The crossed fork back golden-line fish – Sinocyclocheilus furcodorsalis

Sinocyclocheilus furcodorsalis

Sinocyclocheilus furcodorsalis

Rarely seen blind, humpbacked cave dweller

To discover this curiosity, we go underground and present one species of one the most extraordinary ecosystems in the world: the caves and karst systems of southern China. While extensive karst systems are well known from southern Europe, Mexico, Indochina and the USA, China has the most diverse underground fauna, at least when it comes to fishes.

In China, 92 described species of hypogean (cave and artesian) fishes are documented until now. In China, nearly one third of all the described hypogean fish species (299) are found, more than any other country. Of all Chinese hypogean fishes 56 species show troglomorphisms, i.e., adaptations that have been correlated to the hypogean environment such as reduction and/or loss of eyes, pigmentation, and the gas bladder.

Two other characters seem to be unique to some Chinese hypogean species: presence of a horn-like structure and hyperdevelopment of the dorsal protuberance similar to a humpback. This is also seen in our species of the month. The function of the unique dorsal protuberance in Sinocyclocheilus is unknown. This structure is only present in some hypogean species and absent in epigean Sinocyclocheilus. Despite the fact that the first written account of a cave fish was for species found in China in 1540, almost all the new descriptions have taken place in the last 20 years mostly in papers written in Chinese and in journals of difficult access outside China.

Our species of the month was described in 1997 and there is nothing more known on the species that how it looks like. There is almost no knowledge on the biology of the hypogean fishes of China and only few have larger distribution areas. Sinocyclocheilus furcodorsalis was described from an underground river at Tian’e County in Guangxi Province and seems to be restricted to this area. Several species are highly threatened by extinction due to mining and touristic development of their habitats and some might have been seen only once taken out of the darkness and then never again. This especially tragic, as highly adapted hypogean fishes as Sinocyclocheilus are very interesting to study the evolution and adaptation of animals to the underground environment.

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