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Table 4 Compilation of features of the nervous system in representatives of different annelid groups and Lobatocerebrum riegeri n. sp

From: Detailed reconstruction of the nervous and muscular system of Lobatocerebridae with an evaluation of its annelid affinity

   ANNELIDA
   PREVIOUS “PROBLEMATICA”, now ANNELIDA  
   LOBATOCEREBRIDAE DIURODRILIDAE ? SIPUNCULA DINOPHILIDAE PROTODRILIDAE PSAMMODRILIDAE NEREIDIDAE CAPITELLIDAE SERPULIDAE
   Lobatocerebrum riegeri n. sp. Lobatocerebrum psammicola Diurodrilus sp. Jennaria pulchra Phascolion strombus Siphonosoma australe Dinophilus gyrociliatus Protodrilus sp. Psammodrilus fauveli Platynereis sp. Capitella sp. Pomatoceros lamarckii Spirorbis cf. spirorbis
  Location of the ventral nerve cords Intraepithelial Intraepithelial Intraepithelial Intraepithelial Intraepithelial Intraepithelial Intraepithelial Intraepithelial Intraepithelial Intraepithelial Intraepithelial Intraepithelial Intraepithelial
BRAIN Lobular structure + + ? + ? ? - - + + + - +
Central neuropile + + + + + + + + + + + + +
Number of brain commissures 4 ? 4 ? 2 1 2 4 4 4 4 4 4
Dorsal root (dorsal/ventral commissure) + (+/+) ? + (+/+) ? ? - (Not differentiated in this species) ? + (+/+) + (+/+) + (+/+) + (+/+) + (+/+) + (+/+)
Ventral root (dorsal/ventral commissure) + (+/+, individual fibres spread out) ? + (+/+) ? ? - (Not differentiated in this species) ? + (+/+) + (+/+) + (+/+) + (+/+) + (+/+) + (+/+)
NERVE CORDS OF THE CENTRAL NERVOUS SYSTEM Number of posterior longitudinal nerve cords 1 pair + 1 median cord 1 pair (+1 median cord?) 2 pairs 1 pair 1 pair 1 pair (fused during development) 3 pairs + median cord 1 pair 1 pair 1 pair 1 pair 1 pair 1 pair
Median posterior nerve cord + ? - - - - + - - - + + -
Number of rostral longitudinal nerve cords 2 ventrolateral + < 7 additional, smaller ones 2 (?) >2 ? 0 0 0 0 (but innervation of tentacles) 0 0 0 0 (but innervation of tentacles) 0 (but innervation of tentacles)
GANGLIA AND COMMISSURES ALONG THE VENTRAL NERVE CORD Total number of ganglia 2 pairs 2 pairs 1 (fused pair) ? >2 >2 (during development) >2 >2 >2 >2 >2 >2 1 (in larvae)
Nonganglionated posterior commissures >2 2 >2 1 ? >2 (during development) >2 >2 >2 >2 >2 >2 1 (in larvae)
Presence of a subpharyngeal ganglion + + + ? + + (during development) + + + + + + +
STOMATOGASTRIC NERVOUS SYSTEM Stomatogastric nervous system + (ring around the pharynx) + (ring around the pharynx) + (ring around the esophagus) + (nerve cells in the pharyngeal epithelium) + (ring around the esophagus + (ring around the esophagus, during development) + (ring around the pharynx) + (ring around the esophaus) + (ring around the esophagus, also tracing the esophagus) + (ring around the esophagus) + (ring around the esophagus) + (fibre along the gut, ring around the esophagus) -
Origin of the stomatogastric nervous system Postpharyngeal ganglion Postpharyngeal ganglion prebuccal ganglion ? brain (?) brain (?) Brain (dorso-posterior neuropile) Brain Buccal ganglion Brain Brain Brain -
PERIPHERAL NERVOUS SYSTEM   Grid of distinct longitudinal and circular nerves ? 1 pair of longitudinal nerves, several branches for innervating organs Some nerves around the pharynx and gut, otherwise not present or not described Nerve plexus ? Regular grid of longitudinal and circular nerves, nerve plexus dorsal to the ventral nervous system ? ? Grid of distinct longitudinal and circular nerves Grid of distinct longitudinal and circular nerves Circular nerves in some segments Grid of distinct longitudinal and circular nerves
References   This study [811] [61] [9, 83] [57, 73] [58] [14, 84, 85] [55, 86] [87, 88] [70, 89, 90] [91] [92] [92]
  1. Details of the brain, the ventral nervous system, the stomatogastric nervous system and the peripheral nervous system are given in an attempt to reveal common features or possible apomorphies in Lobatocerebridae. Presence of a character is labeled with +, absence with -, numbers and additional informations are given wherever possible. ? indicates the lack of information in the references mentioned, while reinvestigations from this study (in the case of L. riegeri n. sp.) and assumptions based on additional references are included by putting the assessment in brackets (+) or (−). Insufficient information in one species was supplemented with closely related species, based on the literature acknowledged in the reference-row