Neuroepithelial cells and associated innervation of the zebrafish gill: a confocal immunofluorescence study.
Peripheral chemoreceptors responsive to hypoxia have been well characterized in air-breathing vertebrates, but poorly in water-breathers. The present study examined the distribution of five populations of neuroepithelial cells (NECs), putative O(2) chemoreceptors, and innervation patterns in the zebrafish gill using whole-mounts and confocal immunofluorescence. Nerve bundles and fibers of the gill were labeled with zn-12 (a zebrafish-specific neuronal marker) and SV2 antisera and NECs were characterized by serotonin (5-HT) immunoreactivity (IR), SV2-IR and the purinoceptor P2X(3)-IR. A zn-12-IR nerve bundle extended the length of the gill filament and gave rise to a nerve plexus surrounding the efferent filament artery (eFA) and a rich network of fibers that innervated both serotonergic and nonserotonergic NECs of the filament and lamellar epithelium. Three populations of serotonergic, SV2-IR neurons intrinsic to the gill filaments are described, one of which provided innervation to NECs of the filament epithelium. Degeneration of nerve fibers in gill arches maintained in explant culture for 2 days revealed the extrinsic origin of nerve fibers of the plexus and lamellae and the innervation of filament NECs by both intrinsic and extrinsic fibers. Intrinsic innervation surrounding the eFA survived in explant cultures, suggesting a mechanism of local vascular control within the gill. In addition, NECs survived in explants after degeneration of extrinsic nerve fibers. Thus, NECs of the zebrafish gill are organized in a manner reminiscent of O(2) chemoreceptors of mammalian vertebrates, suggesting a role in respiratory regulation.
Department of Biology, Life Sciences Building, McMaster University, Hamilton, Ontario L8S 4K1, Canada.
Michael G
MG
Jonz
Colin A
CA
Nurse
D000818:Animals; D015415:Biomarkers / Q000032:analysis; D002628:Chemoreceptor Cells / Q000737:chemistry*; D004847:Epithelial Cells / Q000737:chemistry*; D004848:Epithelium / Q000033:anatomy & histology / Q000737:chemistry / Q000294:innervation; D005455:Fluorescent Antibody Technique; D005880:Gills / Q000166:cytology* / Q000294:innervation*; D008562:Membrane Glycoproteins / Q000032:analysis; D018613:Microscopy, Confocal; D009410:Nerve Degeneration; D009419:Nerve Tissue Proteins / Q000032:analysis; D009474:Neurons / Q000737:chemistry*; D009924:Organ Culture Techniques; D010100:Oxygen / Q000097:blood; D018048:Receptors, Purinergic P2 / Q000032:analysis; D058477:Receptors, Purinergic P2X3; D012701:Serotonin / Q000032:analysis; D014018:Tissue Distribution; D015027:Zebrafish / Q000502:physiology*
D015415:Biomarkers; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D018048:Receptors, Purinergic P2; D058477:Receptors, Purinergic P2X3; D012701:Serotonin; D010100:Oxygen