• Snakes, belonging to the limbless group called Ophidia, are reptiles of the class Reptilia under the phylum Chordata. While the majority of snakes are non-poisonous, there are four poisonous genera of snakes. In India alone, approximately 30,000 people lose their lives to snakebites each year. Snakes have a unique way of consuming their prey, as they do not chew their food but instead swallow it whole. However, only the poisonous snakes possess a specialized poison apparatus in their heads, which sets them apart from their non-poisonous counterparts. This poison apparatus consists of a toxic substance known as venom or poison.
• It is important to understand the distinction between poison and venom. Both substances are toxic in nature, but their effects differ. If a plant or animal produces a toxic reaction when consumed, it is considered poisonous. On the other hand, when a venomous animal injects a substance into the body of its prey or an organism, it is called venom. Snakes with a poison apparatus are capable of injecting venom into their victims.
• Snakes, as a specialized group of reptiles under the order Ophidia, comprise approximately 3,000 species found primarily in tropical and subtropical regions worldwide. Out of these species, around 300 are poisonous. The skulls and jaw bones of poisonous snakes are highly flexible, allowing them to adjust accordingly during swallowing or biting. This flexibility enables their jaws to stretch wide, accommodating their prey.
• The position of fangs varies among different snake species. Cobras, for instance, have erect fangs, while in vipers, the fangs lie against the roof of their mouths when closed. The biting mechanism of snakes serves two primary purposes: the erection of fangs and the injection of venom or poison into the victim’s body.
• In conclusion, snakes possess a specialized poison apparatus in their heads, which distinguishes them as poisonous snakes. Their flexible skulls and jaws allow for efficient swallowing and biting. The biting mechanism of snakes serves to erect their fangs and inject venom or poison into their prey. Understanding the poison apparatus and biting mechanism of snakes is crucial for comprehending the nature and effects of snakebites.

Poison Apparatus of Snake

Poisonous apparatus of snakes include the following parts;

1. A pair of poison glands
2. Poison ducts
3. Fangs
4. Muscles

1. Poison Glands

• The poison apparatus of snakes consists of various components, including a pair of poison glands, their ducts, and a pair of fangs. In poisonous snakes, the poison glands are located on either side of the upper jaw. These glands are believed to be either the superior labial glands or parotid glands.
• Each poison gland has a sac-like structure and is equipped with a narrow duct at its anterior end. Within the gland, vascular fibrous septa form capsules that separate the glandular substances into secretory pockets. The duct extends forward along the side of the upper jaw and loops over itself just in front of the fang. It then opens either at the base of the fang or at the base of the tunnel within the fang.
• To maintain its position, the poison gland is held in place by ligaments. An anterior ligament connects the anterior end of the gland to the maxilla, while a posterior ligament extends between the gland and the quadrate bone. Additionally, fan-shaped ligaments are present between the side walls and the squamoso-quadrate junction.
• The poison glands are situated on both sides of the upper jaw, possibly originating from modified superior labial or parotid glands. In the case of Naia naja, for example, the gland is almond-shaped and comparable in size, surrounded by a thick capsule of fibrous tissue.
• In vipers, the poison gland is typically larger and tubular in shape, although the exact shape may vary among different genera. The gland’s capsule contains vascular fibrous septa, creating secretory pockets known as “Poison lakes of Bobeau.” By examining the section of the poison gland, the true structure of an exocrine gland can be observed.
• In summary, the poison glands are crucial components of the snake’s poison apparatus. These glands, along with their associated ducts and fangs, allow venomous snakes to inject venom into their prey or potential threats. Understanding the structure and function of poison glands provides valuable insights into the mechanisms behind snake venom production and delivery.

2. Poison Ducts of Snakes

• The poison glands in snakes are connected to a narrow duct located at the anterior end of the gland. This duct runs forward along the side of the upper jaw and forms a loop just in front of the fang. The opening of the duct can be found either at the base of the fang or at the base of the tunnel within the fang itself.
• Interestingly, the duct does not directly open at the tip of the fang but rather in a pocket of a mucous sheath that covers the basal part of the fang. This arrangement allows for more controlled and precise delivery of the venom during a bite.
• In the case of spitting cobras, such as Naja nigricollis, the poison duct undergoes a modification. It develops an “L” shaped bend just prior to exiting the fang, and the discharge orifice is located on the front surface of the fang. This adaptation enables spitting cobras to accurately project their venom over a distance, providing them with a unique defensive mechanism.
• Understanding the structure and function of the poison ducts in snakes is essential in comprehending the venom delivery system. The intricate design and precise control of venom release highlight the evolutionary adaptations that venomous snakes have developed for efficient prey capture and defense.

