Poecilia mexicana
Shortfin Molly
NS
G5
Collection Details
Specimens
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Taxonomic Hierarchy
Actinopterygii (Ray-finned Fishes)
Cyprinodontiformes
Poeciliidae (Livebearers)
Poecilia
Poecilia mexicana (Shortfin Molly)
Description
This species account was compiled from
Composite (multiple sources) (McEachran, J.D. and J.D. Fechhelm. Fishes of the Gulf of Mexico. University of Texas Press, Austin.)
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Characters
Moderately robust, straight to slightly convex dorsal profile, relatively short dorsal fin, and relatively deep caudal peduncle. Snout is acute and of moderate length. Mouth is oblique and very small. Jaws have outer row of small, conical, recurved, unicuspid teeth and inner band of villiform teeth. Gill rakers on first arch number 21 to 26. In males, snout length is 7.1% to 8.9%, head length is 22.9% to 26.4%, body depth is 26.1% to 28.5%, snout to dorsal fin origin is 54.6% to 58.7%, snout to anal fin origin is 51.2% to 55.2%, and caudal peduncle depth is 17.6% to 18.4% of SL. In females, snout length is 7.5% to 8.4%, head length is 23.9% to 24.9%, body depth is 26.5% to 29.4%, snout to dorsal fin origin is 58.5% to 59.1%, snout to anal fin origin is 61.5% to 64.6%, and caudal peduncle depth is 16.6% to 18.1% of SL. Pectoral fin is located just below midflank and has 13 to 15 rays. Dorsal fin originates posterior to pelvic fin insertion and anterior to vent, and has 8 to 11 rays. Pelvic fin of mature males has fleshy swelling on distal section of ray 1; long, fleshy extension of ray 2 and rays 1 and 2 are joined by dense connective tissue and separated from rays 3, 4, and 5 by notch. Anal fin originates under anterior one-half of dorsal fin base and has 7 or 8 rays. Gonopodium in males is formed by enlarged third, fourth, and fifth anal fin rays. Third ray bears fleshy palp on ventral surface and short retrorse spines near tip. Ray 5a has small retrorse claw at tip, and tough, membranous or bony hook projects ventrally from tip of ray 3. Ray 5b extends to within two or three segments of ray 5a. Lateral scale rows number 28 to 30.
Color is variable, light brownish green to light brownish gray dorsally and pale
Distribution
North and Central America: Rio San Juan, Mexico to Guatemala. At least one country reports adverse ecological impact after introduction.
Habitat Associations
Freshwater, brackish. benthopelagic.
Biology
Occurs in warm springs and their effluents, canals and weedy ditches, and stream pools (Ref. 5723). Food is mainly detritus (Ref. 36880). Some populations in caves (Ref. 27297).
Max length: 11.0 cm SL; common length: 4.0 cm TL.
Reproductive mode: dioecism; fertilization: internal (oviduct); bearers (internal live bearers). 28 days after fertilization female gives birth to 30-80 young. Sexual maturity is reached after 7-12 months (Ref. 2060).
IUCN Red List Status: Least Concern (LC), assessed 2018-03-22. Resilience: Medium (Preliminary K or Fecundity.).
Phylogeny and Morphologically Similar Fishes
Distinguished from the other species of the family by the combination of characters described
Commercial or Environmental Importance
Fisheries: of no interest; aquarium: commercial.
References
Page, L.M. and B.M. Burr (1991) A field guide to freshwater fishes of North America north of Mexico. Houghton Mifflin Company, Boston. 432 p.
Wischnath, L. (1993) Atlas of livebearers of the world. T.F.H. Publications, Inc., United States of America. 336 p.
Proudlove, G.S. (1997) A synopsis of the hypogean fishes of the world. p. 351-354. In Proceedings of the 12th International Congress of Speleology, La Chaux de Fonds, Switzerland. vol. 3.
Greenfield, D.W. and J.E. Thomerson (1997) Fishes of the continental waters of Belize. University Press of Florida, Florida. 311 p.
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