How do sea snakes differ from land snakes. What makes sea snake venom so potent. Why are sea snake bites rarely fatal despite their highly toxic venom. How have sea snakes adapted to aquatic life. What is the mechanism of action for sea snake neurotoxins.

The Remarkable World of Sea Snakes: An Overview

Sea snakes, members of the family Hydrophiidae, are a group of fascinating marine reptiles that have adapted to life in aquatic environments. These serpents are closely related to the Elapidae family, which includes cobras, and share similar fang structures. Unlike their terrestrial counterparts, sea snakes have evolved to spend most or all of their lives in marine habitats, primarily in the tropical waters of the Pacific and Indian Oceans.

With approximately 52 species identified, sea snakes exhibit a range of unique adaptations that set them apart from land-dwelling snakes. Their flattened, oar-like tails enable efficient propulsion through water, while specially positioned nostrils and salt glands help them navigate their marine environment.

Key Characteristics of Sea Snakes

• Flattened, paddle-like tail for swimming
• Nostrils located at the top of the snout for easy breathing at the water’s surface
• Salt glands to expel excess salt from their bodies
• Fixed, front-positioned fangs
• Highly potent venom

Sea Snake Venom: A Potent Cocktail of Toxins

One of the most intriguing aspects of sea snakes is their exceptionally potent venom. Their venom glands produce a lethal mixture of proteins and neurotoxins that is 2-10 times more potent than that of any terrestrial snake. This makes sea snakes among the most venomous creatures in the world.

Composition of Sea Snake Venom

The venom of sea snakes contains a complex mixture of components, including:

• Proteins:
  • Lecithinase
  • Anticoagulase
  • Hyaluronidase
• Neurotoxins:
  • Erabutoxin a
  • Erabutoxin b
  • Erabutoxin c

Among these components, the neurotoxins play the most significant role in the venom’s potency. They act on acetylcholine receptors, causing paralysis of skeletal muscles and potentially leading to death by respiratory arrest.

Erabutoxin b: The Deadly Neurotoxin of Sea Snakes

Erabutoxin b is the most active component of sea snake venom. This short-chain protein consists of 62 amino acids and possesses a unique structure that contributes to its potent effects.

Structure and Properties of Erabutoxin b

• 62 amino acid sequence
• 4 disulfide bridges crucial for toxicity
• Anti-parallel beta-sheet structure
• No alpha-helix structures

The primary structure of erabutoxin b is a complex sequence of amino acids, beginning with arginine at the N-terminal and ending with asparagine at the C-terminal. This specific arrangement contributes to the toxin’s ability to bind to acetylcholine receptors and exert its paralyzing effects.

Mechanism of Action: How Sea Snake Venom Paralyzes Its Victims

While the exact mechanism of erabutoxin b is not fully understood, researchers have identified its primary target: the nicotinic acetylcholine receptors at the neuromuscular junction.

The Paralysis Process

1. Erabutoxin b binds irreversibly to acetylcholine receptors on the motor end plate.
2. This binding blocks the normal function of these receptors.
3. Acetylcholine can still bind to unaffected receptors, opening ion channels and causing depolarization.
4. However, the presence of erabutoxin b creates a neuromuscular blockade between the phrenic nerve and the diaphragm.
5. This blockade leads to paralysis of the diaphragm.
6. Respiratory arrest occurs, potentially resulting in death.

This efficient mechanism explains why sea snake venom can be so deadly, even in small quantities. However, the relative rarity of fatalities from sea snake bites is due to several factors, including the snakes’ generally docile nature and their tendency to inject only small amounts of venom when biting.

Rapid Biosynthesis: The Remarkable Speed of Venom Production

One of the most astonishing aspects of sea snake venom is the incredible speed at which it is produced. Experimental studies have revealed that the biosynthesis of erabutoxin b occurs at a rate that is almost unparalleled in nature.

