Although it does penetrate the lower basins of rivers, particularly the Amazon where it has been collected from the rio Xingu several hundred kilometres from its mouth, this species is predominantly an inhabitant of mangrove swamps, estuaries, and other such saline habitats.

It is particularly common in tidal channels, shallow inshore lagoons, and the lower reaches of rivers.

Tends to be most common in brackish to hypersaline environments such as coastal salt marshes, lagoons and estuaries.

On San Salvador Island, Bahamas, it appears to be the parent of a species group occurring in sympatry and exploiting diverse but specific resources with some spectacular morphological adaptations.

Endemic to San Salvador Island in the Bahamas where it’s known from six hypersaline lakes; Crescent Pond, Osprey Lake, Oyster Lake, Little Lake, Wild Dilly Pond and Moon Rock Pond.

Type locality is ‘San Salvador Island, Bahamas: Crescent Pond, 1 km SE of the Gerace Research Centre, lat 24°06’45″N, long 74°27’28″W’.

This species is a specialised lepidophage with approximately 50 % of the diet comprising the scales of other fishes.

Physical adaptations to this behaviour include its elongate body and jaw mechanism permitting a fast biting action.

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 …