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Updated 23 November 2010

Beware these sea creatures

Blue bottles, jellyfish and sea anemones can sting, starfish and sea cucumbers should be avoided, and sea snakes are extremely venomous. Use this guide to venomous marine animals.

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Blue bottles, jellyfish and sea anemones can sting, sea urchins, starfish and sea cucumbers should rather be avoided, and sea snakes are extremely venomous. Use this guide to venomous marine animals, compiled with the help of leading South African toxicologist Dr Gerbus Müller, before you or your kids set foot in the sea this summer.

Venomous marine animals cause injury by means of bites, stings or direct contact. The following animals can be found in local sea waters:

1. Blue bottles, jellyfish, sea anemones, fire corals and sea firs


This group of sea animals, classified as Coelenterata, refers to hollow-bodied animals often equipped with stinging cells (nematocysts). The stinging cells are usually situated on tentacles.

Several million cells may fire during contact, injecting toxins into the skin.

When you accidentally brush against a tentacle while swimming or walking on the beach, the resulting sting can be irritating or painful, and may even be dangerous.

Symptoms and signs of stings: Humans respond to the venom with a burning reaction or pain in the region of contact with the skin. A sting usually results in a linear, whip-like lesion at the area of contact.

Lesions may heal within a day or two. However, raised red lesions may develop into fluid-filled lesions or blisters and may heal with scarring and increased skin pigmentation.

Secondary bacterial infection may occur.

In rare cases, the venom affects other parts of the body (systemic reaction) and not only the region of contact. Symptoms may include widespread itching, shortness of breath, nausea, vomiting, headache, dizziness, irregular heart rate, muscle spasms and joint pain.

Treatment:

  • Rinse the affected area with copious amounts of sea water. Don't rinse with fresh water and don't rub the area – this may cause further irritation.
  • Vinegar, alcohol and human urine may help to inactivate the toxin.
  • A sharp knife, razor or even a plastic card can be used to shave or scrape the affected area in an effort to remove the remaining nematocysts.
  • A hot bath for 30 minutes may alleviate the symptoms.
  • Topical steroids applied at the site of the sting can be used to treat pain.
  • Seek medical attention when you begin to develop persistent muscle spasms, have difficulty breathing or develop a secondary bacterial infection.

How to prevent stings: Check where the nearest doctor or hospital is before you and your family spend the day at the sea.

Always be an alert swimmer and watch out for possible dangers. Lightweight protective clothing, a wetsuit or a layer of petroleum jelly spread on bare skin can help protect you against stings when swimming.

Before you venture into the water, check with other swimmers or lifeguards to find out if some of these marine animals are a problem in that particular area.

2. Sea urchins, starfish and sea cucumbers


This group of venomous marine animals are collectively classified as Echinodermata.

The brittle spines of most sea urchins are non-venomous, but they can easily penetrate the skin.

The flower urchin is the most venomous of all local sea urchins, whereas the long-spined needle urchin causes the most serious injuries.

Symptoms and signs of injury: Piercing of the skin may result in intense burning, pain and swelling. At times, heavy bleeding may occur.

Raised, fleshy lesions may still be present several months after the initial injury.

Treatment:

  • Immerse the affected area in a bowl or basin filled with very hot water.
  • Use a local anaesthetic or topical calamine lotion to treat inflammation of the skin.
  • Seek medical attention if the urchin spines do not dissolve. Surgical removal of the spines may be necessary.

How to prevent injury: Check where the nearest doctor or hospital is before you and your family spend the day at the sea.

Always be an alert swimmer and watch out for possible dangers. Wear a pair of slipslops when you venture into a tidal pool or swim in a rocky area.

Also don't touch rocky surfaces with your hands – especially if you can't see clearly underneath the water. A pair of goggles may help you to identify and avoid sea urchins below water.

Wear protective gloves when you're searching for sea delicacies, like mussels or abalone, among rocks.

3. Marine bristle worms
Marine bristle worms (Polychaeta), particularly the fire worm, have tiny bristles that cause fierce skin irritation and inflammation.

