Camouflage or Warning Coloration?

Another Lens on Life post by Chuck Kopczak, PhD

10/19/2020
A yellow, brown and white rocky-looking blob sits in the water among other brightly colored sea creatures. Oh wait, the blob is a fish!
Chuck Kopczak, PhD

A yellow variant of the leaf scorpionfish (Taenianotus triacanthus) on Rainbow Reef, Vanua Levu, Fiji

Today's photo was taken on a segment of Rainbow Reef known as Rainbow’s End off the South East coast of Vanua Levu, the second largest island in the Fiji archipelago. It was made with a Canon 100 mm f/2.8L lens mounted on a Canon 5D Mk. III in an Ikelite underwater housing. It was illuminated by two Ikelite DS-161 strobes set on eTTL. The exposure was set to 1/60 sec at f/11 and ISO 200.

The leaf scorpionfish (Taenianotus triacanthus) is a small member of the scorpionfish family, typically reaching lengths of no more than four inches (10 cm). And while they do possess the venom-injecting spines characteristic of scorpionfish, their venom is much weaker than that of the lionfish and stonefish, the more well-known members of the group.

Like most scorpionfish, the leaf scorpionfish is an ambush predator and has evolved several camouflage strategies. Their common name suggests the first strategy, which is to sway gently in the current, or even in the absence of water motion, to simulate the drifting motion of a leaf or other piece of debris. This combined with disruptive coloration disguises the outline of the animal, making it possible for them to hide in plain sight.

Leaf scorpionfish come in a range of colors including red, brown, white, green and yellow. When viewing the yellow color variant, even with its disruptive coloration, one wonders whether the hue is meant to camouflage the animal or serve as a warning to potential predators. While a yellow leaf scorpionfish sitting on bright yellow sponge would be virtually invisible, sitting on almost any other background it would seem to stand out like a warning flag. It may be, and this is pure speculation on my part, that the yellow leaf scorpionfish is combining strategies to veil itself from prey, while simultaneously warning potential predators of its venomous nature. The leaf-like behavior and disruptive coloration may conceal it from potential prey, while its bright color may advertise to potential predators that it is not to be bothered. This could be an interesting project for a graduate student to figure out someday.

Sources

https://fishesofaustralia.net.au/home/species/3342

https://australian.museum/learn/animals/fishes/leaf-scorpionfish-taenianotus-triacanthus/

https://www.discoverlife.org/20/q?search=Taenianotus+triacanthus