FishCommonVisible while snorkeling

Red Sea mimic blenny

Ecsenius gravieri

The reef's finest actor: this harmless little Red Sea endemic impersonates a venomous fangblenny so perfectly that predators give it a wide berth.

Photo: iNaturalist – (c) Georgina Jones, some rights reserved (CC BY-SA), uploaded by Georgina Jones

The Red Sea mimic blenny (Ecsenius gravieri) is a tiny fish of just 6–8 centimetres, pale blue in front, shading into bright yellow towards the tail, with a black stripe running back from the eye. It lives only in the Red Sea and the Gulf of Aden – so at Hurghada you are watching a true endemic speciality you would search for in vain in any other sea.

This species is one of biology's most famous textbook examples of Batesian mimicry: it copies, down to the last detail, the venomous blackline fangblenny (Meiacanthus nigrolineatus), whose bite injects a painful venom cocktail into an attacker's mouth. Predators have learned to avoid that experience – and the mimic enjoys the protection for free, despite having neither fangs nor venom. The resemblance is so strong that even divers regularly confuse the two.

It is common on Hurghada's shallow reefs, perching on coral heads and rock surfaces or swimming off in short bursts with a characteristic undulating motion – unlike its bottom-crawling relatives, because its model swims in open water too. You can easily watch it while snorkeling if you scan the corals slowly at one or two metres. The real connoisseur's challenge: working out whether you are looking at the original or the copy.

Did you know?

The mimicry is so location-bound that the mimic blenny lives only where its venomous model does: outside the Red Sea the costume would be worthless, because local predators would never have learned to fear the original.

Where can you meet it?

It occurs on nearly every shallow Hurghada reef: you will regularly spot it on the reef top of El Fanadir, the coral patches of Shaab Sabina and in the lagoons of the Giftun Islands.

Frequently asked questions

No – that is exactly the joke: Ecsenius gravieri is completely harmless and merely wears the costume of the venomous blackline fangblenny (Meiacanthus nigrolineatus). Even the model's bite is no real danger to humans, just a stinging memory – though of course you should not handle either of them.

With difficulty – that is the whole point. The best clue is the dorsal fin: the mimic's is notched at the front, while the venomous original's runs smooth, and the original hovers more boldly in open water. Take a photo and do the detective work back on the boat.

Yes, it is endemic to the Red Sea and the Gulf of Aden – just like its model. This famous mimicry duo can therefore be watched live nowhere else on Earth but here, for instance on Hurghada's reefs.