For the first time, a group of scientists documented a shark with xanthism, a genetic condition that causes the animal’s skin to be devoid of dark pigments and, instead, display an orange coloration.
This is a shark of the species Ginglymostoma cirratum, which had been captured during sport fishing off Tortuguero National Park, in Costa Rica, at a depth of 37 meters. In an article published in the journal ‘Marine Biodiversity’, the scientists say that this adult individual, measuring about two meters in length, is the first scientifically documented case of total xanthism in the species and the first recorded in the Caribbean Sea.
Furthermore, they also say that “this unique discovery suggests that xanthism does not impact survival in this species”.
The research team was first alerted to the unprecedented case through photographs they received from the fishermen who had captured the shark. Marioxis Macías-Cuyare, from the Federal University of Rio Grande (Brazil) and the first author of the article, recalls, quoted in a press release, that “it was quite impactful to see the photos, because we were facing something unprecedented, a case of xanthism in this species, so we researched and wrote as quickly as possible to publish”.
“And the news has impact, because it is the first time that such a report has been made,” she adds.
In addition to the orange skin, the shark also had white eyes, so the scientists believe it to be a condition called albino-xanthochromia.
“This anomaly had already been reported in frogs and in many other terrestrial vertebrates,” says Macías-Cuyare, “but it had never been reported for sharks,” although there are, albeit very rare, reports of the condition in teleost fish, such as the grouper.
The team does not yet know whether this orange shark is an isolated case or whether it may belong to a population of Ginglymostoma cirratum sharks that share the same genetic condition, passed from generation to generation.
After being documented, the animal was released back into the sea, and the scientists say that more research is needed to understand which factors, genetic or environmental, influence these pigmentation anomalies in sharks.
