Skin lesions linked to sunburns (photolesions)

What is it?

Skin lesions linked to solar burns, also called photolesions, affect the manta ray (Mobula birostris) when its skin is exposed for too long and too close to the surface of the water, at times when ultraviolet radiation is most intense.\nThis phenomenon is mainly reported in mantas kept in shallow pools or observed on the surface for prolonged periods in their natural environment, particularly during surface swimming behavior (basking).\nThe skin of the dorsal side, more exposed, is the area most often affected.

We first observe a localized discoloration or blackening of the skin on the top of the body, especially on the disc and sometimes on the head.\nThe affected area may become thicker, rough or cracked, a bit like a scab.\nIn more severe cases, the skin may crack, revealing sores which do not heal easily and which remain fragile.\nThe animal may rub itself against the walls or bottom of the pelvis, try to change your swimming depth, or show less fluid swimming than usual.\nA general depression and a drop in interest in food may appear if the lesions are extensive or superinfected.

The main cause is excessive exposure of the skin to ultraviolet radiation from the sun, particularly when the animal remains for a long time at shallow depths or on the surface.\nThe skin of manta rays, although adapted to aquatic life, does not have the same natural protections as that of some other marine animals in the face of prolonged and repeated exposure.\nLesions occur more easily when the water is very clear and shallow, which allows more UV rays to pass through to the animal.

Commonly observed signs

These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.

References

WOAH — Organisation mondiale de la santé animale (ex-OIE)

Content reviewed by the TunisieVet editorial team · Updated 04 September 2026