The Hades’ snake moray, a unique species found in dim, muddy river mouths, has been discovered and named for its underworld-like qualities, including its dark coloration and burrowing behavior.
Originating from the Central Indo-Pacific, this species stands out for its adaptability to low-light and turbid environments, sparking intrigue among scientists who stumbled upon it while seeking another eel species.
Discovery and Naming of a Unique Moray Eel
The Hades’ snake moray (Uropterygius hades) is a slender, dark brown eel that thrives in the dim, muddy waters of river mouths — an unusual choice compared to its mostly marine moray eel relatives. Found across the Central Indo-Pacific, this species has been recorded in locations such as southern Japan, Taiwan, the Philippines, southern Java, and Fiji. Its name, inspired by Hades, the Greek god of the underworld, reflects its unique habitat, burrowing behavior, sensitivity to light, and striking deep-dark coloration.
Scientists Dr. Wen-Chien Huang, Dr. Rodulf Anthony Balisco, Dr. Te-Yu Liao, and Dr. Yusuke Hibino, affiliated with institutions in Taiwan, the Philippines, and Japan, detailed this new species in the open-access journal ZooKeys. The name Hades underscores the eel’s dramatic appearance and preference for shadowy, turbid environments. The inspiration for the name came from Dr. Huang, influenced by Ralph Fiennes’ portrayal of Hades in the movie Clash of the Titans.
Rarity of Estuarine Moray Eels
There are approximately 230 species of moray eels worldwide, with most inhabiting marine environments. Only one species has been confirmed to spend the majority of its life in freshwater. Some marine species, like the slender giant moray (Strophidon sathete), can tolerate and occasionally enter lower-salinity environments such as river mouths. However, moray eels specifically adapted to estuarine habitats are exceedingly rare.
Accidental Discovery and Adaptations
The discovery of Hades’ snake moray was actually accidental, when the three researchers from National Sun Yat-sen University investigated the cave of the Puerto Princesa Subterranean River, aiming to survey the aquatic fauna and targeting a cave eel species, the bean-eyed snake moray (Uropterygius cyamommatus). This eel, with its highly reduced eye size, is considered an ideal example for studying the evolutionary processes that allow eels to adapt to cave environments. However, the researchers did not find any bean-eyed snake morays in the cave; instead, they collected a slender moray with a conspicuous, uniformly deep dark color.
Burrowing Behavior and Sensitivity to Light
When kept in an aquatic tank, the Hades’ snake moray exhibits tail-first burrowing behavior, which is rarely seen in moray eels. Additionally, it is highly sensitive to light, consistently attempting to hide when exposed to it. Its small eyes—thought to be an adaptation to low-light environments—and its reduced number of head sensory pores—believed to help avoid clogging by the substrate—suggest that this species might be an excellent burrower, relying primarily on chemoreception rather than vision to detect prey or avoid predators.
Reference: “Description of a new uniformly brown estuarine moray eel (Anguilliformes, Muraenidae) from the Central Indo-Pacific Ocean” by Wen-Chien Huang, Yusuke Hibino, Rodulf Anthony Balisco and Te-Yu Liao, 9 December 2024, ZooKeys.
DOI: 10.3897/zookeys.1220.129685
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