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Marine biologists say they have discovered a rare, bright-orange skin nurse shark off Costa Rica\u2019s Caribbean coast. Credit: Jaimedelamata<\/a> \u2013 CC BY-SA 3.0 via Wikimedia Commons.<\/p>\n Marine biologists say they have discovered a rare, bright-orange nurse shark off Costa Rica\u2019s Caribbean coast, the first recorded case of xanthochromism (also xanthism) in cartilaginous fish species in the region. According to the scientists, the finding raises new questions about shark genetics and survival.<\/p>\n The roughly 2-meter (about 6.6-foot) shark was captured during a sport-fishing trip near Tortuguero National Park\u2014located in the northeastern part of the country in Lim\u00f3n Province\u2014at a depth of about 37 meters (121 feet) in August 2024, when it was photographed and then released, researchers reported.<\/p>\n The particular nurse shark\u2019s vividly orange skin and unusual white eyes, which scientists have described as having \u201cno visible irises,\u201d prompted scientists to identify the condition as xanthism, a genetic pigmentation anomaly that results in excess yellow or golden tones. According to the team, the eyes point to a rare case of albino-xanthochromism rather than xanthism alone.<\/p>\n Rare bright-orange nurse shark caught in Costa Rica marks first-ever Caribbean case of xanthism.<\/p>\n Follow: @AFpost<\/a> pic.twitter.com\/GuHxX2X0nN<\/a><\/p>\n \u2014 AF Post (@AFpost) August 19, 2025<\/a><\/p>\n Xanthism causes the condition in the bright-orange nurse shark<\/p>\n The discovery of the particular fish off Costa Rica, detailed in a paper by scientists at the Federal University of Rio Grande and published in the journal Marine Biodiversity, is notable because this species is typically brown, a coloration that helps it blend into the seabed. This means that the bright-orange nurse shark prominently stands out from others of its own species.<\/p>\n \u201cGiven how infrequently xanthism is observed across animals, the Costa Rica case adds a rare data point from a region where the condition had not been recorded,\u201d the authors wrote, noting that the finding expands understanding of pigment variation in Caribbean<\/a> shark populations.<\/p>\n Xanthism has been documented in only a handful of animals worldwide. The condition produces yellow morphs in some fish and birds and is thought to be primarily genetic.<\/a> Environmental factors such as inbreeding, stress, elevated temperatures, hormonal imbalances, or diet might influence pigmentation as well, revealed the researchers.<\/p>\n The shark\u2019s pigmentation makes it more vulnerable to predators<\/p>\n Bright coloration and white eyes associated with albinism, as in the case of the bright-orange nurse shark, can make animals more visible to predators, leading scientists to expect lower survival rates for such individuals. In this case, the size of the fish suggests it had reached adulthood, and \u201cit appears that this unusual pigmentation did not affect its survival,\u201d the authors said.<\/p>\n The team urged additional monitoring and genetic study of the bright-orange nurse shark to determine how widespread pigmentation anomalies may be among Caribbean<\/a> sharks in general and whether regional environmental pressures contribute to these.<\/p>\n The discovery, documented in high-quality images and footage from the sport-fishing trip, provides a rare glimpse into the genetic diversity of marine life in Costa Rican waters and may prompt researchers to look more closely for traits similar to that of the nurse shark in cartilaginous fish across the region.<\/p>\n