Almost all sea snakes are venomous, though with important distinctions regarding certain species. These reptiles have adapted remarkably to life in marine environments. This article explores what defines a sea snake, the characteristics of their potent venom, how to distinguish different types of marine snakes, and practical advice for safe encounters.
What Defines a Sea Snake?
True sea snakes belong to the subfamily Hydrophiinae, a group within the Elapidae family that includes terrestrial snakes like cobras. They evolved from land-dwelling ancestors and have specialized features for an aquatic existence. These reptiles are primarily found in the warm, tropical waters of the Indian and Pacific Oceans.
Physical adaptations for marine life include a paddle-like tail that aids propulsion. Many species also have laterally compressed bodies, particularly those living in open ocean environments.
Their nostrils are positioned on top of the snout with valves that close underwater, and they possess specialized salt-excreting glands, often located under the tongue, to manage excess salt.
Unlike most land snakes, many true sea snakes have greatly reduced or absent ventral scales, which makes them essentially helpless on land. They have elongated lungs that extend almost the entire length of their bodies, assisting with buoyancy and allowing for extended dives. Some species can even absorb a portion of their oxygen needs through their skin, further enhancing their ability to remain submerged.
The Potency of Sea Snake Venom
Most sea snakes possess highly potent venom, which they use to immobilize their prey. This venom typically contains neurotoxins, affecting the nervous system, and myotoxins, impacting muscle tissue. Symptoms of a sea snake bite can be delayed for several hours and may include muscle pain, weakness, and difficulty swallowing. More severe effects can progress to paralysis, including respiratory muscles, and even kidney damage due to muscle breakdown products.
Despite the high potency of their venom, bites to humans are rare. When bites do happen, sea snakes often do not inject venom, resulting in “dry bites.” Their fangs are generally small, and some species may have difficulty penetrating thick materials like wetsuits. Sea snakes are typically docile and usually only bite if threatened, accidentally stepped on, or entangled in fishing nets.
Distinguishing True Sea Snakes from Other Marine Snakes
While nearly all true sea snakes (Hydrophiinae) are venomous, the term “sea snake” can sometimes encompass other marine reptiles, leading to confusion. A distinction lies with sea kraits (subfamily Laticaudinae). Sea kraits are also venomous, but they are semi-aquatic, retaining physical characteristics that allow them to move on land.
They possess enlarged ventral scales, similar to terrestrial snakes, which provide grip for crawling and climbing on land. Unlike true sea snakes, sea kraits regularly return to land to lay eggs and shed skin. Their tails are paddle-like, but their bodies are typically more cylindrical compared to the laterally compressed true sea snakes.
One noteworthy exception to venomous sea snakes is the genus Emydocephalus, also known as turtle-headed sea snakes. These true sea snakes lack venom and have reduced dentition, as their diet consists almost exclusively of fish eggs. Other marine reptiles, such as sea turtles or marine iguanas, are non-venomous and not related to snakes. Eels, though serpentine in appearance, are fish and do not possess venom, though some can deliver a bite or an electric shock.
Safety and Encounters with Sea Snakes
Sea snakes are generally not aggressive towards humans, and bites are uncommon. Most incidents occur when individuals unintentionally provoke the snake, such as by stepping on one or attempting to handle it. Fishermen are susceptible to bites when disentangling snakes from nets.
Observing sea snakes from a distance is the safest approach. Avoid sudden movements that might startle the snake and never attempt to provoke or handle these animals. If in shallow waters, paying attention to where you step can prevent accidental encounters.
Should a bite occur, immediate medical attention is necessary. Remove the person from the water and keep the affected limb still. Applying a pressure-immobilization bandage can help slow the spread of venom, but it should not cut off circulation. Avoid traditional first aid measures like attempting to suck out venom, cutting the wound, or applying a tourniquet, as these are ineffective and can cause further harm.