Poecilia velifera

__NOTOC__Taxobox
name = Yucatan molly

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image_width = 250px
regnum = Animalia
phylum = Chordata
classis = Actinopterygii
ordo = Cyprinodontiformes
familia = Poeciliidae
genus = "Poecilia"
species = "P. velifera"
binomial = "Poecilia velifera"
binomial_authority = (Regan, 1914)

"Poecilia velifera", the Yucatan Molly, lives in coastal waters of the Yucatan peninsula. These live-bearer (Poeciliidae) fish are particularly well known for both the extreme size variation among males, and the sexual dimorphism between males and females in both body shape and behavior.

It is outwardly similar to the sailfin molly, "P. latipinna", though larger overall and with a higher and longer dorsal fin in males. Full-grown fish are usually larger than 10 cm/4 in, though especially captive-bred individuals grow only to the size of sailfin mollies. The dorsal fins are the most distinctive character for telling the species apart: Those of the Yucatan molly have nearly 20 fin rays, counting where the fin meets the back, whereas the sailfin molly has less than 15 (intermediate numbers may indicate hybrids).

If the males spread their dorsal fin in display, these have a distinct fan- or trapezoid shape, with the upper edge being distinctly longer than the lower. The height of the dorsal fin, measured at the posterior edge, is a bit larger than the height of the tail.

Common names

Yucatan molly, "Sailfin molly" (erroneous) (English), Segelkärpfling (German), Hoogvinkarper Dutch, Molinezja żaglopłetwa (Polish), セイルフィン モーリー ("seirufuin mōrī", Japanese) and molliénésie á voilure or simply "molly voile" (French),Molinésia Velífera (Portuguese).