San Marcos gambusia

The San Marcos gambusia (Gambusia georgei) is an extinct species of gambusia from the family Poeciliidae that was found only in the San Marcos Springs of Central Texas.[2] The fish has not been seen since 1983.[1] The specific name of this fish honors the American ichthyologist George S. Myers (1905-1985).[3]

San Marcos gambusia
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cyprinodontiformes
Family: Poeciliidae
Genus: Gambusia
Species:
†G. georgei
Binomial name
†Gambusia georgei
C. Hubbs & Peden, 1969

Description

The San Marcos gambusia was typically less than 1.6 inches (4 cm) in length. It had a dark body with a slight blue tint, although the median fins were lemon yellow. The scales were strongly crosshatched, and the dorsal fin had a dark stripe along its edge. The species’ exact diet is not known, but other poeciliids typically eat insect larvae and other small invertebrates. The fish were live bearing, and have been known to give birth to a few dozen young at a time.[4]

Habitat
Downstream from the headwaters of the San Marcos Springs, Aquarena Springs, and Spring Lake

The San Marcos gambusia has only been identified in a 0.6-mile (1-km) stretch of the headwaters of the San Marcos River. They appeared to need clean and clear water, with little temperature variability. They apparently also preferred shallow, quiet water, along with partial shade.[1]

Extinction

As of 1969, the population was less than 1,000 individuals. The species was threatened by reduced spring flows and pollution, including sprayed herbicide along the river and introduced fish (Gambusia affinis) and plants (Colocasia esculenta). As no specimens have been sighted since 1983, the species is now considered extinct.[1]

References
  1. NatureServe (2013). "Gambusia georgei". IUCN Red List of Threatened Species. 2013: e.T8891A18233501. doi:10.2305/IUCN.UK.2013-1.RLTS.T8891A18233501.en.
  2. Froese, Rainer and Pauly, Daniel, eds. (2006). "Gambusia georgei" in FishBase. August 2006 version.
  3. Christopher Scharpf; Kenneth J. Lazara (26 October 2019). "Order CYPRINODONTIFORMES: Families POECILIIDAE, ANABLEPIDAE, VALENCIIDAE, APHANIIDAE and PROCATOPODIDAE". The ETYFish Project Fish Name Etymology Database. Christopher Scharpf and Kenneth J. Lazara. Retrieved 2 November 2019.
  4. "Endangered Species of the Edwards Aquifer - Gambusia georgei". The Edwards Aquifer Website.
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