Venomous Fish - Types, Toxins Produced, and Treatment

Introduction

More than 50 % of venomous vertebrates are fish. Over 1200 venomous fish are present in the ocean. The venomous fish remain a threat to divers all over the world. The most commonly affected individuals are the young adult males involved in surfing, wade-fishing, and beachcombing in the habitat of venomous fish. Venomous animals can inject venom into the body, unlike poisonous animals, which are toxic only when touched or consumed. Therefore, the treatment for venomous fish bites depends on the type of fish and its symptoms.

What Are Venomous Fish?

Venomous fish have specialized glands or spins that produce and deliver venom. Their venom can cause pain, paralysis, and even death in human beings. Examples of venomous fish include the following:

• Scorpaenidae Family - Lionfish, stonefish, and scorpionfish.

• Pufferfish (some species).

• Catfish (some species).

• Stingray (some species).

What Are the Characteristics of Venomous Fish?

Some common characteristic features of venomous fish include the following:

• The presence of venomous spines of fins can cause pain, swelling, and paralysis.

• Specialized glands producing venom are located in various body parts, including the skin, fins, and gills.

• Venom contains a variety of toxins, enzymes, and proteins.

• Some venomous fish can camouflage themselves to avoid being detected by prey or predators.

What Is Stonefish?

Stonefish are a group of venomous fish found in the coastal regions of the Indo-pacific. They can blend with their surroundings and appear like a stone or rock, hence called stonefish. It is the most venomous fish in the Scorpaenidae family.

The venomous spines are located on their dorsal fin, which can cause intense pain, swelling, and tissue damage and can be lethal to humans if left untreated.

The symptoms of a stonefish sting include:

• Sweating.

• Nausea.

• Vomiting.

• Respiratory distress.

What Is Lionfish?

Lionfish are venomous marine fish native to the Indo-pacific, Atlantic Ocean, Caribbean Sea, and Gulf of Mexico. They belong to the Pteroinae subfamily. Lionfish appear with white, red, and black stripes, long flowing fins, and venomous spines on their dorsal, pelvic, and anal fins. They are voracious predators and consume a wide variety of small fish and invertebrates. As a result, lionfish negatively impact marine ecosystems.

The lionfish's venom can cause:

• Intense pain.

• Swelling.

• Tenderness.

• Warmth at the site of the sting.

• Redness.

• Sweating.

• Muscle weakness.

• Tingling sensation.

What Is Scorpionfish?

Scorpionfish are venomous marine fish found in tropical and subtropical waters. They have spiny, brightly colored bodies similar to scorpions. In addition, scorpionfish have venomous spines on their dorsal, anal, and pelvic fins.

The symptoms of scorpionfish sting include:

• Pain.

• Swelling.

• Redness.

• Breathing difficulties.

• Paralysis.

What Are Stingrays?

Some species of stingrays are venomous and cause painful stings to humans. Some of the venomous stingrays include the following:

• Blue-Spotted Stingray - Blue spots on the back.

• Black-Spotted Stingray - Black spots on its back with a long, whip-like tail.

• Bullseye Electric Ray - Can produce electric shock in addition to venomous sting.

• Southern Stingray - Diamond-shaped body and long, whip-like tail with a venomous sting at the base.

Stingray venom can cause

• Intense pain at the site.

• Bleeding.

• Discoloration and blistering, sometimes containing blood.

• Swelling and pain in the lymph nodes near the sting site.

• Severe pain.

• Sweating.

• Swelling at the site of the sting and generalized throughout the body, particularly if the sting is on the skin of the trunk.

The wound should be cleaned and kept still to prevent the spread of the venom.

What Are Catfish?

Several species of catfish are venomous and cause painful stings to humans. The venomous catfish species include the following:

• Candiru - Also called toothpick fish.

• Redtail Catfish - They have distinctive red tails with venomous spines on their dorsal and pectoral fins.

• Striped Eel Catfish - They have long, eel-like bodies with venomous spines on their dorsal and pectoral fins.

• Walking Catfish - It is known for its ability to walk on land using its pectoral fins.

The stings can result in morbidity, and symptoms include:

• Severe pain.

• Retained foreign bodies.

• Infection.

• Respiratory compromise.

• Arterial hypotension.

• Cardiac dysrhythmias.

What Is Pufferfish?

Pufferfish, also called blowfish, are found in both saltwater and freshwater. They have the unique ability to inflate their bodies to several times their normal size. They have poisonous flesh containing tetrodotoxin which may cause paralysis and even death in humans.

What Are the Venom Components and How Do They Affect Humans?

The fish's venom contains various components, such as proteins, enzymes, and other molecules. Some of the most common components of fish venom include the following.

• Neurotoxins - These toxins affect the nervous system by blocking the flow of ions across nerve cell membranes and cause symptoms such as paralysis, respiratory failure, and even death. Examples of fish that produce neurotoxic venom include pufferfish and some species of catfish.

• Hemotoxins - These toxins affect the blood and cause symptoms such as bleeding, organ damage, and tissue necrosis. Examples of fish containing hemotoxic venom are some species of catfish and stingrays.

• Cytotoxins - These toxins affect cells and cause symptoms such as pain, inflammation, and tissue damage. Cytotoxins are found in the venom of much venomous fish.

• Cardiotoxins - These toxins affect the heart and cause symptoms such as changes in blood pressure, rhythm, and heart rate. These toxins are found in the venom of some species of catfish.

• Enzymes - Many enzymes are found in the venom of different fish. They can break down proteins and other molecules, causing inflammation and tissue damage.

What Is the Treatment for Venomous Fish Stings?

The treatment for the venomous fish sting depends on the type of fish and the severity of the symptoms, which include the following:

1. Remove any spines from the wound and rinse with clean water.

2. Hot water immersion is the first line of treatment for marine water envenomations. The patient should soak the affected limb in hot water (42 degrees Celsius) for 30 to 90 minutes.

3. Non-steroidal anti-inflammatory drugs to control pain.

4. Compressive dressings control lymphedema of the extremities.

5. Equine fab stonefish antivenom is given intravenously or intramuscularly to neutralize the scorpionfish and stonefish envenomation.

6. Tetanus and broad-spectrum antibiotic prophylaxis prevent wound infections.

7. Monotherapy for immunocompetent patients with minor wounds.

Conclusion

People should avoid risky swims at night and closer to the ocean bed, rocks, and reefs to prevent possible envenomation of venomous fish. In addition, protective wears, puncture-proof gloves, and guards are necessary to prevent injuries from the spines of venomous fish. Marine envenomations may lead to consequences such as necrotic ulcers, persistent pain, chronic neuropathy, and morbidity if not handled efficiently.