Poison Apparatus and Biting Mechanism in Snakes

Comparison of Non-Poisonous and Poisonous Snakes

Non-Poisonous Snakes

• Head Structure: The head is typically rounded or elliptical in shape.

• Fangs: These snakes do not possess fangs ($0$ fangs).

• Pupils: They exhibit a roundhead or round pupil shape.

• Anal Plate: Characterized by a double row of subcaudal plates.

• Bite Marks: The bite mark pattern consists of a row of small teeth marks.

Poisonous Snakes

• Head Structure: The head is usually triangular or broadened posteriorly (triangle-shaped).

• Fangs: Specific fang structures are present ($2$ long fangs).

• Pupils: They exhibit an elliptical pupil shape.

• Anal Plate: Typically characterized by a single row of subcaudal plates.

• Bite Marks: The bite mark clearly shows distinct fang marks.

• Additional Features: Some species may feature a pit (e.g., pit vipers) or a rattle (e.g., rattlesnakes).

Classification of Poisonous Snakes by Venom Secretion

Poisonous snakes are categorized into three primary families based on the nature of the poison they secrete:

• Elapidae: These snakes secrete neurotoxic venom, which primarily affects the nervous system.

• Viperidae: These snakes secrete vasculotoxic venom, which affects the blood and vascular system.

• Hydrophidae: These snakes secrete myotoxic venom, which targets muscle tissue.

Family Elapidae (Neurotoxic Snakes)

Common Cobra

• Local Names: Nag, Kalsap, or Naja naja.

• Geographic Distribution: Found throughout India, Burma, and Srilanka.

• Physical Features:
      - Possesses a well-marked hood.
      - Features either a single (monocellate) or double spectacle mark.

• Variants:
      - Spectacled cobra.
      - Kal nagini.
      - Monocellate Cobra ($Naja\,Naja\,Kaouthia$).

King Cobra

• Local Names: Raj Nag, Naja hanna, or Naja bangarus.

Krait Subgroups

• Common Krait: Identified as $Bangarus\,caeruleus$ or $Bungures\,Caeruleus$.

• Banded Krait: Identified as $Bangarus\,fasciatus$ or $Bungarus\,fasciatus$.

Other Elapidae Examples

• Mambas

• Tiger snake

• Death adder

• Coral snake

Family Viperidae (Vasculotoxic Snakes)

Russell' s Viper

• Local Name: Chandra Bora.

• Scientific Name: $Daboia\,russelii$.

Anatomy of the Poison Apparatus

The physiological machinery involved in the delivery of venom includes several specialized muscles and glandular structures:

• Musculature:
      - Temporalis Muscle: This is divided into the anterior part and the posterior part. It is involved in closing the mouth.
      - Digastric Muscle: This muscle is responsible for the opening of the snake's mouth.

• Glandular Structures:
      - Poison Gland: The primary storage and production site for venom.
      - Duct of Poison Gland: The tube that carries venom from the gland to the fangs.

• Oral and Nasal structures:
      - Fangs: The specialized teeth used for injection.
      - Trachea: Located near the floor of the mouth to allow breathing during swallowing.
      - Nostril: Part of the respiratory intake.
      - Sensory Groove: Specialized sensory surface for environmental detection.

The Biting Mechanism of Snakes

The process of delivering venom follows a specific sequence of mechanical actions:

1. Mouth Opening: The mouth is opened through the contraction of the digastric muscle.

2. Maxillary Rotation: The maxilla bone rotates to pivot the fangs.

3. Fang Erection: The fangs become erect, moving into a position where they can press into the victim.

4. Mouth Closure: The action of the temporalis muscles closes the mouth onto the target.

5. Injection: The injection of poison is completed once the mechanical action of the bite is fully engaged.