Cyclocheilos enoplos

Cyclocheilos: from the Ancient Greek κύκλος (kýklos), meaning 'circle', and χείλος (cheílos), meaning 'lip'.

enoplos: from the Ancient Greek ένοπλος (énoplos), meaning 'armed', in reference to the osseous, serrated dorsal-fin spine.

Currently understood to have an enormous natural range extending southwestwards from the Mekong region in Laos, Cambodia, and Vietnam through Thailand, and into Peninsular Malaysia and the Greater Sunda Islands of Borneo, Sumatra, and Java.

It thus occurs throughout the Mekong, Mae Klong and Chao Phraya river drainages as well as a host of smaller river basins, lakes and reservoirs. It is used as a food fish in some countries and may vary a little in colouration and patterning depending on collection locality.

Type locality is 'Kalimas River, Surabaya, Java, Indonesia'.

A riverine species exhibiting mid-water to benthic foraging behaviour during the dry season, and is thought to migrate to flooded riparian forests during the wet season in order to reproduce.

In the Mekong, it has been observed to migrate upstream from Phnom Penh to Khone Falls between November and February, returning downstream between May and August. The downstream migration ends in the Mekong delta area in Vietnam, where the fish remain until the floods reach their peak in October and November. These lower Mekong migrations mostly comprise juveniles and sub-adults, whereas above Khone Falls, upstream migrations between April and September are dominated by adult fishes and appear to represent spawning migrations.

Suitable only for outdoor ponds, public installations or the very largest, highly-specialised private aquaria.

A large, mature filter system, rigorous maintenance regime comprising weekly water changes of 50-70% tank volume should be considered mandatory, but décor is likely to be relatively unimportant.

Young fish can be offered chironomid larvae (bloodworm), small earthworms, chopped prawn and suchlike while adults should accept larger items as well as dried pellets, although the latter should not form the staple diet.

Relatively peaceful with fishes too large to be considered prey.

Sexually mature females are likely to be thicker-bodied than males.

See 'Habitat' for some basic information.

C. enoplos is clearly an unsuitable aquarium subject, and it is scarce to non-existent in the ornamental trade.

Cyclocheilos species have been included in the genus Cyclocheilichthys in the past, but can be separated by their larger adult size (typically 600 mm24 in+), more elongate body shape, possession of a large and long dorsal-fin spine, and ramified lateral line tubes.

There have been some nomenclatural issues in recent years, ostensibly because Cyclocheilichthys and the now synonymous Anematichthys were used simultaneously by Bleeker (1859) in reference to the same fish, C. apogon. The issue was addressed by Kottelat (1999) but later misinterpreted by Pasco-Viel, Veran and Variot, 2012, who concluded that Cyclocheilichthys represents a paraphyletic grouping and split the genus into two groups: Cyclocheilichthys (comprising C. enoplos) and Anematichthys (comprising C. apogon, C. armatus and C. repasson).

This was corrected by Kottelat (2013), and Cyclocheilichthys currently comprises seven species with the revalidated genus Cyclocheilos including the former members C. enoplos and C. furcatus.

Given the extremely wide range exhibited by C. enoplos, and taking into account patterns observed in other Southeast Asian fishes, it seems logical that this species may also turn out to represent a group of closely-related taxa.