The Lightning-Fast Venom Production Process

Researchers used labeled isoleucine injected into sea snake venom glands to track the synthesis of erabutoxin b. The results were astounding:

• Synthesis begins just 30 seconds after injection
• The process is completed within 1 minute
• Total synthesis time: 30 seconds to 1 minute

This rapid biosynthesis allows sea snakes to quickly replenish their venom supplies, ensuring they are always prepared for hunting or self-defense.

Sea Snake Behavior and Human Interactions

Despite their potent venom, sea snakes are generally not considered as dangerous to humans as many of their terrestrial relatives. This is due to several factors related to their behavior and habitat.

Factors Influencing Sea Snake-Human Interactions

• Docile nature: Most sea snake species tend to be non-aggressive and will avoid confrontation with humans.
• Habitat: Their marine environment limits direct contact with humans, reducing the likelihood of encounters.
• Venom injection: Sea snakes often deliver “dry bites” or inject only small amounts of venom when biting defensively.
• Fang structure: Unlike some land snakes, sea snakes do not have retractable fangs and tend to “chew” rather than strike quickly.

While sea snake attacks on humans have been recorded, they are relatively rare compared to incidents involving terrestrial venomous snakes. However, it’s crucial to exercise caution and respect when encountering these marine reptiles in their natural habitat.

Adaptations for Marine Life: How Sea Snakes Thrive in Aquatic Environments

Sea snakes have evolved a suite of adaptations that allow them to flourish in marine ecosystems. These modifications to their anatomy and physiology set them apart from their terrestrial ancestors and enable them to navigate the challenges of aquatic life.

Key Adaptations of Sea Snakes

1. Paddle-shaped tail: This flattened, oar-like appendage provides efficient propulsion through water.
2. Valve-like nostrils: Located at the top of the snout, these can be closed underwater and opened at the surface for breathing.
3. Salt glands: These specialized glands allow sea snakes to excrete excess salt, maintaining osmotic balance in a marine environment.
4. Streamlined body shape: Reduces drag while swimming.
5. Enhanced lung capacity: Allows for prolonged dives.
6. Cutaneous respiration: Some species can absorb oxygen through their skin, supplementing their breathing.

These adaptations demonstrate the remarkable evolutionary journey of sea snakes, showcasing how they have become specialized for life in the ocean while retaining characteristics of their terrestrial snake ancestors.

Conservation and Future Research: Protecting Sea Snakes and Unlocking Their Secrets

As with many marine species, sea snakes face various threats in today’s changing oceans. Conservation efforts are crucial to ensure the survival of these unique reptiles. Additionally, ongoing research into sea snake biology, venom, and ecology continues to yield fascinating insights with potential applications in medicine and environmental science.

Conservation Challenges and Efforts

• Habitat destruction and degradation
• Climate change and ocean acidification
• Bycatch in fishing operations
• Pollution, particularly plastic waste

Efforts to protect sea snakes include establishing marine protected areas, implementing sustainable fishing practices, and conducting population monitoring studies. Public education about the importance and relative harmlessness of sea snakes also plays a crucial role in their conservation.

Future Research Directions

Ongoing and future research on sea snakes may focus on:

• Detailed venom analysis for potential pharmaceutical applications
• Understanding the genetic basis for rapid venom biosynthesis
• Studying sea snake adaptations to inform marine engineering and technology
• Investigating the impacts of climate change on sea snake populations and distribution
• Exploring the role of sea snakes in marine ecosystems and food webs

As we continue to unravel the mysteries of sea snakes, we gain not only a deeper appreciation for these fascinating creatures but also valuable insights that may benefit human health and our understanding of marine ecosystems. The study of sea snakes serves as a reminder of the incredible diversity of life on our planet and the importance of preserving it for future generations.

Sea Snakes

Sea Snakes

Sea
snakes come from the Family Hydrophiidae, living most or all of their lives in
usually aquatic, marine environments.  They are very closely related to the
Family Elapidae which contains “cobra” type snakes, and this is most
evident in their fang structure.  The right image shows the characteristic
small sized fangs towards the front of the mouth, which are used to envenom
their prey.  Sea snake fangs are fixed, and unlike many land based snakes,
they do not make lightning fast strikes, instead they tend to hang on and
chew.  Mmm.

