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, for 4 days in water-saturated air at 10, 15 and 20 degrees C. In air, the mean standard rates of O2 consumption of medium to large ammocoetes of G. australis (mean = 0.52 g) at 10, 15 and 20 degrees C were 14.5, 35.7 and 52.1 microliters.g-1.h-1, respectively. At 15 degrees C, the slope of the relationship between log O2 consumption (microliter O2.h-1) and log body weight for ammocoetes over a wide range in body weight was 0.987. The Q10s for rate of O2 consumption between 10 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 ammocoetes suggest that, when out of water, larval G. australis derives most of its O2 requirements from cutaneous respiration, particularly at lower temperatures. This would be facilitated by the small size and elongate shape (and thus a relatively high surface-to-volume ratio), low metabolic rate, thin dermis, extensive subdermal capillary network and high haemoglobin concentration of larval G. australis.