Venomous creatures are an inseparable part of reef life. There is a constant, round the clock struggle for existence. In recent years we have witnessed a considerable decrease in the number and quantity of the various species of fish and invertebrates. In this struggle for existence the balance has been breached, and venomous creatures are not immune. Like dominoes that collapse one after the other in a chain reaction, marine life is also in danger of extinction and, once the process begins, it is very hard to stop it. It is enough for a single species of fish or invertebrate to disappear in order to affect the entire food chain; something which could have disastrous results on the entire ecosystem.
In nature, it is well known that the ability to defend yourself is a matter of life or death. Speed, strength, camouflage, deception and sophistication are some of the traits by which marine creatures survive. But creatures that are not equipped with these traits have been given venom.
There are about 1,000 marine creatures which are venomous. The topic of venomous creatures has always been filled with mystery, rumors, exaggeration and fantasy. Here we will try to put some order into this ancient subject. As long as 3600 years ago, the Egyptians tried to find antidotes against the venom of poisonous creatures, and also tried to describe a small portion of the creatures that are responsible for this damage.
As a child in Eilat, I remember the first time that I wanted to go into the water. My parents forced me to wear sandals. Of course I was very angry, but I was not yet familiar with the dangers that are lurking, awaiting ‘bare feet’.
Marine conus textile
With most venomous creatures, the venom is only a form of self-defense. The conus textile, a beautiful marine gastropod mollusk , is one of the exceptions to this rule; the conus textile uses its venom to paralyze its prey before eating it. The venom is located inside the venom gland which is connected by a harpoon-like tube which the gastropod shoots to its prey from its proboscis. The darts are produced inside a special sac and are stored at the front of the sac, ready for firing. The conus can shoot one dart each time, and simultaneously a new dart gets placed into the shooting position. Upon impact the end of the dart breaks and the venom inside it bubbles its way into the victim.
I’ll never forget the story about the poor fellow who wasn’t familiar with the venomous conus, and saw one for the first time. All he wanted was a nice memento from the Red Sea, and he collected the conus inside his swimming trunks. It is unnecessary to mention the pain and embarrassment on his face when he arrived at the ER and tried to explain the strange thing he had done.
Lionfish / Devil Firefish – Pterois miles
The Lionfish is a most beautiful predator and, as its second name indicates, certainly is a ‘firefish’. This is an active night predator with 13 very sharp spines on its back, with a venomous gland inside each spine. When pressing on the spine (swallowing by a predator, or touching by a human) the venom is released from the gland in the spine into the body of whatever has touched it.
The venom causes a sharp pain, often also swelling, but soaking in warm water dissolves the venom. When the firefish identifies danger it erects the spines in the direction of the danger and is ready for any possible confrontation. The firefish have beautiful and bright colors which can be seen from a distance, and it is these colors that also emphasize the spines, by which the firefish announces to everyone ‘I’m poisonous – you’re better off finding prey elsewhere’.
Striped eel catfish (Plotosus lineatus)
This is rare fish that lives in the southern part of the Gulf of Eilat – the venomous striped eel catfish, which reaches a size of up to 32 cm. When they are young, they live in schools of hundreds and as adults they live alone or in a school of a few dozen. The striped eel catfish has a venomous spine on the outside of each gill, and another venomous spine on the first dorsal fin.
The venom is located at the tip of the spine and results in terrible pain. In recent years a number of these fish have been found in the Mediterranean Sea.
Rabbitfish (Siganus rivulatus)
The rabbitfish – or, by it’s popular name, ‘venom’ – is a common fish, a vegetarian, and has a row of spines along its back which are covered in a venomous texture; when touched (often when attempting to throw a rod) the poison penetrates into the body of whatever has touched it.
Reef Stingray (Taeniura lymma) – Catfish
Catfish belong to the family of cartilaginous creatures and are very similar to sharks. At the base of its tail there are three venomous spines. Whenever it is in danger the catfish turns its tail so that the spines are visible and prominent.
These spines are particularly poisonous when they are touched and the tip of the poisonous spine is broken, so that the venom remains in the body of whatever touched them. Touching one can result in terrible pain, necrosis and inflammation due to the tip of the spine remaining inside the body. Catfish are shy and prefer to run from danger rather than use their venom.
Fire Coral – Millepora dichotoma
Fire Coral is part of the coelenterate system – marine stingers which are not true corals at all. These coral are found on the reef in shallow water and have stinging cells that they use to paralyze their prey. The name fire coral is justified in this case because, if touched, one feels a really strong sensation of being burned, and in extreme cases this can even result in the formation of blisters.
Upside down Jellyfish – Cassiopeia
Cassiopeia – ‘Upside Down’ jellyfish – live in shallow lagoons. They have stinging cells called nematocysts; when the Cassiopeia feels threatened it immediately releases these stinging cells into the water. The nematocysts are composed of capsules that are closed with a ‘door’; outside the door there is a spring clip that opens the door and pushes the spine through it, releasing poison into the threatening entity.
When this occurs, not all of the nematocysts open – in order to prevent those unopened cells from opening it is best to pour vinegar (antidote) onto the area.
The Sea Urchin – Asthenosoma varium
A venomous mechanism can also be found among the sea urchins. The poisonous glands of the sea urchin, which has a very intense color, has four different types of spine – the first, which is also the shortest, is used for protection: the venomous glands are located at the end of these spines and these are the only ones that contain venom. It is not the penetration by the spine which hurts, but the poison that is injected.
The second set of spines provides camouflage, and they are used as grasping rods with which the sea urchin can cover itself. The third set is used to help the sea urchin walk.
The last set of spines is used to help the sea urchin remain inside the crevices of the reef, which is where it hides during the day.
Orange Sun Coral – Sp. Dendrophyllia
This beautiful coral is probably the world’s most photographed coral and at a glance it is easy to understand why. The sun coral uses its stinging cells to protect itself, and also when paralyzing its prey. In contrast to reefs which need light in order to exist, the sun coral does not need light, and it must hunt for all its food. Its tentacles have clusters of stinging cells with which it hunts for its prey. Upon touch, the stinging cells burn and trap the food. During the night the sun coral spreads its tentacles and captures zooplankton to feed on.
Marine creatures that carry venom use it both for attack and for defense; there are a lot of them and their poisonous mechanism is both complex and interesting.
Sometimes fish / coral which appear to be innocent can cause a sensation of pain and burning. In order to avoid touching these and others, we should remember that we are visitors in the sea, and should not disturb their peace by trying to touch them.
Written by: Aviv Levi – The Scientific Director of the Underwater Observatory Park.