Sea
snakes are typically found on tropical shores of the Pacific and Indian oceans
(luckily not the Atlantic).  This close proximity to human activity means
that there have been a range of attacks recorded although the species as a whole
is not aggressive and will usually shy away.   These snakes have evolved
special salivary glands that produce venom which functions to immobilise and
digest prey.  Their venom is one of the most deadly in the world,
containing a lethal cocktail of proteins and neurotoxins.  Sea snake venom
has been found to be 2-10 times as venomous as any terrestrial snake making them
extremely deadly, but their docile nature and relatively extreme environment
make them less dangerous than their land dwelling relatives.

Venom

The venom contains a series of proteins and
neurotoxins.

The neurotoxins are by far the most active
constituent of the venom and work by acting on the acetylcholine receptor.  
This causes paralysis of skeletal muscle and death results by respiratory
arrest.  The venom is potent, but only small amounts are usually injected
so fatalities are rare.  This is coupled with an observed reluctance to
deliver venom when they bite.

Structure

The most active component of the venom is
erabutoxin b, a short chain protein that consists of 62 amino acids.  The
primary structure can be illustrated as follows:

N-terminal-ARG-ILE-CYS-PHE-ASN-GLN-HIS-SER-SER-GLN-

PRO-GLN-THR-THR-LYS-THR-CYS-PRO-SER-GLY-SER-GLU-

SER-CYS-TYR-HIS-LYS-GLN-TRP-SER-ASP-PHE-ARG-GLY-

THR-ILE-ILE-GLU-ARG-GLY-CYS-GLY-CYS-PRO-THR-VAL

-LYS-PRO-GLY-ILE-LYS-LEU-SER-CYS-CYS-GLU-SER-GLU-

VAL-CYS-ASN-ASN-C-Terminal

Like so many other neurotoxins erabutoxin
b contains 4 disulfide bridges, which are known to be incredibly important in
the toxicity of the venom.   The neurotoxin has an anti-parallel Beta sheet
structure containing no alpha helix structures.

Erabutoxin b

Mechanism

The mechanism that erabutoxin b exerts is not yet fully
understood but it is believed to act at acetylcholine receptors.  Upon
envenomation the toxin binds to the nicotinic acetlycholine receptor on the
motor end plate blocking it irreversibly.  Acetlycholine binds to an
unaffected receptor and opens an ion channel, this results in the depolarization
of the end plate through the influx of Na⁺ ions.  If the
depolarization then causes an action potential a skeletal muscle contraction
occurs.  But in the presence of erabutoxin b there is a neuromuscular
blockade between the phrenic nerve and the diaphragm.  The diaphragm is
paralysed and death results from respiratory arrest.

Biosynthesis

The most amazing aspect of this toxin is its
biosynthesis, in that it is synthesized extremely quickly.  The rate of
biosynthesis was experimentally found by injecting labeled isoleucine into the
venom glands.  This showed the synthesis starting 30 seconds after
injection and finishing 1 minute after injection, i.e. between 30 seconds – 1
minute!  For more info.

Sea Snakes Facts and Information

Scientific Classification

Common Name

sea snakes

Kingdom

Animalia

Phylum

Chordata

Class

Reptilia

Order

Squamata

Family

Hydrophiidae (“water lovers”)

Genus Species

Approximately 52 species

Fast Facts

Description

Sea snakes can be identified by their flattened and oar-like tail. This adaptation allows sea snakes to propel themselves through the water more effectively. Other aquatic adaptations include salt glands and nostrils located at the top of their snouts to breathe more efficiently.

Size

They vary in length, with the smallest adults being 50 cm (20 in.) long, to the largest, which may exceed 2 m (6.6 ft.).

Weight

No data

Diet

Sea snakes feed mainly on fishes and fish eggs.

