Properties of the melatonim-generating system of the sailfin molly, Poecilia velifera

The properties of the melatonin-generating system of a tropical teleost, th e sailfin molly (Poecilia velifera), were investigated in vitro in a series of experiments using static or perifusion culture techniques. The properti es examined included photic entrainment, circadian rhythmicity under contin uous light (LL) and continuous darkness (DD), functionality of the melatoni n-generating system at birth, and presence of multiple circadian oscillator s in the molly pineal. Pineal glands or skull caps with the pineal gland fi rmly attached were dissected from adult and new-born fishes, respectively, and placed into static or perifusion culture at constant temperature (27 de grees C) depending upon the experiment. Melatonin release in samples was qu antified by RIA. Rhythmic melatonin release was observed from isolated adul t pineals under 12L:12D and 14L:10D, with low amounts of melatonin released during the light and high amounts during the dark. Melatonin release was i nhibited by LL. However, under DD, melatonin release was robust and rhythmi c with a circadian period (Tau) that ranged between 21.3 and 27.0 h (n = 21 ). Pineals from newborn (1-day old) mollies released melatonin rhythmically under a light:dark cycle and DD in both static and perifusion culture. Mel atonin release from half and quarter pineals of adult mollies under DD was robust and rhythmic with circadian periods that ranged between 22.5 and 29. 0 h (n = 19). Taken together, these data show that the molly pineal is phot osensitive, fully functional from birth, and contains multiple circadian os cillators (at least four) regulating melatonin production. (C) 1999 Academi c Press.