Sailfin Molly, Poecilia latipinna
Sailfin Molly, Poecilia latipinna, Female. Fish caught out from the Meadow Hotsprings, Meadow, Utah, July 2021. Length: 7.6 cm (3.0 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.
Sailfin Molly, Poecilia latipinna, Male. Fish caught from Fish caught out from the Meadow Hotsprings, Meadow, Utah, July 2021. Length: 7.8 cm (3.1 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.
The Sailfin Molly, Poecilia latipinna, is a member of the Livebearer or Poeciliidae Family, that is known in Mexico as topote velo negro. Globally, there are forty species in the genus Poecilia, of which six are found in Mexican freshwater systems that drain into both the Atlantic and the Pacific Oceans. The Sailfin Molly is closely related to the Mexican Molly, Poecilia sphenops.
The Sailfin Molly has an oblong moderately robust body that is compressed at the rear. They vary in color but are generally light gray with several rows of spots along the sides, back and dorsal fin which can appear as stripes; they transition to lighter ventrally. The spots on the dorsal fin are dark and rectangular in shape. The caudal fins have rows of brown spots with central orange parts and a black with a white rear boarder. Some fish have black tipped caudal fins. There fins are transparent with small spots along the rays. There are also albino, leucitic, melanistic (the Midnight Molly) and speckled forms. The breeding males are greenish-blue with large long, colorful sail-like dorsal fins and very colorful orange caudal fins. Their heads are small and dorsally flattened with a small, upturned mouth that opens at the front and equipped with many rows of very small teeth. They have 8 or 9 anal fin rays; broad caudal peduncles; large, rounded, caudal fins; their single dorsal fin has 13 to 16 rays with a short base that is located at the rear of the body originating over the pelvic fin origin; and, their pelvic fins that are small and originate behind the pectoral base. They have 22 to 27 gill rakers. The Sailfin Molly is sexually dimorphic with females (15 cm or 5.9 inches) being larger than males (10 cm or 3.9 inches) with smaller less colorful dorsal fins. The males also have a modified anal fin known as a gonopodium that functions as a sex organ during mating. They are covered with small large scales.
The Sailfin Molly is a non-migratory benthopelagic species that are found in small to large aggregations in both coastal brackish and freshwater habitats in springs, lakes and ponds, backwaters and pools of streams, drainage ditches, and salt marshes in shallow water that is heavily vegetated at depths up to 3 m (10 feet) in water temperatures between 20°C (68°F) and 28°C (82°F) with salinities up to 87 ppt. They are able to source oxygen from the water surface and can survive in oxygen-depleted habitats and heavily polluted waters. Reproduction occurs primarily in brackish waters and involves internal fertilization with gestation periods of 3 or 4 weeks. The males display their large trapezoid dorsal fins to attract females. Each female can produce broods of 10 to 140 live young several times each year. The females have the ability to store sperm and give birth on multiple occasions throughout the year. They are known to interbreed with the Black Molly, Poecilia sphenops. They are omnivorous that feed on algae and other plant materials as-well-as aquatic invertebrates, including mosquito larvae. In turn they are preyed upon amphibians, aquatic insects, birds, fishes, mammals and reptiles. Females have life spans of three years and males less than two years with native populations having larger populations of females than males.
The Sailfin Molly is similar and easily confused with the Yucatán Molly, Poecilia velifera (larger in stature; light colored rounded spots on the dorsal fin; 18 to 19 dorsal rays).
The Sailfin Molly is a resident of the coastal freshwater systems along the Atlantic Slope from the Texas border to the Yucatán Peninsula in the states of Campeche, Nuevo León, Quintana Roo, Tabasco, Tamaulipas, Veracruz, and Yucatán.
From a conservation perspective the Sailfin Molly is currently considered to be of Least Concern with stable, widely distributed populations. In some areas they are threatened via human development causing the loss of native habitat. They have been introduced throughout the world from escapes, intentional releases from fish farms to control mosquito populations, and releases by aquarists raising havoc of native fishes and their environments. The Sailfin Molly has been utilized as an indicator species to show impacts from pollution including pesticides and other chemicals. Their long-term survival in certain areas is threatened by human development. In some locations have been introduced to control mosquito populations and have quickly become a nuisance pest causing ecological damage due to their ability to rapidly reproduce in high numbers. The Sailfin Molly is a popular aquarium fish as they can be bred in captivity in a wide variety of colors.