Incubation

Sea snakes can be oviparous (egg birth) or ovoviviparous (egg live birth), depending on the species. In ovoviviparous reproduction, the internally fertilized eggs of the female are retained in her body. The embryos soon shed their membrane and develop in the mother’s uterus

Clutch Size: Sea snakes usually have 3-4 young at a time.

Sexual Maturity

No data

Life Span

No data

Range

Sea snakes are widely distributed throughout the Indian and Pacific oceans, especially around Australia and New Guinea. Two species, Laticauda colubrina and Pelamis laturus, inhabit the coasts of the Americas.

Habitat

Found in shallow or coastal water habitats. Some species may venture on land, although most sea snakes are helpless if washed ashore.

Population

Global: No data

Status 

IUCN: One species, Crocker’s sea snake, Laticauda crockeri, is listed as vulnerable.
CITES: Not listed
USFWS: Not listed

Fun Facts

1. Sea snakes are front-fanged and highly venomous.
2. A fold in the gums of a sea snake hides the fangs, and the fangs quickly emerge when biting. Sea snake fangs are fragile and may break off and remain in the wounds of their victims. To counter the problem of having weak fangs, sea snakes have potent venom that can easily paralyze, kill, and begin the digestive process of the fish they target.

Ecology and Conservation

Generally, sea snakes are not aggressive animals – attacks on humans are extremely rare. Bites occur chiefly to fishermen who try to remove sea snakes from their nets. Also, sea snakes will defend themselves if seized or harassed.

Sea snakes are regarded as a delicacy in the Orient. Sea snakes are attracted by light, which is often the method used by humans to collect them.

Bibliography

Bauchot, Roland (ed.). Snakes a Natural History. New York: Sterling Publishing Co., Inc., 1994.

Coborn, John. The Atlas of Snakes of the World. New Jersey: T.F.H. Publications, inc. 1991.

Cogger, H.G. and R. G. Zweifel. The Encyclopedia of Reptiles and Amphibians, 2nd ed. San Diego. Academic Press. 1998.

Ernst, Carl H., and Zug, George R. Snakes in Question. Washington: Smithsonian Institution Press, 1996.

Mattison, Chris. Snakes of the World. New York: Facts on File Publications, Inc., 1986.

Mehrtens, John M. Living Snakes of the World. New York. Sterling Publishing Co., Inc. 1987.

animaldiversity.ummz.umich.edu

Crown of Evolution.

Scientists have figured out how venomous snakes got their famous fangs.

Related video

In a new study, scientists show that the changes occurred due to modifications in the structure of the teeth, which helped to fix the fangs in the sockets. In some species of snakes, channels have developed in the teeth that run through the entire canine tooth, which began to be used to inject poison, reports theconversation.com

Of the nearly 4,000 snake species, about 600 are considered medically dangerous. This means that after a bite, a person needs urgent medical attention. But many of these snakes have small fangs and are considered not very venomous. According to scientists, the appearance of not very dangerous poisons precedes the appearance of poisonous fangs in snakes.

Taipan

Photo: wikipedia

Venomous fangs of snakes vary:

• They can be placed in the back of the mouth, as in crab-eating water snakes, cat-eyes, gray tree snakes and boomslangs
• They can be placed in the front of the mouth, like in cobras, coral snakes, kraits, taipans and sea snakes
• They may also be in the front of the mouth, but may curve backwards or sideways, as in vipers and rattlesnakes.

Location of poisonous fangs in snakes

Photo: The Conversation

The History of Fangs

“If you look at the evolution of snakes, the most recent common ancestor of all snakes with fangs probably didn’t have them,” said study authors Alessandro Palchi of Flinders University, Australia, Aaron LeBlanc of King’s College London and Olga Panagiotopoulou of Monash University, Australia.

So how did snakes evolve their syringe-like fangs that evolved from the simpler, cone-shaped teeth of their ancestors?

“To answer this question, we carefully studied snake teeth and how they develop. We examined 19 species of snakes, both venomous and common, as well as one fossil snake,” the scientists say.

Taipan skull and close-up of its left canine, in longitudinal and transverse sections, showing the relationship between the plicidentin folds and the venom channel.

