Long-term effects of hypothalamic lesions on the pituitary and its target organs in the killifishFundulus heteroclitus: II. Darkening

✍ Scribed by Pickford, Grace E. ;Knight, W. Rea ;Knight, Janet N. ;Baker, Bridget I.

• Publisher: John Wiley and Sons
• Year: 1984
• Tongue: English
• Weight: 965 KB
• Volume: 230
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1402300109

✦ Synopsis

Presumed lesions in the area of the nucleus preopticus (NPO) of male Fundulus heteroclitus resulted in chronic darkening in 12 fish. Sections revealed that all dark fish were severely injured in the nucleus opticus hypothalami (NOH) (Reperant et al., '82); in 11 cases there was injury to the optic tracts but in one the tracts were uninjured. Seven dark fish were tested on a white background: four were unable to assume pallor but three gradually paled. A caudal band remained dark in the four fish that did not fade but paled in the three that became slowly paler. It is concluded that the pathway to the thalamic paling center was destroyed but that low levels in melanophoreconcentrating hormone (MCH) persisted in the three fish whose denervated caudal bands faded. Darkening was not due to proliferation of new nielanocytes or to the synthesis of new melanin, but solely to a chronic state of melanophore dispersion. Pituitary melanocytes appeared mainly normal, and secretion of the melanophore-dispersing hormone was probably not excessive.

Bridgrt I. Baker's present address is Dcnprrrtirient of Biology, Uiiivc~sity of Bath, Bath HA3 7AT. England.