Neuroepithelial cells and the hypoxia emersion response in the amphibious fish Kryptolebias marmoratus

Teleost fish have oxygen-sensitive neuroepithelial cells (NECs) in the gills that appear to mediate physiological responses to hypoxia, but little is known about oxygen sensing in amphibious fish. The mangrove rivulus, Kryptolebias marmoratus, is an amphibious fish that respires via the gills and/or...

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Bibliographic Details
Published in:	Journal of experimental biology Vol. 214; no. Pt 15; pp. 2560 - 2568
Main Authors:	Regan, Kelly S, Jonz, Michael G, Wright, Patricia A
Format:	Journal Article
Language:	English
Published:	England 01-08-2011
Subjects:	Animals Chemoreceptor Cells - cytology Chemoreceptor Cells - drug effects Cyprinodontiformes - physiology Gills - cytology Gills - physiology Hexamethonium - pharmacology Hypoxia - physiopathology Immunohistochemistry Ketanserin - pharmacology Microscopy, Fluorescence Neuroepithelial Cells - cytology Neuroepithelial Cells - drug effects Nicotinic Antagonists - pharmacology Oxygen - metabolism Respiration Rivulus Serotonin - metabolism Serotonin Antagonists - pharmacology Skin - cytology Skin Absorption Skin Physiological Phenomena Teleostei Vesicular Acetylcholine Transport Proteins - metabolism
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Summary:	Teleost fish have oxygen-sensitive neuroepithelial cells (NECs) in the gills that appear to mediate physiological responses to hypoxia, but little is known about oxygen sensing in amphibious fish. The mangrove rivulus, Kryptolebias marmoratus, is an amphibious fish that respires via the gills and/or the skin. First, we hypothesized that both the skin and gills are sites of oxygen sensing in K. marmoratus. Serotonin-positive NECs were abundant in both gills and skin, as determined by immunohistochemical labelling and fluorescence microscopy. NECs retained synaptic vesicles and were found near nerve fibres labelled with the neuronal marker zn-12. Skin NECs were 42% larger than those of the gill, as estimated by measurement of projection area, and 45% greater in number. Moreover, for both skin and gill NECs, NEC area increased significantly (30-60%) following 7 days of exposure to hypoxia (1.5 mg l(-1) dissolved oxygen). Another population of cells containing vesicular acetylcholine transporter (VAChT) proteins were also observed in the skin and gills. The second hypothesis we tested was that K. marmoratus emerse in order to breathe air cutaneously when challenged with severe aquatic hypoxia, and this response will be modulated by neurochemicals associated chemoreceptor activity. Acute exposure to hypoxia induced fish to emerse at 0.2 mg l(-1). When K. marmoratus were pre-exposed to serotonin or acetylcholine, they emersed at a significantly higher concentration of oxygen than untreated fish. Pre-exposure to receptor antagonists (ketanserin and hexamethonium) predictably resulted in fish emersing at a lower concentration of oxygen. Taken together, these results suggest that oxygen sensing occurs at the branchial and/or cutaneous surfaces in K. marmoratus and that serotonin and acetylcholine mediate, in part, the emersion response.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0022-0949 1477-9145
DOI:	10.1242/jeb.056333