Photo: The Conversation

The secret of snake teeth

“We found that almost all snakes have teeth that are strongly concave at the base and look wrinkled in cross section,” scientists say.

These folds, plicidentins, occur in the layer of the tooth called dentin. Plicidentins have been found in many extinct animals and in some species of extant fish and lizards, but their purpose is not fully understood. One theory suggests that they help the tooth not break during biting.

“When we tested this theory with computer simulations, we found that it was not,” the study authors say.

Snakes change their teeth throughout their lives and their teeth are placed in shallow holes. Scientists believe that these folds improve the anchoring of new teeth in empty sockets, providing a larger area for attachment.

Scientists say that one of the folds in poisonous snakes is much larger than the others. It occupies the entire tooth, forming a channel for the passage of poison. The researchers also found that in some species of venomous snakes, such channels may exist in teeth other than fangs, but they are not associated with venom glands.

“We found a clear relationship between the presence of plicidentins and venom channels. We concluded that at the very beginning, venomous snakes accidentally developed canals in their teeth, simply as a result of an increase in plicidentins, independent of the venom glands,” the scientists say.

Cobra

Photo: wikipedia

How ordinary teeth became venomous

The scientists then investigated how snake fangs and venom glands evolved together to become an effective means of delivering venom. In the ancestors of modern venomous snakes, the presence of venom glands was a necessary condition for the transformation of teeth with channels into enlarged venomous fangs.

Scientists believe that when a tooth appeared with a canal near the exit of the poisonous gland, natural selection contributed to the increase in this tooth in size. Also, this tooth has become more effective at injecting poison.

“This evolutionary process eventually led to the large, syringe-shaped fangs that venomous snakes have today,” the scientists say.

Poisonous snakes. Questions and Answers

There are more than 2500 species of snakes in the world. Of these, only 450 species are poisonous. These include vipers, cobras, mambas, sea snakes, etc. Even poisonous snakes only attack for defense.

Why do snakes have fangs?

With the help of fangs, snakes inject poison into the victim’s body. All venomous snakes have venom glands next to their fangs. When the snake bites the prey, the muscles press on the gland, the poison passes through the hollow fangs and is injected into the body of the victim.

The viper, one of the most venomous snakes, has only one pair of fangs. But they are longer than other types of snakes

Why do cobras have shorter fangs than vipers?

Cobras and other snakes of the same family have short fangs. Unlike vipers, these snakes cannot put their teeth in their mouths when they are not using them. If the fangs were too long, the cobra would injure itself by closing its mouth.

How many types of venom do snakes produce?

There are two types of snake venoms. Asps produce neurotoxins. They affect the nervous system of the victim and lead to rapid death. Vipers produce a hemotoxin that affects the blood and organs, but does not kill immediately.

What is the difference between a pit viper and a true viper?

Both snakes belong to the same family. However, pit vipers (rattlesnakes) have special heat-sensitive organs – pits located between the ears and nostrils. These organs allow snakes to sense temperature differences between prey and surroundings, so rattlesnakes can hunt even in the dark.

The rattle of the pit viper consists of modified scales at the end of the tail. Each time a rattlesnake changes skin, a new segment is added to the rattle.

Are rattlesnakes venomous?

Rattlesnakes are very poisonous. They are found in North America and Mexico. Most species produce a very potent hemotoxic venom. Usually snakes warn of an attack by twitching their tail, which has a rattle of several connected scaly segments. When the snake twitches its tail, the segments rub against each other and make a crackling sound that repels most animals.

How have sea snakes adapted to life in the water?

Sea snakes have a paddle-shaped tail. They have a large lung that fills almost the entire body. Because of this, snakes can stay under water for a long time. Sea snakes prey on fish and small marine animals.

Sea snakes are found in warm waters, mainly off the coast of Asia and South America. Compared to other snakes, they have flatter heads, which helps them swim better

Which snake has the longest fangs?

The Gaboon viper has the longest fangs, their length can reach 5 cm.