Almost. For strainbred varieties you can add "var. + (name)". It's more common among botanists, but it's becoming more and more frequent in fishkeeping due to the number of domestic strains available nowerdays. You can only use this for standard defined and stable strains.I'd say Poecilia Sphenops
They are bred to have all kinds of different looks but all fall under the same name. This means trade names may be more useful in finding the fish you want than scientific name are.
Canis Domesticus covers all domestic dogs, which also vary greatly in appearance.
How about a photo?