Taxonomy
- Kingdom: Animalia
- Phylum: Chordata
- Class: Actinopterygii
- Order: Cyprinodontiformes
- Family: Poeciliidae
- Genus: Poecilia
- Species: P. sphenops
Common name
Black molly (also called short-finned molly).
Description
Poecilia sphenops is a small live‑bearing freshwater fish, typically reaching 4–10 cm in total length, though females may grow slightly larger than males. The species exhibits sexual dimorphism: males are generally more brightly colored, with a more elongated dorsal fin, while females display a broader, more rounded body and a prominent gonopodium (modified anal fin) used for internal fertilization. The species’ coloration ranges from silvery gray to dark gray or black, often with subtle blue or green iridescence.
Distribution and habitat
Native to Central America, P. sphenops occurs in the Atlantic slope of Mexico, Guatemala, Belize, Honduras, and Nicaragua. It inhabits a variety of freshwater environments, including rivers, streams, lagoons, marshes, and brackish coastal waters. The species tolerates a wide range of water parameters, with optimal temperatures of 22–28 °C (72–82 °F) and pH 7.0–8.0, and can survive in mildly saline conditions up to 10 ppt.
Ecology and behavior
P. sphenops is omnivorous, feeding on algae, detritus, small invertebrates, and biofilm. It displays a shoaling tendency, often forming small groups in the wild. The species is a live‑bearer; gestation lasts approximately 21–30 days, after which females give birth to 20–80 fully formed fry. Reproduction can occur year‑round in suitable conditions.
Conservation status
The International Union for Conservation of Nature (IUCN) has not evaluated Poecilia sphenops separately; the species is generally considered common throughout its range and not subject to major threats. However, localized habitat degradation and water pollution could impact specific populations.
Aquarium trade
Poecilia sphenops is popular in the ornamental fish industry due to its hardiness, tolerance of variable water conditions, and ease of breeding. In captivity, it thrives in community tanks with well‑maintained water quality, moderate lighting, and ample plant cover. The species can adapt to both freshwater and brackish setups, and is often used in educational and research settings because of its live‑bearing reproductive mode.
References
- FishBase. Poecilia sphenops. https://www.fishbase.de/
- World Register of Marine Species (WoRMS). Poecilia sphenops (Günther, 1866). https://www.marinespecies.org/
- IUCN Red List (search for Poecilia species).
Note: All information presented is derived from established ichthyological sources and scientific literature.
