A holiday at the seaside must surely rate high on most people’s list of things to do. We certainly crave the annual trip to the coast. Fossicking around in the rock-pools, doing a bit of fishing perhaps, swimming or snorkelling in the warm waters of the Indian Ocean, or simply soaking up the sun all do it for us…
Life can be pretty good on such a holiday. There are a few things that we would like to tell you about, however. Amongst the wonders and the beauty of ocean life there are a few creatures to take note of for the simple reason that to have an encounter with one could spoil your day – if not your holiday. We offer this not to scare you off but rather so that you can look at these creatures in safety and without inadvertently being stung or bitten. Sounds awful, doesn’t it!
The first on our list is the ubiquitous blue-bottle – also known as the Portuguese Man o’ War – which is found in the surf when the wind sometimes blows them inshore. This creature is fascinating in that it is not one animal but is made up a community of creatures each with a different function. The most visible part is the sail – the blueish bubble that keeps the creature afloat, and which enables the wind to move vast numbers of these creatures across the surface. Beneath this lies a seemingly random entanglement of blue tissue that actually is the digestive and reproductive systems, and then, dangling below all this, is the business end – the sting. This is a long filament of elastic tissue liberally coated with stinging cells. Under a microscope one can see that each cell has a minute harpoon and a hollow line in it. When anything brushes against the stinging cells it triggers a mechanism that enables the cell – or many cells – to burst and “fire” the harpoon and line into whatever caused the disturbance, administering a venom on penetration. In this way the blue-bottle is able to harpoon small fish or other marine creatures. The venom kills or stuns the victim and the creature then draws the victim up to the digestive system where it is consumed. Large creatures like big fish or even humans simply get stung and retire from the scene very smartly!
Our local blue-bottles are anything up to about 6 cm long, although much larger specimens are found in other parts of the world with sting filaments over 20 metres long. An interesting phenomenon is that the common beach snails that ones sees in the wash zone, make a beeline for stranded blue-bottles and avidly consume them!
So, what to do when there are blue-bottles around? Prevention is always better than cure, so if you spot blue-bottles in the water it’s best to get out and swim another day.
Remember that a big local blue-bottle can have a sting over a metre long, so it’s best not to take chances. Even those “dead” ones that are washed up on the beach still have active stinging cells – so treat them with caution. One can hold the bubble safely, as the stinging cells only coat the tail. It can be quite fascinating to watch a blue-bottle in a glass tank to see just how much they move.
And what to do if you get stung? Firstly, if you have a blue-bottle tail wound around your ankle or arm, resist the temptation to pull it off. This movement only causes a lot more stinging cells to fire their weapons into your skin and worsens the discomfort. Rather try to lift the filament up and remove it that way.
The current suggestion is to soak the stung part in hot water of about 43degrees C . The heat will denature the venom and ease the discomfort. There is debate about the efficacy of applying a weak acid such as vinegar, which was the old-fashioned cure.
The venom should not have any serious effects, unless the person stung is allergic to it. In that case get medical help as fast as you can. Men who have received a good dose of the venom around the ankle or leg have reported feeling the pain moving up the leg to the groin. Then the pain can become pretty acute. So please don’t take blue-bottle stings lightly. Treat them promptly – and treat the victim kindly. It’s nothing to laugh about!
For more on the blue-bottle go to: http://animals.nationalgeographic.com/animals/invertebrates/portuguese-man-of-war/
You may also look on Google for: blue-bottle Physalia South Africa.
Next moth we’ll discuss another marine beastie that could spoil your day – or could provide hours of entertainment if you watch it carefully.