This species has been traded for a number of years, though not always under the correct name. We've seen it on sale as S. elegans or S. atropurpureus on numerous occasions, for example, and other trade names include 'Sumatran blue neon goby', 'cobalt blue goby' and 'freshwater neon goby'. Further confusion has arisen because other species are sometimes sold as S. semoni meaning identification has not always been easy and there …

There also exists a sister-group relationship between the Melanotaeniidae and Malagasy family Bedotiidae, which may seem surprising given their respective modern-day distributional patterns. The precise origin and subsequent dispersal of the two families has been the subject of debate, with some palentologists suggesting that Madagascar’s freshwater fishes derived froma trans-oceanic dispersal during the Cenozoic Era, but the most compelling arguments currently indicate a freshwater radiation which occurred during the Mezozoic break-up of Gondwana.

Occurs in northern and eastern Australia and southern New Guinea.

In the former its range extends from the Pilbara and Kimberley regions of Western Australia state around the northern and eastern coastlines of the continent as far as the Towamba river system in New South Wales state.

Described from ‘Rivulet in sago forest at Ngaiguli, Terangan, Aru Island, Aru Islands, Maluku, Indonesia’, corresponding to the island now normally referred to as ‘Trangan’ in the Aru Islands group, eastern Indonesia.

The islands are located in the Arafura Sea, with western New Guinea to the north and the Arnhem Land Region of Australia’s Northern Territory to the south, and though they lie within Maluku province of eastern Indonesia, are part of the Australian continent in a geological sense.

This species is also traded as ‘forktail rainbowfish’ or ‘yellow forktail’, and it’s also undergone several changes in scientific name since description. Pseudomugil furcatus is the original designation, but Allen (1980) created the genus Popondetta for it on the basis of morphological characters including number of anal-fin rays (16-20 in P. furcatus, 8-12 in other Pseudomugil spp.), absence of anterior…

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 …