3. Fangs

Fangs are specialized teeth found in certain species of snakes that have evolved to inject venom into their prey. These elongated, curved, sharp, and pointed teeth serve as a mechanism for delivering venom during a snake’s predatory or defensive behavior.

There are three main types of fangs based on their structure and position within the snake’s mouth.

1. Proteroglyphous Fangs (Proto = first, glyph = hollowed): These fangs are small, grooved, and permanently erect at the front end of the maxillae, which are the upper jawbones of the snake. Cobras, kraits, coral snakes, and sea snakes possess this type of fangs. The groove in these fangs allows venom to flow into the prey.
2. Opisthoglyphous Fangs (Opistho = behind): Opisthoglyphous fangs are also small and grooved, but they are located at the posterior end of the maxillae. These fangs are associated with a groove on the posterior surface and can deliver venom when the snake bites and chews its prey. Vine snakes, common cat snakes, flying snakes, and certain rear-fanged snakes like the South African boomslang fall into this category.
3. Solenoglyphous Fangs (Solen = Pipe): Solenoglyphous fangs are large, hollow, and situated at the front of each maxilla in vipers and rattlesnakes. These fangs have a narrow hollow poison canal with an opening at the anterior end. Unlike the other types, these fangs are movable and can be folded against the roof of the mouth when the jaws are closed. This type of fang acts as a hypodermic syringe, injecting venom deep into the tissues of the snake’s victim.

The venomous fangs of snakes are modified maxillary teeth that can regenerate if lost. The base of the fangs contains an intake aperture for venom and a sub-terminal discharge aperture for delivering the venom into the prey.

Some specific adaptations can be found in certain snake species. For example, in spitting cobras and the South African ringhals, the discharge orifice is smaller, which increases the force of venom when they spray it at their targets. In Viperidae snakes, there is typically a single large poison fang on the maxilla, accompanied by smaller fangs at its base.

The structure and position of the venom canals determine the types of fangs in snakes:

1. Proteroglypha: These fangs are relatively non-movable and positioned at the front of the maxillary bone. They feature an open groove on the anterior surface and are found in cobras, kraits, mambas, and sea snakes.
2. Solenoglypha: These fangs are long, hollowed, and located at the rear end of the maxillary bone. They can move vertically and fold against the roof of the mouth when the jaws are closed. The fangs of pit vipers and true vipers fall into this category, enabling them to deliver venom deep into their prey.
3. Opisthoglypha: These fangs have an open groove on the posterior surface and are situated at the posterior extremity of the maxillary bone. They can be single or in pairs, accompanied by smaller teeth at the front. Snakes such as vine snakes, common cat snakes, flying snakes, and egg-eating snakes fall into this category. While their bites are usually not lethal to humans, the South African boomslang is an exception. Opisthoglyphous snakes’ bites may be lethal to lizards and occasionally birds, mice, and rats.

In conclusion, fangs are specialized teeth found in venomous snakes that have evolved to inject venom into their prey. They come in different types, such as proteroglyphous, opisthoglyphous, and solenoglyphous, each with specific adaptations and venom delivery mechanisms. These fangs play a crucial role in the hunting and defense strategies of venomous snakes.

4. Muscles

Muscles play a crucial role in the functioning of a snake’s venomous apparatus. Specifically, there are three types of muscles associated with the poison apparatus:

1. Digastric Muscle: This muscle is attached to the squamosal bone of the skull at one end and the articular bone of the lower jaw at the other end. Its primary function is to aid in opening the jaws of the snake.
2. Sphenopterygoid Muscle: The sphenopterygoid muscle is attached anteriorly to the spheroidal region and posteriorly to the dorsal surface of the pterygoid bone. It assists in pulling the pterygoid bone forward.
3. Anterior and Posterior Temporalis Muscles: These muscles are attached to the side walls of the cranium (skull) and the lower jaw. They are responsible for closing the lower jaw of the snake.

