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In A Nutshell
- A Narrow First: A 2025 Marine Biodiversity report called the orange nurse shark caught off Costa Rica in 2024 the first scientifically documented case of total xanthism in its species and the first from the Caribbean Sea, though brilliant yellow and milky-white nurse sharks had been reported before.
- Two Conditions, One Animal: Because the shark’s eyes looked white with no visible iris, researchers proposed it was most likely albino as well as xanthic, a conclusion drawn from photographs and the fishermen’s information rather than tissue or genetic tests.
- Big Questions Remain: The roughly 6.6-foot adult clearly survived to maturity, but one released animal cannot reveal what caused its color or how the condition affects its vision, feeding, reproduction or lifespan.
Nurse sharks spend their days resting on sandy bottoms and in rock crevices, colored anywhere from light tan to dark brown. The one that surfaced beside a sport-fishing boat off Costa Rica’s Caribbean coast in August 2024 was orange from snout to tail, and its eyes were white.
“We could not believe what we had in front of our eyes,” Garvin Watson, a hotel owner on the trip, told Live Science.
Within a year the shark had appeared in a scientific journal and in headlines calling it a first. The record holds up, but it is narrower than many of those headlines suggest, and it rests on a few photographs of an animal that swam away. Together with a review of abnormal fish coloring and an earlier report on an oddly colored nurse shark, the evidence shows what scientists can say about this animal and how much is still unknown.
What Did The Fishermen Actually Catch?
Not a new species, just a familiar one wearing the wrong color. According to Live Science, the fishermen photographed the shark, took out the hook and released it alive.
Research published in Marine Biodiversity on August 1, 2025 identified the animal as Ginglymostoma cirratum, the Atlantic nurse shark. The shark was caught near Tortuguero National Park, roughly 37 meters (121 feet) below the surface, and measured about 200 centimeters (6.6 feet) long. The research team, led by Marioxis Macías-Cuyare of Brazil’s Federal University of Rio Grande, never examined the shark in person. Their analysis relied on the fishermen’s photos, measurements and account.
How Narrow Is The ‘First’ Claim?
Very narrow, and that matters. Adult nurse sharks generally range from light tan to dark brown, according to the Florida Museum of Natural History. The museum also notes that unusually colored individuals, including brilliant yellow and milky-white ones, have been reported several times.
A 2023 review in Cybium gathered published reports of xanthochromism, an abnormal yellow-to-orange coloring, in 68 wild marine fish species. Seven were cartilaginous fishes, the group that includes sharks and rays, and the nurse shark was among them. The authors cautioned that similar natural colors can be hard to separate from abnormal ones, and that some species on their list may have been misidentified.
The Costa Rican record claims something more specific: the first scientifically documented case of total xanthism in the species, with orange covering the whole body, and the first such record from the Caribbean Sea.
Why Do The White Eyes Matter?
They may point to two pigment conditions at once. Xanthism brings out yellow and orange tones. Albinism involves a lack of dark pigment, which can affect eye color. Shark eyes typically have black irises, and this one appeared to have none. The researchers wrote that the shark was “most likely” displaying albino-xanthochromism, an overlap of the two conditions, rather than xanthism alone.
Live Science noted that a 2018 study had documented the combined condition in a ray from the Irish Sea. Co-author Daniel Arauz told NPR that the team had never seen it in a shark.
Reports on the study describe no tissue sampling or genetic testing. That means the albinism, in particular, is a reading of how the eyes looked in photos, not a lab result. The paper says xanthism is usually genetic, but that inbreeding, environmental stress, elevated temperatures and hormonal imbalances may also play a role, and it calls for more research into local conditions. Macías-Cuyare told Live Science that everything “remains speculative” until those factors are tested.
Nurse sharks hunt at night and spend daylight hours resting on sandy bottoms or in caves and rock crevices, according to the Florida Museum. The study’s authors wrote that their finding suggests xanthism does not hinder survival in this species. Nick Whitney, a New England Aquarium scientist who was not involved in the research, told NPR that the color may have made the shark more conspicuous when it was young but that it appeared to be a healthy adult. Whether the condition affects its eyesight, feeding, reproduction or lifespan is still unknown.
What Does The Evidence Actually Support?
A rare, well-photographed record, not a full biological explanation. A 2022 Journal of Fish Biology report on the first documented piebald nurse shark, spotted by divers off Honduras, likewise pointed out how little is known about how pigment disorders affect survival in sharks and their relatives.
For a few minutes beside a fishing boat, a shark species usually muted against the seafloor became impossible to overlook. Because the fishermen released it, the Caribbean kept nearly every answer its orange skin brought to the surface.
