We continue to focus on the ocean during Plastic Free July and this week we cover the family of Sea Snakes. We could not just pick one, so we go ahead and cover the generalities of the 69 or so species of Sea Snakes. While highly venomous, Sea Snakes are actually quite docile and are important contributors of many of our oceanic habitats.
Sea Snake History
Snakes date back at least 170 million years. The first fossil of a snake was discovered in southern England with Eophis underwoodi. Since, snakes have migrated to almost every continent (excluding Antarctica). Snakes did not really thrive until the end of the dinosaurs after the 5th Mass Extinction about 65 million years ago.
The first venomous snake was found to be out of Africa, with being an elapid about 25 million years ago. Sea Snakes are members of the Elapidae family, along with cobras. Sea snakes specifically, eventually emerged in Southern Asia about 8 million years ago. Today’s species of Sea Snakes are thought to have been around for the past 1 million years.
Sea Snakes belong to the subfamily Hydrophiinae. Within this subfamily there are 17 genera and roughly 69 species. Sea Snakes are divided into:
- True Sea Snakes, which remain at sea almost all of their lives and give birth to live young
- Sea Kraits, which can come onto land and lay eggs
Sea Snake Physiology
These snakes have adapted to live and survive in an aquatic environment with many adaptations. One interesting physiological change is the snakes oar like tails. This allows them to swim like eels, yet maintain other characteristics of land snakes. Other facts include:
- Sea Snakes and Kraits need to breath like land snakes. However, true Sea Snakes can submerge for much longer periods, up to 3 hours. They do this because they have an ability to absorb oxygen through their skin, and expel carbon dioxide.
- Generally live in waters less than 100 feet (30 meters)
- Sea Snakes flick their tongues in water and can “smell”
- Sea Snakes excrete excess salt with their tongues due to excretion of subliminal glands under their tongues
- Sea Snakes are highly venomous, with a mixture of neurotoxins and myotoxins
- Sea Snakes are quite docile and it is very rare for them to strike humans
- Sea Snake diets include fish, young octopus, small eels, crustaceans, and even fish eggs
Much is still not known about many of species of Sea Snakes. However, some are considered critically endangered. The Short-Nosed and Leaf-Scaled Sea Snakes are critically endangered. Others are listed as vulnerable or under concern.