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  • Writer's pictureBeth Matlock

Small but deadly...

It's been a while since I have been active on here but now I have some spare time I am continuing with the series "Swim a mile in their seas". I will be showing you a specific species of marine organism that has extraordinary adaptations or behaviours that allow them to survive in such harsh environments.

Today's organism is the Glaucus atlanticus, otherwise known as the "blue sea dragon". The Glaucus atlanticus is a species of sea slug that is found in the open ocean and uses surface water tension to transport itself. This species is a nudibranch and part of the Glaucidae family. This particular species floats upside down on the top of the water, this is beneficial for it, the organism blends in with the colour of the water due to its body colour. It is able to do this due to a gas-filled sac in its stomach, the location of this sac means that it floats upside down. This adaptation works to deter both predators looking from the sky and also those looking from underneath the water. The underside of this species is silver grey and so blends in with the reflection coming from the sunlight on the surface of the water. So in essence, the Glaucus atlanticus hides in plain-sight ready to attack its prey, it is also thought that this particular colouration reflects UV sunlight.

These organisms are found in different parts of the world, namely the south coasts of South Africa and the east coast of Australia. Due to the passive movement of this species, they sometimes wash onshore during strong tides. This results in them being found in areas where they are not usually native such as areas in the Caribbean.

So what makes this species so dangerous?

Well, the primary prey of the Glaucus atlanticus is the Portuguese man o'war, which as many will know, is highly venomous. It is able to feed on these jellyfish due to its immunity to their venomous nematocysts (cells containing its sting). Another special adaptation of this species is its ability to store the venom from the Portuguese man o'war and use it in the future against prey. The venom is stored in the cnidosacs (feather-like 'fingers') on its body.

Now the term sea slug doesn't always sound like the most ominous creature, however, if you approached one you would soon regret it. Due to its ability to store venom from the prey it consumes picking up this species will result in a painful sting. Symptoms of this sting include erythema, vomiting, and post-inflammatory hyperpigmentation. So, in the future, when coming across this particular species do not pick it up. Like most sea creatures they are often better to admire from afar...

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