Wagtail Platy Platy
Xiphophorus maculatus
About this strain
Defined by jet-black fins — dorsal, caudal, anal, and pectoral — set against a contrasting body color that can range from red and gold to blue or white depending on the base strain it's crossed with. The all-black finnage is the defining character here; a true Wagtail should have fully melanized fins without patchiness. The body color itself is secondary — you'll often see 'Red Wagtail' or 'Sunset Wagtail' named for the base. This is a pattern gene, not a color variety, so mixing Wagtail with other strains is straightforward and commonly done by hobbyists.
Origin
The Wagtail pattern was first described and selectively bred in the early-to-mid 20th century. It appears in genetics literature from the 1930s onward. Commercial stabilization as a distinct trade variety occurred across European and American fish farms by the mid-century.