Treatment:

  • Remove the bristles from the skin by sticking adhesive tape onto the affected area. Pull the tape off with a quick jerk.
  • Immerse the affected area in a bowl or basin filled with hot water for symptomatic relief.

How to prevent injury: Check where the nearest doctor or hospital is before you and your family spend the day at the sea.

Always be an alert swimmer and watch out for possible dangers. Wear protective clothing or a wetsuit when swimming.

Wear protective gloves when you're searching for sea delicacies, like mussels or abalone, among rocks.

4. Sponges



Sponges (Porifera) very commonly produce inflammation of the skin upon contact. Inflammation can last several weeks. A systemic reaction, in which other parts of the body are affected, hasn't been reported along the South African coastline.

Treatment: Treatment is symptomatic.

How to prevent injury: Check where the nearest doctor or hospital is before you and your family spend the day at the sea.

Always be an alert swimmer and watch out for possible dangers. Wear protective clothing or a wetsuit when swimming.

Wear protective gloves when you're searching for sea delicacies, like mussels or abalone, among rocks.

5. Molluscs
The only molluscs of real concern to South African beach lovers are sea snails. Bites from octopi and squids are rare in our waters.

Sea snails can inject a potent neurotoxin into the skin and should, therefore, be avoided.

Symptoms and signs of injury: Contact with a sea snail may result in inadequate flow of blood to the affected area. A burning pain and numbness may occur.

Respiratory failure, in which the person has difficulty breathing, may occur in serious cases, although this is rare.

Treatment: Treatment is symptomatic and supportive.

How to prevent injury: Check where the nearest doctor or hospital is before you and your family spend the day at the sea.

Always be an alert swimmer and watch out for possible dangers. Wear protective clothing or a wetsuit when swimming.

Wear protective gloves when you're searching for sea delicacies, like mussels or abalone, among rocks.

6. Stingrays, scorpion fish, toadfish, rabbit fish, stargazers and catfish



These fish have specialised devices, such as sharp spines or fins, through which they deliver their venoms.

Most of them are well-camouflaged, sedentary bottom dwellers. Injury usually occurs when one steps on them. Venom and even fragments of the spine are left in the wound.

Scorpion fish, and in particular the stonefish, are the most venomous in our waters.

Symptoms and signs of injury: In general, the venoms cause severe local pain and excessive accumulation of fluid in the affected area for several hours. Frequently, the wound bleeds heavily.

Local necrosis, in which some of the cells in the tissue die, is also common.

Systemic reactions – although rare – include nausea, abdominal pain, vomiting, excessive sweating, muscular weakness, seizures and even coma.

The wounds, notoriously slow in healing, often become infected.

Treatment:

  • Immediately rinse the affected area with copious amounts of seawater. Then immerse the area in a bowl or basin of hot water (45-50 degrees Celsius) for 30-90 minutes, or until the pain is relieved.
  • Seek medical attention if systemic symptoms or infection occur. Hospitalisation and/or treatment with antibiotics may be called for.
  • Your doctor may need to clean the wound by removing foreign material and dead tissue.

How to prevent injury: Check where the nearest doctor or hospital is before you and your family spend the day at the sea.

Always be an alert swimmer and watch out for possible dangers. Wear a pair of slipslops or flippers when swimming in the sea. Also stick to shallow waters and swim among other bathers. Fish have a tendency to stay away from places where people swim.

7. Sea snakes


The yellow-bellied pelagic sea snake is the only sea snake that reaches our shores. It is believed that its venom is 2-10 times more poisonous than cobra venom.

However, injury is uncommon. No actual cases have been documented locally.

Signs and symptoms of injury: The venom blocks neuromuscular transmission (the transmission of impulses from the nerve to the muscle) and may damage the kidneys.

Treatment:
 

  • Seek medical attention immediately. Hospitalisation, for at least 24 hours, to monitor and support respiratory and kidney function, is necessary.

How to prevent injury: Check where the nearest doctor or hospital is before you and your family spend the day at the sea.

Always be an alert swimmer and watch out for possible dangers. Also stick to shallow waters and swim among other bathers.

- (Carine Visagie, Health24, updated December 2008)

Read more:

12 extremely dangerous animals

Snake bites and poison

 

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