During a routine fishing trip near Costa Rica’s Tortuguero National Park, anglers reeled in a six-foot nurse shark unlike any other. Instead of the species’ typical muted brown tones, this shark’s eyes were stark white, and its body glowed bright orange.
Researchers later confirmed this creature carried two incredibly rare genetic conditions — xanthism and albinism — creating what scientists are calling albinoxanthrochromism. This phenomenon has only been documented once before, in a Homelyn ray caught in the Irish Sea in 1910.
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The shark, captured and quickly released at a depth of about 120 feet in August 2024, drew widespread scientific fascination. Lead researcher Marioxis Macias of Brazil’s Federal University of Rio Grande told Gizmodo that xanthism alone does not impair health. In this case, neither did the dual pigmentation anomaly.
Standing out in the deep
Nurse sharks are bottom-dwellers found throughout the Atlantic and Caribbean. They typically have brown, gray or yellowish coloring, which helps them blend into reefs as they feed on crustaceans and small fish.
This vibrant orange specimen defied that camouflage rule. Despite its striking visibility, the shark had reached adulthood, showing that its condition did not hinder survival in the wild.
A first for sharks
That said, the discovery has raised important questions: Did environmental pressures like inbreeding, ocean stress or hormonal shifts trigger this mutation? Is this a one-off fluke — or the start of a new genetic trend?
Once thought to be limited to certain fish, birds or reptiles, xanthism — especially in combination with albinism — had never before been recorded in cartilaginous fish, like sharks, in the Caribbean. The findings, recently published in the journal Marine Biodiversity, highlight the complexity of ocean genetics and adaptation.
