Introduction to Venomous Mechanisms

Overview of Venoms
  - Venoms are modified forms of biological substances (e.g., hormones, enzymes) that, when enhanced, can act detrimentally to other organisms.
  - Examples of substances that can be turned into venoms:
    - Hormones (e.g., vasodilators)
    - Enzymes (e.g., digestive enzymes)
Vasodilator Example
- C-type natriuretic peptides: Used in contexts that lead to blood pressure problems when misused in a biological system.
Digestive Enzymes
- Enzymes that break down lipids and saccharides can be injected, resulting in digestion beginning prematurely within the host.
- Spider Venom Comparison: Many spider venoms contain digestive enzymes to break down prey internally.
Elapids (Highly Venomous Snakes)
- Example: Cobras, vipers
- Regions of concern: Australian elapids, known for a range of venom types, including those that induce coagulation.

Clotting Factor X
  - Integral to the coagulation cascade which helps in forming fibrin clots.
  - Activation of clotting factors inappropriately leads to disseminated intravascular coagulation (DIC).
  - DIC Characteristics:
    - Causes widespread clotting within the bloodstream leading to traffic jams (thrombosis) in vascular systems.
    - Results in severe complications such as stroke-like symptoms due to lack of blood flow to tissues.
Conditions Leading to DIC
- Severe crush injuries, severe allergic reactions.
- Venom-induced DIC can happen with inappropriate activation of the coagulation pathways.

GLP-1 (Glucose-like peptide-1)
- A hormone released to signal satiation and stimulate insulin release when food is ingested.
- In Gila monsters, a more potent form of GLP-1 is secreted, causing insulin spikes that can lead to metabolic imbalances.
Clinical Application
  - Gila monster venom was explored in the 1990s to create medications for diabetes control:
    - Bieta: A medication developed from Gila monster venom; less effective than newer alternatives.
    - Semaglutide (Ozempic): A longer-lasting GLP-1 analogue developed from Gila monster venom resulting in improved insulin control over extended periods.

Poison vs. Venom vs. Toxin
  - Poison: Generally refers to substances that need to be ingested (e.g., foods or plants).
  - Venom: Typically refers to substances delivered via a bite or sting; usually more offensive.
  - Toxin: A broader term that can include any biological poison; often used interchangeably.
Examples:
  - Poison Dart Frogs: Defense mechanism; can be toxic when consumed.
  - Destroying Angel Mushroom: Highly poisonous, causes death from liver failure.
  - Fugu: A type of pufferfish containing a potent neurotoxin.

The Concept of LD50
  - Definition: The dose required to kill half of the population receptor (or subjected) to the substance.
  - Importance: It provides a quantitative measure of a substance's acute toxicity.
  - Higher LD50 values indicate lower toxicity, while lower values indicate higher lethality.
Comparative LD50 Values:
- Gila Monster LD50: Approximately 1.4 mg/kg.
- Inland Taipan (most venomous snake): LD50 as low as 0.025 mg/kg—extremely dangerous due to minimal dose needed for fatality.

Critical Factors:
  - Volume of venom injected
  - Delivery method (e.g., fangs, size of puncture)
  - Location of bite (e.g., limb vs. torso)
  - Presence of bacteria/infection risk
  - Response of individual (varying human physiology)
Other Forms of Venom Delivery:
- Venoms can have complex delivery mechanisms, including through specialized fangs that deliver venom effectively into prey.

Antivenom Creation:
- Involves immunizing large animals (often horses) with small doses of venom to produce antibodies against the venom.
- Over time, antibodies are harvested from the animal's blood to create antivenom for human use.
Potential Side Effects of Antivenom:
- Serum sickness: Resulting from developing antibodies against horse proteins, leading to immune complex formations.
Risks for Snake Milkers:
- Encountering necrotic venom can lead to serious injuries during extraction practices.
- Handling venomous species poses risks of accidental bites, resulting in varying injury severity.

Slow Loris: Has venomous bites due to a venom gland on its elbows, which it licks and applies to its teeth.
Voles and Platypuses: Among mammals, exhibit venomous properties, particularly for defense and male competition.
Non-reptiles with Venom: Certain amphibians (e.g., ribbed newts) exhibit venomous traits, showcasing diverse evolutionary adaptations across species.

Venom has evolved in many species primarily as a means of prey capture or defense.
Various anatomical adaptations (e.g., fangs, delivery systems) demonstrate the biological complexity of venom systems across organisms, reflecting evolutionary processes.
Venom in Fish: Many bony fish have developed poisonous structures as a defense mechanism, enhancing their survival.
Venom in Reptiles: Predominantly found within squamates; venom production likely arose as a competitive adaptation against prey species.