Edwards Aquifer Species Scientific Name: San Marcos Salamander – Eurycea nana, Texas Blind Salamander – Typhlomolge rathbuni, San Marcos Gambusia – Gambusia georgei, Fountain Darter – Etheostoma fonticola, Peck’s Cave Amphipod – Stygobromus pecki, Comal Springs Riffle Beetle – Heterelmis comalensis, Comal Springs Dryopid Beetle – Stygoparnus comalensis Federal Status: Endangered except for the San Marcos Salamander, which is listed as Threatened • State Status: Endangered except for the San Marcos Salamander, which is listed as Threatened Description of Species, stant temperature is required for suit- Habitats and Life able habitat. San Marcos Salamanders feed on History amphipods (tiny aquatic crustaceans), The San Marcos Salamander is aquatic insects, and small aquatic small and slender, with a total length snails. Breeding is thought to occur of about 2.5 inches. It is uniformly throughout the year with a possible light brown to golden brown, with peak in May and June. small yellow flecks along each side of The Texas Blind Salamander the back. The underside of its body occurs only in the subterranean is yellowish-white. A member of the waters of the Edwards aquifer near brook salamander group, the San San Marcos Salamander San Marcos, Texas. Because it is © ?????????? Marcos Salamander has external gills, adapted to living in a subterranean which are retained throughout life. environment, it lacks eyes and has lit- It has relatively short slender legs, tle skin pigment. It is all white, with with four toes on the fore feet and blood-red external gills and toothpick- five on the hind feet. It has a slender tail with a well developed and dorsal or top fin. Present Range for The San Marcos Fountain Darter Salamander occurs only in Spring Lake and an adjacent downstream portion Texas Blind Salamander © ????????? of the upper San Marcos River. They are most often found in spring areas with a substrate of sand and gravel, and larger rocks interspersed with large limestone Present Range for Texas Blind Salamander, San boulders. These boul- Marcos Salamander and ders in shallow water San Marcos Gambusia support a lush growth of aquatic moss. like legs. The head and snout of this Interspersed with the moss and cover- salamander are strongly flattened, San Marcos Gambusias ing the shallow sandy substrate are © Bob Edwards with two vestigial eyes (appearing as thick mats of coarse filamentous blue- black dots) beneath the skin. Its green algae. The dark reddish-brown total length is about 5 inches. color of this alga almost perfectly This salamander is strictly matches the dark dorsal color of the aquatic, and lives in the water-filled San Marcos salamander. Vegetative caverns in the San Marcos Pool of cover is important for protection and the Edwards aquifer. It requires for providing habitat for living organ- clean water of relatively constant isms that serve as food for the sala- temperature. mander. This species does not The Texas Blind Salamander inhabit areas with a sandy bottom feeds on a variety of small subter- devoid of vegetation, nor do they ranean aquatic organisms, including occur where the bottom is muddy, Fountain Darters whether or not vegetation is present. © Glenn Longley Clean, clear, flowing water of con- Edwards Aquifer Species 1 tiny snails, amphipods, and shrimp. The San Marcos Gambusia When feeding, the salamanders probe prefers shallow, quiet waters adjacent the bottom using lateral movements to sections of flowing water. of the head. When anything living is Constant water temperature is also encountered, the mouth quickly opens very important. This fish prefers a and the food item is immediately muddy, but not silted, bottom. Partial sucked into the mouth. Numerous shade from bridges or overhanging sharp teeth prevent the prey from vegetation also seems to be an impor- escaping. It is thought that sensitivity tant habitat factor. to water vibrations also helps these There is little information on the salamanders locate food. food habits or reproduction of this Although courtship and repro- species. It is thought that insect lar- Peck’s Cave Amphipod ductive behavior have been observed vae and other invertebrates comprise © Jean Krejca and recorded for captive specimens, most of the diet. little information exists regarding The Fountain Darter is a small reproduction of the Texas Blind fish, usually about 1 to 2 inches in Salamander in its natural habitat. length, found only in the San Marcos Females with eggs and juveniles have and Comal River headwaters. It is been observed throughout the year, reddish-brown with fine specks in the so it is thought that reproduction dorsal region. A series of horizontal occurs year-round. stitch-like dark lines occur along the The Texas Blind Salamander is middle of the sides, forming an inter- at the top of the food chain in a