The positioning and action of these muscles are essential for the proper functioning of the snake’s venomous apparatus. They work in coordination with other structures such as ligaments and glands. For example:

• Ligaments: Ligaments hold the poison gland in position, extending from the maxilla-lacrimal junction to the pterygoquadrate region.
• Fan-shaped Ligaments: Fan-shaped ligaments are present along the sides of the poison gland, providing support and stability.
• Associated Muscles: In addition to the aforementioned muscles, the protractor-pterygoid muscle, located near the poison gland, and the masseter muscle (anterior and posterior temporalis), play a role in the biting mechanism.

The temporalis muscle, which has a fan-like shape and originates from the post-frontal and parietal ridges, envelops a significant portion of the poison gland. Its sudden contraction aids in ejecting venom from the gland and also helps control the biting mechanism.

The digastric muscle arises from the squamosal and quadrate junction and attaches to the articular bone of the lower jaw. Contraction of these muscles assists in opening the snake’s mouth by depressing the lower jaw.

The sphenopterygoid or protractor-pterygoid muscle arises from the anterior margin of the basal orbitosphenoid region and inserts into the dorsal side of the pterygoid bone. Its action results in pushing the ectopterygoid bone, causing rotation of the maxilla and erection of the fang.

Lastly, the anterior temporalis muscle serves as the closing muscle of the mouth. It originates from the pterygoid bones of the upper jaw and inserts into the articular region of the mandible. This muscle is responsible for closing the snake’s mouth.

In summary, the muscles associated with the snake’s venomous apparatus, including the digastric, sphenopterygoid, and anterior/posterior temporalis muscles, play crucial roles in the opening, closing, and biting mechanisms of the snake’s jaws, facilitating the efficient delivery of venom during predation or defense.

Structural elements of the skull

The structural elements of the skull in snakes are arranged in a manner that facilitates the functioning of the poison apparatus and the erecting of the fangs during a strike. Here are the key bones associated with the activation of the poison apparatus:

1. Maxilla: The maxilla is a paired irregular bone that forms the larger anterior part of the upper jaw. It is in the maxillae that the fangs are located. These fangs are specialized teeth that deliver venom to the snake’s prey.
2. Pterygoid: The pterygoid is a paired irregular bone that loosely joins with the quadrate bone at its posterior end and with the palatine bone at its anterior end. It is also a part of the alisphenoid bone.
3. Ectopterygoid or Trans-palatine: The ectopterygoid, or trans-palatine bone, is a small bone that extends from the pterygoid and joins with the maxilla. It plays a role in the structure and function of the palate.
4. Quadrate: The quadrate bone is a large, rod-like bone that is highly movable (streptostylic). It is located at the posterior end of the upper jaw. The anterior part of the quadrate bone joins with the squamosal bone, while the posterior part articulates with the lower jaw (mandible). The articulation between the mandible and the skull is facilitated by ligaments, and the mandibular rami (jawbones) are also connected by ligaments.

One peculiar feature of the snake skull is that all the bones are loosely attached and connected by elastic ligaments. This allows each bone to move independently, contributing to the flexibility and mobility of the skull. This mobility is crucial for the snake to erect its fangs efficiently during a strike.

In summary, the structural elements of the snake’s skull, including the maxilla, pterygoid, ectopterygoid, and quadrate bones, are responsible for facilitating the movement of the poison apparatus and the erecting of the fangs. The loosely attached nature of the bones allows for independent movement, acting as a lever system to assist in the efficient delivery of venom during predation or defense.

Biting mechanism

The biting mechanism of poisonous snakes involves several coordinated movements that can be divided into four distinct phases: the strike, opening of the mouth and elevation of the fangs, closing of the jaws and injection of venom, and retraction of the fangs.

