In 2024, sport fishers off Costa Rica's eastern coast captured a unique 6.6‑foot nurse shark (Ginglymostoma cirratum) with bright orange skin and stark white eyes. The specimen was released back into the wild after the catch.
Because the shark was still alive, scientists could not perform a direct examination, but photographic evidence and subsequent analysis suggest that the unusual coloration results from two rare genetic conditions: xanthochromism— a yellowish hue caused by a lack of darker pigments—and albinism, which reduces melanin production and often results in white hair, skin, and eyes.
Xanthochromism is exceptionally uncommon in marine life. This nurse shark represents the first documented case of complete xanthism in its species, and the first cartilaginous fish in the Caribbean to exhibit the trait. Similar occurrences have been recorded in 2021 among fish in the Arabian Sea and in 2024 with the common snook (sergeant fish). Birds and other taxa have displayed the condition, but a nurse shark with this pigment profile is unprecedented.
White eyes, a hallmark of albinism, further support the hypothesis that the specimen was albino. While albinism is more frequently observed in fish, the simultaneous presence of xanthochromism and albinism produced a strikingly distinctive appearance.
Research published in the journal Marine Biodiversity notes that the shark was fully grown, implying that its coloration likely did not compromise its survival. Nurse sharks typically display a yellow‑brown to dark brown palette, but pigmentation is integral to camouflage and mate selection. The rarity of this combination suggests that, if other similar individuals exist, they could be viable subjects for future study.
Although xanthochromism is thought to be genetic, the authors point out that environmental stressors—such as elevated temperatures—could have contributed. Inbreeding and hormonal imbalances are also potential explanations. Further investigation is needed to determine the exact mechanisms behind this extraordinary pigmentation.
