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
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 | |
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 | |
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 | ? | ? | |
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) | ? | ? | |
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] |