1. The strike: During this phase, the snake rapidly propels itself forward towards its prey or target. Vipers exhibit greater velocity in their strikes compared to colubrids. Some hooded snake species raise their heads from the ground, compensating for the limited mobility of their fangs.
2. Opening of the mouth and elevation of the fangs: Most poisonous snakes begin the strike with closed jaws. As the head approaches the target, the mandibles are depressed by the rapid contraction of specific muscles, including the digastrics, cervicomandibular, and vertebro-mandibular muscles. Simultaneously, the fangs are elevated or rotated forward through the contraction of the sphenoand parieto-pterygoid muscles. The lower jaw moves down, and the quadrate bone, which is highly movable, pushes the pterygoid bone forward. This movement of the pterygoid bone, transmitted by the trans-palatine bone to the maxilla, causes the maxilla to rotate about 90 degrees, carrying the fang forward and ventrally. The sphenopterygoid muscles also contribute to the forward movement of the pterygoid.
3. Closing of the mouth and injection of venom: Following the opening of the mouth and elevation of the fangs, the jaws close. This closure is facilitated by the simultaneous contraction of the anterior, middle, and posterior temporal muscles, which strongly elevate the mandibles. In colubrids, the venom gland is compressed by the superior and inferior portions of the anterior temporal muscles, leading to the expulsion of venom from the gland along the duct. In vipers, the muscle arrangement acting on the venom gland differs, and the expulsion of venom is instantaneous and independent of the fixation of the lower jaw.
4. Retraction of the fangs and insertion of venom: After the fangs have been inserted into the target and venom has been injected, the retractor muscles responsible for operating the pterygo-palatine-transverse arch contract. This contraction drags the elevated fangs downwards and backwards through the tissues. The squeezing action of the contracting muscles on the poison gland forces the venom into the groove or channel of the fangs. The entire process, including the injection of lethal doses of venom, occurs rapidly and in a coordinated manner.

The skull and jaw bones of poisonous snakes are characterized by loose and movable articulations, allowing for an enormous gape and the swallowing of large prey. The premaxilla, bones of the upper jaw, and lower jaw halves are loosely attached, and there are movable joints between various bones of the skull, brain case, palate, and jaws. These joints have loose ligaments, enabling movement in multiple directions and facilitating a wide jaw separation.

In summary, the biting mechanism of poisonous snakes involves a sequence of coordinated movements, including the opening and closing of the mouth, the elevation and retraction of the fangs, and the injection of venom. The mobility and loose articulations of the skull and jaw bones play a crucial role in enabling the snake to strike, capture prey, and deliver venom effectively.

Nature of Venom

Snake venom is a highly evolved saliva that serves two main purposes for snakes: killing their prey and aiding in digestion. There are two types of snake venom: neurotoxic venom found in cobras and kraits, which affects the nerves, and hemotoxic venom found in vipers, which affects the blood.

Here are some characteristics and properties of snake venom:

1. Appearance and density: Snake venom is a clear, transparent, pale yellow, or straw-colored fluid with a specific gravity ranging from 1.03 to 1.07.
2. pH: The pH of snake venom varies among species. For example, the pH of Russell’s viper venom is 5.8, while cobra venom has a pH of 6.6.
3. Composition: Venom is primarily protein-based and contains various enzymes such as proteinase, hyaluronidase, L-arginine hydrolases, transaminase, L-amino acid oxidase, phospholipases (A, B, and C), phosphodiesterase, cholinesterase, ribonuclease, deoxyribonuclease, alkaline phosphatase, acid phosphatase, and exopeptidases. The exact composition of venom varies between snake species.
4. Taste: Most snake venoms are tasteless, but cobra venom has a slightly bitter taste.
5. Solubility: Snake venom is soluble in both water and glycerin. It is acidic in reaction.
6. Stability: Venom is susceptible to destruction by coagulating agents such as KMnO4, AgNO3, as well as alcohol and strong alkalies like NaOH and KOH.
7. Metal content: Snake venom may contain metals such as zinc (Zn), sulfur (S), copper (Cu), among others.
8. Protein content: Venom contains several active non-enzymatic proteins, typically consisting of at least two or three peptides.
9. Thermolability: Venom is sensitive to heat and is considered thermolabile.
10. Drying: Venom can be dried to form crystals or lyophilized. Dried venom exhibits thermostability.
11. Digestive properties: Snake venom possesses potent digestive enzymes, enabling snakes to easily digest their prey. However, venom should not be ingested if there are wounds in the buccal cavity or alimentary canal.

Overall, snake venom is a complex mixture of proteins and enzymes that varies in composition, affecting either the nerves or the blood of the snake’s prey. Its properties and components are well-adapted to fulfilling the snake’s predatory and digestive needs.

