated from the 5 longitudinal nerves of the trunk [24, 25, 38]
E. aquilonius TEM Circumpharyngeal with 3 regions
(So-Np-So)
8 “Circular nerve fibers” in each segment Paired origin of vnc
Double ganglia per segment
Neurites from the anterior perikarya of the brain 10 nerves innervating the oos from the "forebrain"
Proximal and terminal nerve ring
Neurites from the longitudinal nerves Spines, ss, tubes innervated from the middorsal, laterodorsal and ventrolateral cords [26]
E. horni
E. spinifurca
E. ohtsukai
CLSM Circumpharyngeal with 3 regions
(So-Np-So)
Ten lobbed anterior somata
10 fusing into 5 (2 subdorsal, 2 ventrolateral and 1 vnc) 2 per trunk segment (except for segments 1, 10-11) Paired origin of vnc
Single ganglion per segment
Radially arranged neurites arising from the neuropil 9 nerves innervating the oos arising from the neuropil
Anterior nerve ring
10 longitudinal nerves + 2 circular
neurites
Spines, ss, tubes, and nephridia innervated from transverse neurites
Terminal spines innervated from longitudinal neurites from the vnc
Present study, [29]
P. greenlandicus TEM Circumpharyngeal with 3 regions
(So-Np-So)
8 “Circular nerve fibers” in each segment Paired origin of vnc
Double ganglia per segment
Neurites from the anterior perikarya of the brain 10 nerves innervating the oos from the "forebrain"
Proximal and terminal nerve ring
Neurites from the longitudinal nerves Spines, ss, tubes innervated from the longitudinal cords [26, 48]
P. dentatus TEM Circumpharyngeal with 3 regions
(So-Np-So)
7 ? Paired origin of vnc (only illustrated) ? 9 nerves innervating the oos from the posterior brain region ? ? [34, 49]
S. kielensis TEM, CLSM Circumpharyngeal with 3 regions
(So-Np-So)
8 (TEM) At least one “nerve” per segment (CLSM) Paired origin of vnc (only illustrated) (TEM)
1 ganglion per segment (TEM)/ 1 ganglion in vnc segment 6 (CLSM)
? 9 nerves innervating the oos (TEM) ? ? [28, 48]
Z. brightae CLSM Circumpharyngeal with 3 regions
(So-Np-So)
? ? Paired origin of vnc ? Serotonin positive nerve ring ? ? [29]
Z. floridensis TEM Circumpharyngeal with 3 regions
(So-Np-So)
12 ? ? ? 9 nerves innervating the oos ? ? [49]