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Old 01-21-2002
Ralph Doolin Ralph Doolin is offline
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Sea Snakes

This article was originally published on SailNet in July, 2000.


Poisonous sea snakes are found predominantly in the tropical waters of the Western Pacific and Indian Oceans, especially in protected coastal waters. Yet another risk that sailors cruising in these areas need to be aware of.
I don't know about you, but I'm a little afraid of snakes. I don't want to be around them and I really have no desire to handle them. I don't even like to handle eels—after all, they look a lot like snakes. For many of us, snakes remain a source of nightmares, misconceptions, and, for a few weird friends, adoration. Believe it or not, there are cultures that believe the snake represents the reincarnation of an important person or serves as an object of worship and praise. In Judeo-Christian circles on the other hand, the snake has been on the hit list since that historic day in the Garden of Eden.

Neverthless, snakes serve a very important role on our ecosystem and the importance of these reptiles cannot be understated. I don't, but many people do, wish a death sentence on every snake they see. I leave them alone and hope that they will leave me alone so that we can peacefully coexist. No, I am not terrified of these creatures, but I do respect them and give them their space and a wide berth. I am told that people who are educated about snakes have no fear. That may be true, but I will never be comfortable handling them.

Sailors, mainly saltwater sailors, have a fair chance of encountering snakes. There is a large group (several dozen species) of very poisonous snakes that inhabit marine environments, but most of them remain relatively unstudied. And these sea snakes (true snakes) have completely adapted to life in the sea.

Poisonous sea snakes are found predominantly in the tropical and subtropical waters of the Western Pacific and Indian Oceans, most often in and near river mouths and protected coastal waters. The pelagic sea snake, pelamis platurus, has a remarkably wide geographic range, which reaches the western coasts of North and South America from the Baja peninsula to Ecuador, and the waters around Hawaii. Poisonous sea snakes are not found in the Atlantic Ocean, the Caribbean, or along the North American coast north of Baja. The only US State in which sea snakes are found is Hawaii.

 
When fishing the reefs, the sea snake's breath-holding ability is prodigious.
 
Many Caribbean islands are cut by deep bays and coves and some adjacent land areas are occupied by venomous snakes. Adventurous cruisers may elect to travel through alligator-infested mangrove swamps where the trees are the natural habitat of scarlet ibis and snakes such as the water moccasin. These land-based snakes swim quite well and you may see one of them crossing a cove or lagoon, or traversing other waterways close inshore. These are not sea snakes, however, and it would be prudent not to approach, threaten, or interrupt their journey since they may be poisonous.

All snakes are cold-blooded creatures. Consequently, their distributions are restricted to warm waters and true sea snakes are only found in the Indo-Pacific region. There is concern that if a sea-level canal were constructed across Panama, they could become introduced to the Caribbean.

The sea snake is a true air-breathing reptile. These critters can hold their breath for long periods while hunting, and even sleeping, on the reef. They must eventually come to the surface for a quick breath of air and these brief trips to the surface can scare the devil out of curious divers and fishermen since the snake will often swim directly at a hovering diver or boat on the way to the surface. These snakes mate and give birth to their young on the shore, but spend the rest of their lives hunting fish, crustaceans, and eels amongst the nooks and crannies of the reef. Snakes make their rounds along a reef, and their persistence (not to mention breath-holding ability) is impressive.

 
Just because most sea snakes exist in Indo-Pacific waters, that doesn't mean you won't see a poisonous land snake swim by elsewhere, particularly along the coast of Central America.
 
Sea snakes are one of the most poisonous creatures on the reef, with venom similar to that of the cobra. Fortunately, they are not aggressive and fatal encounters with divers have rarely been reported. In addition to their mellow nature, they have short fangs unlikely to penetrate even a tropical wet suit and seldom envenomate even when biting. These critters are laid back and unlikely to attack. There have been deaths reported, but these were usually fishermen encountering snakes in their nets. Sea snakes are noted for their poor eyesight, but studies show that they have excellent chemical sensation and they have the same forked tongue as their land-based cousins for sensing vibration.

There are over 31 species of sea snakes in northern Australian waters alone. All are possibly dangerous to humans, but relatively few of these have caused bites of significance. Even though, sea snakes are found predominantly in the northern waters of Australia, storms may carry an occasional specimen southward, with authenticated bites as far south as Sydney. They are not likely to be found in waters off the southern coast of Australia, where alleged sea snake bites are essentially always due to some other organism, usually an eel.