Effects of Poison

When a snake injects venom into a human, the effects can vary depending on the species of snake and the type of venom. Here are the effects of snake venom based on the information provided:

1. Cobra Poison: The effects of cobra venom are typically observed within half an hour after a bite. Symptoms include giddiness, a high pulse rate, excessive salivation, partial paralysis of the tongue and larynx, vomiting, and pupil constriction. The eyes remain sensitive to light, and consciousness is undisturbed initially. However, respiration becomes shallow and eventually ceases, leading to death. Cobra venom acts as a neurotoxin, affecting the nervous system.
2. Viper Poison: The effects of viper venom are usually observed within a quarter of an hour after a bite. Symptoms include swelling of the bitten area, discoloration due to extravasation (leakage of blood into the surrounding tissues), intense burning pain, dilated pupils, a high pulse rate, profuse vomiting, and watery discharge from the rectum. Sensitivity to light decreases, and consciousness is affected. Extravasation spreads, causing extensive swelling, and ultimately leading to death. Viper venom is considered haemo-toxic, affecting the blood.
3. Krait Poison: Kraits are highly venomous, but the absence of local pain, swelling, oozing, or bleeding can initially raise doubts about a krait bite. Fang marks may not be visible. The symptoms of krait envenomation are similar to the neurotoxic effects of cobra venom. The first sign is ptosis (drooping of the eyelids). Other signs include severe abdominal pain, drooling of saliva, cyanosis (bluish discoloration of the skin), and respiratory failure. Krait venom acts as both a neurotoxin and a haemo-toxin. The cause of death is asphyxia resulting from paralysis of the respiratory center.
4. Sea Snake’s Poison: Sea snakes are highly venomous, and their venom acts as a myotoxin, affecting the muscles. The initial symptoms include weakness and soreness in the muscles. The eyelids droop, and the jaws become stiff. Weakness progressively worsens to the point where the patient may be unable to move a finger. The muscles are damaged, releasing myoglobin, which is excreted through the kidneys and can cause the urine to turn red. Irregular heartbeats may occur, and death can happen within 12 hours after the bite. In some cases, death may be delayed by several days.

It is important to note that the effects of snake venom can vary, and prompt medical attention is crucial in all cases of snakebite to receive appropriate treatment and antivenom if necessary.

Anti-Snake Venom Serum

• Anti-snake venom serum is an essential medical resource used to treat snakebite victims. In India, the production of anti-snake venom serum takes place primarily at the Hoffkine Institute in Mumbai and the Central Research Institute in Kasauli, Himachal Pradesh.
• The process of preparing anti-venom involves immunizing horses. A combination of venom from four common poisonous snakes found in India, namely the Cobra (Naja naja), Common Krait (Bungarus caeruleus), Russell’s viper (Vipera russelli), and Saw-scaled viper (Echis carinatus), is injected into the horse’s body. Initially, a small dose of venom is administered, which is gradually increased over time. This exposure triggers the horse’s immune system to produce antibodies against the venom.
• Once the horse has developed a sufficient level of immunity, its blood is drawn to collect the plasma, which contains the desired antibodies against the snake venom. The plasma is processed and packaged in 10 ml doses for distribution and use in treating snakebite victims.
• It’s important to note that not all types of anti-venom are produced in India. For example, anti-venom for the Banded Krait, King Cobra, and Sea Snake is not manufactured in the country. The closest source for these specific types of anti-venom is the Queen Saovabha Institute in Bangkok, Thailand.
• Anti-snake venom serum plays a crucial role in the treatment of snakebite cases. It works by neutralizing the toxic components present in snake venom, thereby preventing or minimizing the harmful effects on the human body. Rapid administration of the appropriate anti-venom is vital to counteract the effects of snakebites and improve the chances of recovery for the affected individuals.

