According to a new study, fishing guide Garvin Watson found an unusual shark near Tortuguero National Park in the Caribbean Sea at a depth of 37 meters. He caught and then released a nearly two-meter-long shark with white eyes and bright orange coloring.
“It was hard to believe what I was seeing. This orange shark, shimmering in the sunlight, was something extraordinary,” Watson told Live Science.
The creature, the species Ginglymostoma cirratum—commonly known as the nurse shark—was diagnosed by oceanographic biologists at the Federal University of Rio Grande in Brazil with xanthochromism. This rare condition is characterized by an increase in yellow or golden pigmentation of the skin. The shark also showed signs of albinism.
What Did the Scientists Report?
The research team had previously encountered xanthochromism, but this is the first documented case of pronounced yellow-orange coloration in a nurse shark.
Researchers spoke with Watson and examined photographs of the nurse shark. They noted that the shark lacked the typical black irises and concluded that it was likely an albino. The presence of albinism makes it even more extraordinary.
A previous study in 2018 documented this combined condition, known as albinism-xanthochromism, in rays of the species Raja montagui found in the Irish Sea.
The Brazilian research team, which continues to study the phenomenon of the yellow-orange nurse shark, attributes its abnormal pigmentation primarily to genetics. But other factors could contribute: a stressful environment, rising ocean temperatures, and hormonal imbalances.
Lead author of the study, Mariokis Masiás-Cuyare, a doctoral student in biological oceanography, noted that xanthochromism most often arises from genetic causes. But the team says further research is needed to determine what else influences the shark’s pigmentation.
The scientists were astonished that the nurse shark had survived to adulthood with such coloring. Typically, animals evolve to acquire certain colors that help them blend in with their environment. Therefore, the bright orange color, which is not characteristic of this species, could pose a survival challenge for the shark. Fortunately, that didn’t happen.
The researchers published their findings in the journal Marine Biodiversity.
