A reappraisal of the aquatic specializations of the Galapagos marine iguana (Amblyrhynchus cristatus).
- 891-897.
Contrary to earlier descriptions, the Galapagos marine iguana is not a particularly fast swimmer, the mean velocity for burst swimming by large adults being only 0.85 m/s. Moreover, this lizard depends on physiological patterns characteristic of terrestrial iguanids in its amphibious existence. Aerobic metabolic scope is relatively restricted and highly dependent upon body temperature. This function reaches a maximum at 35 C, a value characteristic of basking marine iguanas, but substantially higher than the water temperatures at which the most strenuous activities of this species occur. Its abilities to forage in cool waters appear to depend upon substantial anaerobic capacities, which resemble those of terrestrial iguanids. As in these other lizards, anaerobic metabolic scope appears relatively independent of temperature in the marine iguana. Physiological results and a review of the probable events leading to the evolution of the Galapagos marine iguana support a view of this animal as a representative of a terrestrial line that was preadapted for exploiting a unique combination of circumstances.