Treatment of a Poisonous Snake Bite

Treatment of a poisonous snake bite requires immediate attention and proper medical care. The following methods are recommended for the victims:

1. Stop the spread of venom: Apply a tourniquet or ligature about 5 to 10 cm above the bite site, in the direction of the heart. This helps prevent the venom from spreading further into the body.
2. Clean the wound: Wash the bite area with clean water to remove any dirt or debris.
3. Make an incision: With a sterilized knife or blade, make a shallow incision about 1 cm deep near the wound. This incision helps in the local release of venom.
4. Apply pressure and suction: Apply pressure around the wound to help release some blood, and use a suction cup to extract a small amount of blood. Never suck out the venom with your mouth, as it may introduce harmful bacteria and further complications.
5. Keep the victim relaxed: Provide reassurance and keep the victim in a calm and relaxed state. Stress and anxiety can worsen the symptoms.
6. Seek medical help: Immediately seek medical attention from a healthcare professional. They will be able to administer appropriate treatment, including antivenom.
7. Administer antivenom: The physician will inject antivenom, also known as antivenin, to neutralize the venom. The exact dosage of antivenom required can range from 10-100 ml, depending on the severity of the bite and the type of snake involved.
8. Monitor and manage complications: The medical team will closely monitor the patient for any complications associated with the antivenom. These may include fever, allergic reactions, or severe shock conditions such as anaphylactic shock caused by the release of histamines. Prompt medical intervention is necessary to address these complications.
9. Handle the victim carefully: It is important to handle the snakebite victim with caution, as general handling can increase blood circulation and potentially spread the venom faster throughout the body.
10. Polyvalent serum for specific snake bites: In the case of bites from cobras, kraits, or vipers, the administration of polyvalent serum is preferred, preferably through intravenous injection, as soon as possible after the bite. In some cases, a placebo injection may be recommended to provide reassurance to the patient.

It is crucial to remember that these steps are general guidelines, and the specific treatment may vary depending on the severity of the snakebite and the availability of medical resources. Seeking immediate medical attention should always be the priority in cases of snakebite.

Indian Poisonous Snakes and Venom

India is home to several species of highly venomous snakes. Here are some details about specific Indian poisonous snakes and their venom:

• Common Krait (Bungarus caeruleus): The common krait is considered the second most poisonous snake in the world and the most poisonous in Asia. Its bite can be fatal to humans. The venom of the common krait is more toxic than that of the cobra, with a potency estimated to be 15 times greater than cobra venom. The venom yield per strike varies from 8 to 2 mg of dried venom. A dose of 1 mg of dried venom can be lethal to humans, and death may occur within 5 to 12 hours after the bite.
• Banded Krait (Bungarus fasciatus): The banded krait is also highly venomous, and its bite is considered lethal. Although there are few recorded incidents of bites by this species, the venom is less toxic than cobra poison. However, there are reports of a bullock dying within approximately 20 minutes after being bitten by a banded krait.
• Indian Cobra (Naja naja): The Indian cobra is one of the most well-known venomous snakes in India. It can secrete approximately 211 mg of venom per strike. A dose of 12 mg of venom is considered lethal for a human. The venom glands of the Indian cobra contain about 317 mg of venom. The venom of the cobra is five times more virulent than that of the viper.
• King Cobra (Ophiophagus hannah): The king cobra is the world’s longest venomous snake and possesses a formidable venomous bite. Although its venom is less virulent than that of the cobra, a single bite can deliver a dose of venom equivalent to ten lethal doses for a human. Death from a king cobra bite has been recorded in as little as 15 to 20 minutes. The venom glands of the king cobra can yield approximately 650 mg of venom. Even large animals like adult elephants can succumb to a single bite from a king cobra.
• Russell’s Viper (Vipera russelli): Russell’s viper is a highly venomous snake found in India. It can inject about 72 mg of venom per strike. A dose of approximately 15 mg of venom is considered fatal for a human. The fangs of Russell’s viper are the longest among Indian poisonous snakes, measuring about 16 mm. The venom gland contains approximately 108 mg of venom.
• Saw Scaled Viper (Echis carinatus): The saw-scaled viper is a small but extremely venomous snake. The average yield of dry venom by weight is about 18 mg, with a maximum recorded yield of around 72 mg. Approximately 12 mg of venom can be injected per strike. A dose of 8 mg is believed to be fatal for a human. The venom of the saw-scaled viper is five times more virulent than that of the cobra and 16 times as toxic as Russell’s viper venom. The fangs of the saw-scaled viper measure about 5 mm in length, compared to a body length of approximately 380 mm.

It is important to exercise caution and seek immediate medical attention in the event of a snakebite, as the venom from these species can have severe effects on human health and may require specific anti-venom treatment.

FAQ

References

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