 
This banded sea snake is poisonous, but fortunately this species is known to be pretty laid back.
 
The venom delivery system of sea snakes is fairly rudimentary, consisting of two or four short, hollow, upper-jaw fangs associated with a pair of venom glands. The venom ducts open near the tips of the fangs. The fangs will easily dislodge from their sockets and may remain embedded in the skin of victims—ouch. A sea snake bite is usually felt, and comes with small, but distinct, teeth marks that are visible, and may be multiple, mostly from non-fang teeth. Pain at the bite site is not a major feature, nor is swelling. The important effects, seen in only some cases, are systemic and may include paralysis. If envenoming has occurred, then the effects may be expected within six hours in most cases, manifested as early paralysis (e.g. drooping of the upper eyelids, erratic movements of the eyes, and of the pupils, limb or respiratory weakness, muscle pain, and weakness).

"If you get bitten, anti-venom will probably not be readily available, even though evidence of paralysis indicates the patient should receive it."
If you get bitten, anti-venom will probably not be readily available, even though evidence of paralysis indicates the patient should receive it. CSL Sea Snake Anti-Venom is the first choice, starting with an initial dose of one to three ampoules, depending on the severity and rapidity of onset of envenoming. Up to 10 ampoules have been used in severe cases. Obviously a physician should do this. Applying anti-venom on board as first aid would not be advisable.

There is just not much to do for a bite while underway. The use of adrenaline as pre-treatment when using anti-venoms is still being studied. There is risk of an acute systemic allergic reaction that can be fatal, but varies from one anti-venom to another. People who have had previous exposure to equine derived products may be at greater risk. Should you have any anti-venom products on board it is recommended that the product information sheet be read before use, and if necessary contact be made with a specialist in the field.

If you are sailing in the Great Lakes or the Gulf Coast you may encounter maritime garter snakes. These have been seen swimming in fresh water lakes 100 meters (315 feet) or more from shore. They will also swim in salt water. The common name is broad-banded water snake and they grow to between 22 and 36 inches—a record is 45 inches. They can be found from extreme southern Illinois to central Texas and the Gulf Coast. These snakes are not dangerous.

Snakebite Symptoms

Sea snakes are all Indo-Pacific and most are venomous. Symptoms are attributable to multiple organ systems, with neurological symptoms predominating. They may occur as early as five minutes or as late as eight hours following the bite, but usually occur within two hours. If you're bit by a sea snake, here's how you can connect what actually might be going on with what you're seeing.

NeurologicalPhysical
EuphoriaFang marks, usually two or more small circular dots, may be difficult to identify
Anxiety Local reaction is usually absent or minimal
MalaiseParalysis, usually ascending
Drowsiness or mild confusionHyporeflexia (A diminished function of the reflexes), progressing to loss of reflexes
HeadacheHypersalivation
Myalgias,(inflammation of muscle tissues) which are worse with movement, usually begin in the bitten extremity and neck 30-60 minutes after envenomation Trismus (contraction of the muscles of mastication, grinding teeth)
Arthralgias, (diseases and injuries that affect human joints) Bulbar paralysis (affecting spinal cord, brain function)
Ptosis (drooping of the upper eyelid)Dysarthria, slurred speech
Mydriasis (Pronounced or abnormal dilation of the pupil) with sluggish light reaction Respiratory distress or respiratory failure
Ophthalmoplegia (Paralysis of ocular muscles), leading to double visionTachypnea (Abnormal rapidity of respiration)
Failing vision (usually a terminal symptom) Cyanosis (A blue, gray, slate, or dark purple discoloration of the skin)
Sialorrhea (Excessive secretion of saliva) Apnea (Temporary cessation of breathing)
Facial paralysis Cardiac arrest
Muscle paralysis, usually ascending; may be flaccid or spastic Fever (variable)
Dyspnea (labored or difficult breathing)Lymphadenopathy (nodes draining bite site)
Nausea, vomiting, abdominal pain and cramping  
Oliguria(Diminished urination) 
Change in urine color  
Causes
Occupational exposure: usually fishermen handling nets
Accidental exposure: stepping on sea snakes in shallow water
Nonaccidental exposure: intentionally handling sea snakes (e.g., home aquariums)




Suggested Reading:

Critters Aboard by Mark Matthews

Rayo Bravo by Mark Matthews

Medical Lessons from a Brush with Death by William Mahaffy

 

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