How to Identify Molly

To identify Molly (Poecilia), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Wild-type mollies are typically silvery-grey to olive-green, often with iridescent scales. Domesticated varieties exhibit a vast array of colors including black (Black Molly), white, gold, orange, red, dalmatian (black spots on white/silver), marble, and various combinations. Some have metallic sheens.

Scale type

cycloid

Mouth position

superior

Distinctive features

Sexual dimorphism: Males are generally smaller, more slender, and possess a modified anal fin called a gonopodium for internal fertilization. Females are larger, rounder, and lack a gonopodium., Sailfin varieties (P. latipinna, P. velifera) have greatly enlarged dorsal fins in males, resembling a sail., Short-finned varieties (P. sphenops) have a more typical, rounded dorsal fin.

Dorsal fin

Single dorsal fin, typically rounded in P. sphenops, greatly elongated and sail-like in male P. latipinna and P. velifera. Contains 8-19 rays depending on species.

Tail fin

Caudal fin is typically rounded or lyre-shaped in some cultivated varieties.

Pectoral fin

Paired pectoral fins, typically small and rounded.

Distinctive fins

Anal fin of males is modified into a gonopodium for reproduction. Pelvic fins are small and located abdominally.

Identification Tips

1. 1

   Body Shape and Size

   Look for a moderately compressed body. P. sphenops typically reaches 5-8 cm (2-3 inches), while P. latipinna can reach 10-12 cm (4-5 inches) and P. velifera up to 15 cm (6 inches).

2. 2

   Fin Morphology

   Observe the dorsal fin. If it's exceptionally large and sail-like, it's likely a male Sailfin Molly (P. latipinna or P. velifera). The anal fin of males is a distinct, rod-like gonopodium.

3. 3

   Coloration

   While highly variable due to breeding, wild types are generally drab. Domesticated varieties come in almost any color. Black Mollies are easily identifiable by their solid black pigmentation.

4. 4

   Mouth Position

   Mollies have an upturned mouth, indicating their surface-feeding habits, often grazing on algae and detritus.

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