Chemosensory anterior dorsal fin in rocklings (Gaidropsarus and Ciliata, Teleostei, Gadidae): somatotopic representation of the ramus recurrens facialis as revealed by transganglionic transport of HRP.
The anterior dorsal fin in rocklings consists of a fringe of 50-80 delicate, vibratile rays, which are densely beset with epidermal chemosensory cells. The innervation of these cells is from the dorsal branch of the recurrent facial nerve, which also innervates all other fins and the skin of the trunk. This nerve carries at least three classes of fibres: small (0.5-1.5 micron in diameter), medium (1.5-4 micron), and large (greater than 4 micron). Approximately 12,000 small and weakly myelinated nerve fibres from the recurrent facial nerve innervate the anterior dorsal fin organ. Application of HRP at different locations of the recurrent facial nerve labelled three different sizes of sensory perikarya within the geniculate ganglion--small (6-15 micron in diameter), medium (18-24 micron), and large (greater than 25 micron)--which corresponds to the different size classes of fibres present within the nerve. Retrograde transganglionic transport of HRP revealed somatotopy within the brainstem facial lobe: the delicate nerve fibres innervating the chemosensory anterior dorsal fin terminate exclusively in a distinct, dorsal portion of the facial lobe. Fibres innervating the posterior dorsal fin, the anal and caudal fins, as well as the skin of the trunk terminate within caudal and dorsal areas of the ventral facial lobe; pectoral and pelvic fins are represented in the ventral and caudal portions of the ventral facial lobe. Innervation by a distinct type of fibre and exclusive representation within a distinct, dorsal part of the facial lobe may indicate a peculiar biological role in the anterior dorsal fin chemosensory organ in the rocklings.
Kotrschal
K
K
Zoologisches Institut der Universität Salzburg, Austria.
Whitear
M
M
D000818:Animals; D001369:Axons / Q000648:ultrastructure; D001692:Biological Transport; D001931:Brain Mapping; D001933:Brain Stem / Q000502:physiology; D002628:Chemoreceptor Cells / Q000502:physiology*; D005154:Facial Nerve / Q000502:physiology* / Q000648:ultrastructure; D005399:Fishes / Q000502:physiology*; D005724:Ganglia / Q000166:cytology / Q000378:metabolism*; D006735:Horseradish Peroxidase / Q000378:metabolism*; D009474:Neurons / Q000502:physiology; D010544:Peroxidases / Q000378:metabolism*
D006735:Horseradish Peroxidase; D010544:Peroxidases