Record Details

Bartholomew, George A;Bennett, Albert F;Dawson, William R
Swimming, diving and lactate production of the marine iguana, Amblyrhynchus cristatus
Journal Article
Amblyrhynchus cristatus
The swimming and diving performance of hatchling, juvenile and adult marine iguanas, and the effects of these activities on blood lactate in juveniles were studied under field conditions at Academy Bay, on Isla Santa Cruz, in the Galapagos Islands. By appropriate selection of microclimate, all size classes of marine iguanas maintain body temperatures between 35 and 37 C during the hours of daylight. Despite strong sexual dimorphism no pronounced allometry in body proportions occurs during growth. Newly hatched young are effective swimmers but do not voluntarily enter the water. They feed on algae exposed in the intertidal. Juvenile animals confine their aquatic activity to shallow water and feed mostly in the intertidal zone. Adults also feed in the intertidal but do much of their feeding underwater in subtidal areas. During both burst and cruise swimming, velocity and distance traveled per undulation increase directly with size, whereas body lengths/sec, body length/undulation and rate of undulation are inversely related to body size. The absolute velocity and the length-specific velocity of both the burst and cruise swimming of marine iguanas are very slow when compared with bony fish of similar size. The burst swimming of unrestrained marine iguanas results in a sharp increase in blood lactate, but cruise swimming is apparently supported aerobically. After 10 min of forced submergence under water mean blood lactate of juveniles increased about 38 mg%; after one hour of forced submergence it increased by 137 mg%. Marine iguanas appeared exhausted after one hour underwater, could not right themselves, and could not be induced to run. The role of anaerobiosis in both the aquatic and terrestrial activity of Amblyrhynchus is discussed and the zoogeographic implications of its swimming performance are examined.