Marine Iguanas - TS

The marine iguana (Amblyrhynchus cristatus) is an iguana found only on the Galápagos Islands that has the ability, to forage in the sea. It has spread to all the islands in the archipelago, and is sometimes called the Galápagos marine iguana. It mainly lives on the rocky Galápagos shore but can also be spotted in marshes and mangrove beaches.

Description
Marine iguanas are medium-sized lizards with the average length of an adult male being approximately 1.3m and average length of an adult female being approximately 0.6m. The weight of these iguanas range between 0.5-1.5kg and are unique as they forage on inter and subtidal algae only, making them marine reptiles. The iguana can dive over 9 m into the water and stay submerged for around an hour, however they normally do shallow dives for around 10 minutes.

Amblyrhynchus cristatus is not always black; the young have a lighter coloured dorsal stripe, and some adult specimens are grey, and adult males vary in colour with the season. The marine iguana lacks agility on land but is a good swimmer. Its laterally flattened tail and spiky dorsal fin aid in propulsion, while its long, sharp claws allow it to hold onto rocks in strong currents. They are distinguished from land iguanas by their short, blunt snouts and compressed tail. These adult iguanas forage exclusively in the cold sea, which leads them to behavioural adaptations for thermoregulation.

Thermoregulation
Marine iguanas generally aim to attain temperatures of around 36 degrees Celsius before going in the water to look for food. When in the ocean, their body temperatures often drop by around 10 degrees. Higher body temperatures also encourage proper swimming and digestive functioning in the iguanas.

Since marine iguanas can't manage their body temperatures by themselves (they are ectothermic), they turn to basking in the sun as a means of getting warm after a dive, and often bask immediately after returning to land. The reptiles position their bodies straight over lava rocks in attempts to get their skin to soak up optimal amounts of sun. Dark tones allow the lizards to rapidly absorb heat to minimize the period of lethargy after emerging from the water. After sunrise, they spend several hours basking away before they proceed with their day. Until it can warm up it is unable to move effectively, making it vulnerable to predation. However, this is counteracted by their highly aggressive nature consisting of biting and expansive bluffs when in this disadvantageous state.

Marine iguanas also possess vessels within their chests that manage their bodies' heat supplies. The vessels constantly open and shut in order to keep body temperature controlled and stable.