Researchers have found a new species of moray eel living in the murky river mouths of the Philippines, Japan, Taiwan, southern Java and Fiji.
The species – described in the journal ZooKeys – has been named after Hades, Greek god of the underworld, due to its striking, dark colouring and its preference for shadowy places.
Unlike most of its marine relatives, the mysterious Hades’ snake moray (Uropterygius hades) thrives in these freshwater habitats, making it a particularly exciting find.
A rare find
Around 230 species of moray eels are known worldwide – the majority of these are marine dwellers, with just one species confirmed to live primarily in freshwater.
Some marine species, such as the slender giant moray (Strophidon sathete), can tolerate brackish conditions and occasionally venture into river mouths.
However, morays specifically adapted to estuarine environments are exceedingly rare, making Hades’ snake moray an intriguing discovery.
The find came about by chance when researchers from National Sun Yat-sen University were exploring the Puerto Princesa Subterranean River in the Philippines.
They were hoping to locate the elusive bean-eyed snake moray (Uropterygius cyamommatus), known for its reduced eye size and adaptation to cave life. However, instead of their target species, they stumbled upon a different moray — a slender eel with a distinctive, uniformly dark appearance.
Hades’ snake moray: a closer examination
The researchers – including Dr Wen-Chien Huang from National Sun Yat-sen University in Taiwan, Dr Rodulf Anthony Balisco from Western Philippines University, and Dr Yusuke Hibino from the Kitakyushu Museum of Natural History and Human History in Japan – observed some fascinating behaviour in the Hades’ snake moray.
They found that it prefers to burrow tail-first, a rare trait among moray eels. It is also highly sensitive to light, consistently seeking out shelter when exposed to brightness.
Its small eyes and reduced number of head sensory pores suggest that it has adapted to navigate and hunt in low-light, sediment-heavy environments, relying more on chemoreception (responding to chemical stimuli, primarily using taste and smell) than vision to detect prey or evade predators.
Find out more about the study: Description of a new uniformly brown estuarine moray eel (Anguilliformes, Muraenidae) from the Central Indo-Pacific Ocean
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