OXYGEN-CONSUMPTION BY AMMOCOETES OF THE LAMPREY GEOTRIA-AUSTRALIS IN AIR

When covered by moistened lint-free gauze, the larvae (ammocoetes) of the lamprey Geotria australis survived, without apparent discomfort, f or 4 days in water-saturated air at 10, 15 and 20 degrees C. In air, t he mean standard rates of O-2 consumption of medium to large ammocoete s of G. australis ((x) over bar = 0.52 g) at 10, 15 and 20 degrees C w ere 14.5, 35.7 and 52.1 mu l . g(-1). h(-1), respectively. At 15 degre es C, the slope of the relationship between log O-2 consumption (mu l O-2 . h(-1)) and log body weight for ammocoetes over a wide range in b ody weight was 0.987. The Q(10)S for rate of O-2 consumption between 1 0 and 15 degrees C, 15 and 20 degrees C and 10 and 20 degrees C were 4 .9, 2.9 and 3.6, respectively. Our results and observations of the amm ocoetes suggest that, when out of water, larval G. australis derives m ost of its O-2 requirements from cutaneous respiration, particularly a t lower temperatures. This would be facilitated by the small size and elongate shape (and thus a relatively high surface-to-volume ratio), l ow metabolic rate, thin dermis, extensive subdermal capillary network and high haemoglobin concentration of larval G. australis.