The Hades’ snake moray (Uropterygius hades), a dark brown, slender snake moray eel, has chosen the road less traveled, thriving in dim and muddy river mouths, unlike most of its marine moray eel relatives. It is widely distributed across the Central Indo-Pacific, and has been found in southern Japan, Taiwan, the Philippines, southern Java, and Fiji. This new moray eel was named after Hades, the god of the underworld, due to its unique habitat, burrowing behavior, high sensitivity to light, and most notably, its deep, dark coloration.

Scientists Dr Wen-Chien Huang, Dr Rodulf Anthony Balisco, Dr Te-Yu Liao, National Sun Yat-sen University, Taiwan, Western Philippines University, the Philippines, and Dr Yusuke Hibino, Kitakyushu Museum of Natural History and Human History, Japan, describe this new species in a paper published in the open-access journal ZooKeys. They named it after Hades, the underworld god, to emphasize its imposing appearance and its habitat in dim, turbid environments. This idea was inspired by Dr. Wen-Chien Huang, who was influenced by Ralph Fiennes' portrayal of Hades in the movie Clash of the Titans.

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.

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.

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.

Original source:

Huang W-C, Hibino Y, Balisco RA, Liao T-Y (2024) Description of a new uniformly brown estuarine moray eel (Anguilliformes, Muraenidae) from the Central Indo-Pacific Ocean. In: Ho H-C, Russell B, Hibino Y, Lee M-Y (Eds) Biodiversity and taxonomy of fishes in Taiwan and adjacent waters. ZooKeys 1220: 15-34. https://doi.org/10.3897/zookeys.1220.129685