OXYGEN-CONSUMPTION BY ADULTS OF THE SOUTHERN-HEMISPHERE LAMPREY GEOTRIA-AUSTRALIS IN AIR

Adults of the lamprey Geotria australis are capable of surviving and t aking up considerable volumes of oxygen when in humidified air. This a ccounts for their ability to leave water, move through moist vegetatio n and up and over dam walls, and thereby overcome barriers to their up stream migration. Immature adults of G. australis, which had been on t heir spawning run for 3-4 months, survived for at least 30 hr and with out apparent discomfort in humidified air at 15 degrees C during a lig ht/dark/light regime paralleling field conditions. The mean hourly rat e of oxygen consumption of these lampreys stabilised at c. 48 mu l.gm( -1).hr(-1) during the light phase, but then rose during the dark phase and remained at c. 66 mu l.gm(-1).hr(-1), before declining during the second light phase to a level similar to that in the initial light ph ase. The mean standard rate of oxygen consumption in air and in light, based on the minimal values recorded for individual animals during th e period when their oxygen consumption was low and stable, was 33.6 mu l.gm(-1).h(-1), which is virtually identical to the standard rate of oxygen consumption of immature adult G. australis, measured previously in water and light at the same temperature. However, the above mean r ate for standard oxygen consumption in air is significantly less (P < 0.001) than the mean rate of 50.4 mu l.gm(-1).hr(-1), determined in th e same manner in air during those periods at night when oxygen consump tion was high and stable. At the end of the spawning run, when maturit y is attained, the mean standard rates of oxygen consumption of male a nd female G. australis in air and light at 15 degrees C were 32.8 mu l .gm(-1).hr(-1) and 22.6 mu l.gm(-1).hr(-1), respectively. (C) 1996 Wil ey-Liss, Inc.