very rupted lateral streak. There are three unique community of subterranean small dark spots on the base of the organisms living in the Edwards tail, and one on the opercle (flap Aquifer. This aquifer has exhibited covering the gills). Dark bars appear the greatest diversity of any know in front of, below, and behind the aquifer system. There are forty plus eye. The lower half of the dorsal fin species living in the aquifer with the is black, above this is a broad red Comal Springs Riff le Beetle salamander, and most of them are band, and above this the fin is edged © Jean Krejca just as endangered as the salamander. in black. If any of the species are lost from the The Fountain Darter prefers system it will have an effect on the vegetated stream-floor habitats with a Texas Blind Salamander. One of the constant water temperature. They are greatest threats to the Aquifer system most often found in and among is the potential for over pumping rooted aquatic plants, mosses, and which may allow saline water to algae. They are occasionally found in enter areas that are now fresh water. areas lacking vegetation. Young One of the rarest animals of the Fountain Darters are found in heavily San Marcos River, and one which may vegetated, backwater areas of the San already be extinct, is the San Marcos Marcos and Comal Rivers where there Gambusia. Last collected in the wild are low water velocities. Adults occur in 1983, this fish is a member of a in all suitable habitats, including genus having more than 30 species of riffles. Fountain Darters feed on cope- live bearing freshwater fishes. It is a pods (tiny aquatic crustaceans) and small fish, about 1 inch in length, mayfly larvae. They feed primarily known only from the upper San during the day, and show selective Marcos River. This species is plainly feeding behavior. Observations sug- Comal Springs Dryopid Beetle marked and similar in appearance to © Jean Krejca gest that darters feed on small mov- the western mosquitofish (Gambusia ing aquatic animals, while ignoring additional collections of this species affinis). It has a prominent dark immobile ones. have not been made at this location. stripe along the upper edges of the The adult Comal Springs Riffle Comal Springs riffle beetle is highly dorsal fin. The unpaired fins tend to Beetle has a narrow body about dependent on the constant and nar- be yellow or yellowish-orange. A 2 mm long, and it is reddish-brown in row range of habitat conditions associ- bluish sheen is evident near the head, color. The larva has an elongate, ated with the springs-flows issuing especially in more darkly pigmented tubular body and can be up to 10 mm from the Edwards Aquifer. Larval and adult females. The anal fin of in length. The Comal Springs riffle adult riffle beetles both feed on Gambusia males is modified into a beetle is known primarily from Comal microorganisms and debris scraped tube-like structure called a Springs where it has been collected from the substrate. However, the spe- gonopodium. The gonopodium is from only the primary spring-runs cific feeding habits of this riffle beetle used to transfer sperm from the male and from up-wellings underlying are unknown. All beetles (Coleoptera) to the female. Landa Lake. A single specimen of this are holometabolous and have com- species was taken from the plete life cycles consisting of an egg, 2 Edwards Aquifer Species impounded San Marcos Springs, but larva with multiple instars, pupa, and associated habitats at Comal Springs, requirements for these listed species. New Braunfels, Texas, and Fern Bank The danger of reduced spring flow is Springs near Wimberley, Texas. Some the most serious threat to the contin- specimens have been found in the ued existence of the San Marcos and upper spring-runs at Comal Springs, Comal Rivers and their endemic but they are thought to have been plants and animals. flushed from the Aquifer. Adults and The effects of periodic drought larvae of this species have been col- coupled with increased groundwater lected with drift nets placed over the use are a serious threat. For exam- springs sources at Comal Springs and ple, a severe drought from 1950-1956 in the upper portions of each spring- greatly reduced the aquifer level and run. The specific micro-habitat this spring discharges. During 1956, species inhabits is unknown. Comal Springs ceased to flow for five However, larvae of other dryopid months. Less severe droughts in species are semi-aquatic or terrestrial 1984 and 1990 resulted in minimum and the larvae of the Comal Springs daily flows at Comal Springs of 24 dryopid beetle may inhabit the ceil- cfs (cubic feet per second) and 46 cfs, ings of the spring openings. These respectively, compared to the mean spring openings typically have soil, spring flow discharge (1933-1990) of roots and debris exposed above the 293 cfs.