San Marcos gambusia
Encyclopedia
The San Marcos gambusia is an endangered species
of fish
, found only in the San Marcos Springs
of Central Texas
. The fish has not been seen since 1983, so it may be extinct.
usually has a dark stripe along its edge. The species’ exact diet is not known, but other poeciliids typically eat insect
larvae and other small invertebrate
s.
The fish are live bearing, and have been known to give birth to a few dozen young at a time.
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 appear to need clean and clear water, with little temperature variability. They apparently also prefer shallow, quiet water, along with partial shade.
Endangered Species Act
The Endangered Species Act of 1973 is one of the dozens of United States environmental laws passed in the 1970s. Signed into law by President Richard Nixon on December 28, 1973, it was designed to protect critically imperiled species from extinction as a "consequence of economic growth and...
of fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
, found only in the San Marcos Springs
San Marcos Springs
San Marcos Springs is the second largest natural cluster of springs in Texas. The springs are located in the city of San Marcos, Texas, about 30 miles southwest of Austin and 46 miles northeast of San Antonio.-Geology:...
of Central Texas
Central Texas
Central Texas , is a region in the U.S. state of Texas. It is roughly bordered by San Marcos to Fredericksburg to Waco, and to Brenham, and includes the Austin–Round Rock, Killeen-Temple-Fort Hood, Bryan-College Station, and Waco metropolitan areas...
. The fish has not been seen since 1983, so it may be extinct.
Description
The San Marcos gambusia is typically less than 1.6 inches (4 cm) in length. It frequently has a dark body with a slight blue tint, although the median fins are often yellow. The scales are strongly crosshatched, and the dorsal finDorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
usually has a dark stripe along its edge. The species’ exact diet is not known, but other poeciliids typically eat insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
larvae and other small invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s.
The fish are live bearing, and have been known to give birth to a few dozen young at a time.
Habitat
San Marcos River
The San Marcos River rises from the San Marcos Springs, the location of Aquarena Springs, in San Marcos, Texas. The springs are home to several threatened or endangered species, including the Texas Blind Salamander, Fountain Darter, and Texas Wild Rice...
. They appear to need clean and clear water, with little temperature variability. They apparently also prefer shallow, quiet water, along with partial shade.
External links
- San Marcos gambusia (Gambusia georgei) page from the Texas Parks and Wildlife Department
- San Marcos gambusia page from http://www.edwardsaquifer.net/
- Information from the U.S. Fish and Wildlife Service