Stonefish: Venomous touch

Another ambush predator is the infamous stonefish because of its venomous touch. The venom of the stonefish is the strongest not only of all the ambush predators, but of all fish, and a sting, depending on the amount of venom entering the victim, can be fatal also for humans.

Estuary stonefish (Synanceia horrida) with a bony ridge above and between eyes, while the eyes of the reef stonefish are further apart with a deep pit in between.

Ambush predators: Estuary versus reef stonefish

The face of horror (Synanceia horrida) in the picture above shows the distinguishing feature between the estuary and the reef stonefish: The bony ridge above and between the eyes. On the contrary, the eyes of the reef stonefish are far apart with a deep pit in between. Estuary stonefish can grow up to 60 cm and are usually of a dull brownish to reddish colour, perfect to camouflage among rocks and sandy bottoms. In addition, some individuals even have real algae growing on them to add the final touch to their camouflage.

Their home base

Synanceia horrida can be found in coastal areas of the Indo-Pacific from India to China and down to the Philippines and Papua New Guinea to Australia and everywhere in between. Their main habitat is close to or on coral reefs and in estuaries, in salt or brackish water.

Waiting for their food to deliver itself

Then they lie and wait for unsuspecting prey, mostly small fish, to come close. When the victim is less than their body lengths away, stonefish quickly open their mouth and suck the fish as a whole into their huge stomach. In the same way, stonefish swallow shrimps and other crustaceans, the same powerful sucking motion their fellow ambush predators use (Ambush predators: They got the look).

Underwater close-up of estuary stonefish (Synanceia horrida) showing the dark pupils in focus as well as the huge mouth facing down. Algae and sand are perfecting its camouflage. Colour light to darker brown with yellow, orange and red. Picture taken in Amed, Bali, March 2020. Stonefish: Venomous touch. — Estuary stonefish (*Synanceia horrida*): The eye helps to distinguish stonefish from another ambush predator devil scorpionfish.

Venomous touch as defence

Like all the other venomous ambush predators, stonefish don’t use their venom to hunt or use it in an aggressive manner. Instead, the venom is their guarantee against other predators as well as people not paying any attention to where they are placing their hands, feet or knees. That’s the stonefish’s venomous touch. The stronger the pressure at that point and the bigger the area that is in contact with the stonefish, the more venom can enter the bloodstream of the involuntary attacker. Nevertheless, humans still catch stonefish – on the one hand for the aquarium trade and on the other, they are a delicacy in some countries as their meat is not poisonous.

Venomous versus poisonous

Poisons are working through touch, ingestion or inhalation while a venom has to be injected directly into a wound, via venomous spines in the case of the estuary stonefish.

“According to biologists, the term venomous is applied to organisms that bite (or sting) to inject their toxins, whereas the term poisonous applies to organisms that unload toxins when you eat them.”
Britannica: What’s the differencebetween venomous and poisnous

Pufferfish are poisonous, producing a deadly neurotoxin (tetrodotoxin more toxic than cyanide) for their skin and organs out of a marine bacterium. However, that’s not keeping all humans from eating them.