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Rio Chihuahua [Rio Grande drainage], Mexico (Girard 1859).
Etymology/Derivation of Scientific Name
Gambusia senilis Girard 1859:121-122.
Maximum size: 55 mm TL (Page and Burr 1991).
Coloration: Lateral stripe broad; markings on sides crescentric; dorsal and (in females) anal fins with yellow pigmentation (lost in preservation); dusky lateral stripe pronounced; mouth with dark markings or anal spot of females restricted to area immediately around anus; predorsal stripe thin or absent (Hubbs et al. 2008). Page and Burr (1991) described coloration: dusky stripe (about 1 scale deep) along side, dark scale outlines (often appearing as black cresents) and black spots (often poorly developed on male) on lower side. Usually a large black teardrop. Dusky olive above, dark stripe along back to dorsal fin; silver side; light yellow median fins, small dusky spots near base of dorsal fin. No dark anal spot; no spots on caudal fin. Individuals in some populations have scattered large black spots on body (Page and Burr 1991).
Counts: Dorsal fin rays 7-8 (Hubbs et al. 2008).
Body shape: Pectoral fin of males with slight indentation, shallower than widest pectoral fin ray; dorsal fin origin well behind anal fin origin (Hubbs et al. 2008).
External morphology: Elbow of gonopodium composed of usually 4 fused segments; tip of anterior branch of 4th ray of male gonopodium does not extend to tip of posterior branch; distal segments of anterior branch of 4th fin ray of gonopodium not coalesced to elbow; spines at tip of 3rd anal fin ray of male gonopodium 4-10 times longer than wide (Hubbs et al. 2008).
Internal morphology: Intestinal canal short with few convolutions (Hubbs et al. 2008).
Distribution (Native and Introduced)
U.S. distribution: Primarily found within the Rio Conchos drainage of Chihuahua, Mexico; known from the Devils River in Texas (Hubbs and Springer 1957; Hubbs 1958; Hubbs et al. 2008).
Texas distribution: The population once known from the Devils River has likely been extirpated (Hubbs et al. 2008).
Abundance/Conservation status (Federal, State, NGO)
State Threatened (Texas; Hubbs et al. 2008). Gambusia senilis was probably extirpated in the Devils River, Texas following the construction of Amistad Reservoir (Hubbs et al. 1991; Garrett and Edwards 2001; Edwards et al. 2002, 2004; Hubbs et al. 2008). Gambusia senilis listed as Threatened by the American Fisheries Society; status has declined since 1989; categories of threats: present or threatened destruction, modification, or reduction of habitat or range; and other natural or anthropogenic factors that affect the existence of this species, including impacts of nonidigenous organisms, hybridization, competition, and/or predation (Jelks et al. 2008). Common in the Rio Conchos and its tributaries in Chihuahua, Mexico (Edwards et al. 2004). According to Edwards et al. (2002), Gambusia senilis was generally abundant and widely distributed in Mexican samples. The Rio Grande Fishes Recovery Team has recommended reestablishment of the Texas population in Devils River State Natural Area from stocks in the Rio Chuviscar (Edwards et al. 2002). Gambusia senilis is a protected species in Mexico (Garrett and Edwards 2001). Page and Burr (1991) reported Gambusia senilis as extinct in the United States; common in the Rio Conchos drainage, Mexico. Minckley et al. (1991) stated that Gambusia senilis was likely secure due to wide distribution. Guillory (1980) noted that the species was widely distributed in the Rio Conchos (Mexico) but limited in the Devils River (Texas). See also Contreras-Balderas (1974) and Minckley and Koehn (1965).
Macrohabitat: Stream channels, edges, backwaters; springs, outflows, marshes (Minckley et al. 1991). Springs; vegetated quiet pools and backwaters (Page and Burr 1991).
Mesohabitat: Usually collected in quiet, weed-choked surface waters, although tolerant of wide variations in temperature, chemical conditions, and water flow and clarity (Guillory 1980); eurythermal (Minckley et al. 1991).
Age at maturation:
Growth and Population structure:
Phylogeny and morphologically similar fishes
Gambusia senilis is similar to both the Big Bend gambusia (G. gaigei) and the Amistad gambusia (G. amistadensis); Page and Burr (1991) noted that the latter two species differ from G. senilis in that they lack prominent black marks on lower side, and females of each species have a dark anal spot.
Gambusia senilis is a member of the G. senilis species group (Rivas 1963; Rauchenberger 1989). Formerly, Gambusia senilis was recognized as a member of the G. nobilis species group, with closest affinities to allopatric Pecos gambusia (G. nobilis; Hubbs and Springer 1957; Rosen and Bailey 1963; Guillory 1980).
The tapeworm Bothriocephalus acheilognathi reported from Gambusia senilis, in Mexico (Martinez-Aquino and Aguilar-Aguilar 2008).
