Nonphotic stimuli alter a day-night rhythm of allograft rejection in gulf killifish

Department of Zoology and Physiology, Louisiana State University, Baton Rouge 70803, USA.
Developmental & Comparative Immunology (Impact Factor: 2.82). 11/1994; 18(6):495-509. DOI: 10.1016/S0145-305X(06)80004-2
Source: PubMed

ABSTRACT The influence of environmental stimuli on a daily rhythm of immune activity during scale allograft rejection was investigated in gulf killifish, Fundulus grandis. Although melanophore destruction in the grafts is largely restricted to the scotophases in killifish held on 12 h daily photoperiods (LD 12:12), timed daily netting (tank-transfer "stress"), thermoperiods (from 20 degrees to 30 degrees C for 4 or 12 h), and feeding altered the expression of this rhythm. Melanophore breakdown peaked 0-12 h after netting or thermoperiod onset and 12-24 h after feeding, whether the fish were exposed to these nonphotic daily stimuli at the onset or offset of 12-h photoperiods. In fish held under continuous light and pretreated with these daily stimuli, 24-h immune activity rhythms persisted in the altered phases for several days after the daily treatments were stopped. These findings suggest that a daily rhythm of immune activity may have adaptive significance in fish.

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    ABSTRACT: The length of time required to reject scale allografts was examined in groups of male gulf killifish (Fundulus grandis) treated daily with either 4-h thermoperiods (daily intervals of 30°C during a 20°C continuum), single meal feedings, or net-chasing disturbances at one of six different times after the onset of daily photoperiods (LD 12:12 or LD 14:10). Scale allograft survival varied by 30–60% in each timed stimulus experiment as a function of the time of day when the stimulus was provided. The phase relationship between two circadian neuroendocrine oscillations, previously proposed to regulate physiologic and behavioral conditions in gulf killifish, may have important influences on the immune system as well. The phase of one oscillation is thought to be set by the daily photoperiod, and the other is preferentially set by the nonphotic daily stimulus. © 1995 Wiley-Liss, Inc.
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