This species is frequently confused with C. argus but can be distinguished by the following characters: dorsal-fin rays 38-45 (vs. 47-50 in C. argus); anal fin rays 26-29 (vs. 31-36); lateral line scales 50-56 (vs. 60-66); 2-3 rounded blotches on caudal peduncle (vs. no blotches on caudal peduncle).

It is widely-distributed in Pacific coastal drainages of southeastern China (e.g. the Yangtze, Minjiang, Hangjiang River, and Pearl (Nanjiu…

P. arnoulti has been in the aquarium hobby for many years but was identified as the congener P. omalonotus prior to its description.

It appears in the majority of older aquarium literature under that name and as a result a degree of hybridisation has undoubtedly occurred.

Butis spp. are largely nocturnal ambush predators with cryptic patterning to help them blend in with their surroundings. They can also lighten and darken their body colouration to an extent, have a habit of aligning themselves with solid surfaces whether horizontal, vertical, or inverted, and often swim in an upside-down position.

The genus is usually included in the family Eleotridae of which members are often referred to…

This species was first imported for the aquarium hobby during the 1950s and was for many years misidentified and traded as Bedotia geayi, a valid, but different-looking congener native to the Mananjary River system, south of the range of B. madagascarensis. In terms of external characters, the two are most easily told apart by differences in colour pattern, particularly that of the unpaired fins, and some morphometric counts.

The majority of original populations have already been extirpated due to introduction of invasive species such as Gambusia holbrooki and Poecilia reticulata, ongoing deforestation of the Ambohitra Massif, and physical diversion of the source of the Sakaramy River for domestic use by locals.

An additional population may exist in a stream on the southern slope of the Ambohitra Massif on the road between Bobasokoa and Anivorano, near the village of Andranotohiliny, but this requires verification.

Wild swordtails are a fairly basic green colur. However the vast majority of swordtails available in the hobby today are hybrids of X.helleri with X.maculatus or X.variatus. There are a huge number of selectively-bred varieties available, including wagtail, lyretail, tuxedo, albino, neon, red, green and hi-fin.

Swordtails may undergo what appears to be a change in sex. In young fish this may simply be late development. However some adult females develop male characteristics which is thought …