Commercial or Environmental Importance
[Additional literature noting collection of this species from Texas locations includes, but is not limited to the following: Garrett et al. (1992).]
Contreras-Balderas, S. 1974. Speciation aspects and man-made community composition changes in Chihuahuan Desert fishes. In: Wauer, R.H., and D.H. Riskind (eds.). Transactions of the Symposium on the Biological Resources of the Chihuahuan Desert Rigion United States and Mexico. U.S. Department of the Interior, National Park Service Transactions and Proceedings Series (3):405-431.
Edwards, R.J., G.P. Garrett, and E. Marsh-Matthews. 2002. Conservation and status of the fish communities inhabiting the Conchos basin and middle Rio Grande, Mexico and U.S.A. Reviews in Fish Biology and Fisheries 12:119-132.
Edwards, R.J., G.P. Garrett, and N.L. Allan. 2004. Aquifer dependent fishes of the Edwards Plateau region, Chapter 13. pp. 253-268 in: Mace, R.E., E.S. Angle, and W.F. Mulligan, III (Eds.). Aquifers of the Edwards Plateau. Texas Water Development Board. 360 pp.
Garrett, G.P., and R.J. Edwards. 2001. Regional ecology and environmental issues in West Texas, Chapter 5. pp. 56-65 in: Mace, R.E., W.F. Mullican, Jr., and E.S. Angle (Eds.). Aquifers of West Texas. Texas Water Development Board.
Garrett, G.P., R.J. Edwards, A.H. Price. 1992. Distribution and status of the Devils River minnow, Dionda diaboli. The Southwestern Naturalist 37(3):259-267.
Girard, C. 1859. Ichthyological notices. Proc. Acad. Nat. Sci. Phila. 11:113-122.
Guillory, V. 1980. Gambusia senilis (Girard), Blotched gambusia. pp. 546 in D. S. Lee et al., Atlas of North American Freshwater Fishes. N. C. State Mus. Nat. Hist., Raleigh, i-r+854 pp.
Hubbs, C. 1958. Gambusia senilis from the Devil's River, Texas, an addition to the fish fauna of the United States. Copeia 1958(3):239.
Hubbs, C., and V.G. Springer 1957. A revision of the Gambusia nobilis species group, with descriptions of three new species, and notes on their variation, ecology and evolution. Texas Journal of Science 9(3):279-327.
Hubbs, C., R J. Edwards, and G.P. Garrett. 1991. An annotated checklist of the freshwater fishes of Texas, with keys to identification of species. The Texas Journal of Science, Supplement 43(4):1-56.
Hubbs, C., R.J. Edwards, and G.P. Garrett. 2008. An annotated checklist of the freshwater fishes of Texas, with keys to identification of species. Texas Journal of Science, Supplement, 2nd edition 43(4):1-87.
Jelks, H.L., S.J. Walsh, N.M. Burkhead, S. Contreras-Balderas, E. Diaz-Pardo, D.A. Hendrickson, J. Lyons, N.E. Mandrak, F. McCormick, J.S. Nelson, S.P. Platania, B.A. Porter, C.B. Renaud, J.J. Schmitter-Soto, E.B. Taylor, and M.L. Warren, Jr. 2008. Conservation status of imperiled North American freshwater and diadromous fishes. Fisheries 33(8):372-407.
Martinez-Aquino, A., and R.Aguilar-Aguilar. 2008. Helminth parasites of the pupfish Cyprinodon meeki (Pisces: Cyprinodontiformes), an endemic freshwater fish from North-Central Mexico. Helminthologia 45(1):48-51.
Minckley, W.L., and R.K. Koehn. 1965. Re-discovery of the fish fauna of the Sauz Basin, Northern Chihuahua, Mexico. The Southwestern Naturalist 10(4):313-315.
Minckley, W.L., G.K. Meffe, and D.L. Soltz. 1991. Conservation and management of short-lives fishes: the Cyprinodontoids, Chapter 15. pp. 247-282 in: Minckley, W.L., and J.E. Deacon (Eds.). Battle Against Extinction: Native Fish Management in the American West. University of Arizona Press, Tucson, Arizona. 517 pp.
Page, L. M. & B. M. Burr. 1991. A field guide to freshwater fishes of North America north of Mexico. Houghton Mifflin Company, Boston, Massachusetts. 432 pp.
Rauchenberger, M. 1989. Systematics and biogeography of the genus Gambusia (Cyprinodontiformes: Poeciliidae). American Museum Novitates 2951:1-74.
Rivas, L.R. 1963. Subgenera and species groups in the poeciliid fish genus Gambusia Poey. Copeia 1963(2):331-347.
Rosen, D.E, and R.M. Bailey. 1963. The poeciliid fishes (Cyprinodontiformes): their structure, zoogeography, and systematics. Bull. Am. Mus. Nat. Hist. 126:1-176.