Marine Reptiles

Reptiles are cold blooded, air breathing animals with scales. They reproduce via internal fertilization, but lay their eggs on land. Some reptiles bear live young. Few reptiles live in salt water. These reptiles are sea snakes, marine lizards, crocodiles, and sea turtles.

Marine reptiles live mainly in tropical and subtropical oceans.

Reptiles have to live in warm climates because they are ectothermic, and they cannot tolerate wide temperature ranges. Reptiles depend on the external temperature (of the air and water) to regulate the temperature of their “cold-blooded” bodies. Like birds, marine reptiles have several adaptations which allow them to live and feed in and around the sea. Reptiles have a dry, scaly skin that protects against water loss. Marine reptiles also have salt glands, to help the body deal with the excess salt from the marine environment.

There are about 50 different species of sea snakes which range from one to two meters in length. Some sea snakes hunt fish, others eat fish eggs, but all are venomous. They have a paddlelike tail to aid in swimming and salt glands in the mouth enable snake to excrete excess salts and maintain water balance. Sea snakes also have a special flap of tissue to cover the nostrils during dives. Their lungs can inflate to 3.4 body length which enhances the capacity to hold air underwater. Sea snakes live in tropical waters; they do not live in the Atlantic.


The only marine lizard is the marine iguana. The marine iguana lives in the Galàpagos Islands. It swims and feeds on marine algae that grow on rocks in the subtidal zone and basks on rocks on land. Marine iguanas can swim by moving its flattened tail and its movements underwater are very graceful.

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Crocodiles are the largest of all reptiles. Crocodiles have a narrow snout and teeth that lie on the outside of the mouth when closed. They are opportunistic predators and feed on anything it can get its jaws on, but primarily crustaceans, fish and amphibians. Saltwater crocodiles spend the wet season in the freshwater swamps and move to the estuary during the dry season.

Sea turtles are over 200 million years old. In contrast to land turtles, the legs of sea turtles have been modified as swimming flippers. The ribs and the backbone of sea turtles are fused to the carapace and contrary to popular belief sea turtles can not bring their head into their shells. The top of the carapace is covered will scales called scutes. They have adapted to living in the ocean by extracting oxygen from water via their pharynx or anus and they can excrete excess salt through glands in eye sockets. Sea turtles have a great sense of time and location. However, despite these senses, all sea turtles are endangered. The three most endangered are the leatherback, hawksbill, and Kemp’s ridley. The sea turtles typically found on the east coast are the leatherback, green turtle, hawksbill, Kemp’s ridley, and loggerhead.

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