Barton Springs Salamander

The Barton Springs salamander inhabits water of high quality maintained by groundwater sourced from the Barton Springs Segment of the Edwards Aquifer. The Edwards Aquifer is characterized by open chambers such as caves, fractures and other cavities that were formed either directly or indirectly by the dissolution of subsurface rock formations. Surface water filters through the soil and recharge features like caves, faults, fractures, sinkholes or other open cavities, into the Edwards Aquifer and then it discharges from springs as groundwater. The Barton Springs salamander is typically found in surface habitats, like the wetted top layer of substrate in or near spring openings, pools and spring runs. In at least two of its known locations, this species has been found in subsurface habitats, which include caves or other underground areas of the underlying water source. Barton Springs salamanders move any unknown depth into interstitial spaces, meaning empty voids between rocks, within the spring or streambed substrate that provide foraging habitat and protection from predators and drought conditions.

Barton Springs salamanders appear to be opportunistic predators of small, live invertebrates. Amphipod remains have been found in the stomachs of wild-caught salamanders. Analysis involving stable isotope techniques indicated a high a preference for planarian flatworms (Dugesia sp.). Barton Springs salamanders have been found to increase their consumption of midge fly larvae (family Chironomidae) and amphipods (Hyalella azteca) only after the near depletion of the planarian population. This type of prey switching indicates an opportunist forging strategy whereby a predator changes its diet to take advantage of temporarily available prey.

The Barton Springs salamander likely spends much of its time within the interstitial spaces of the freshwater substrates it inhabits. Studies have shown that they forage on invertebrate species opportunistically and demonstrate an innate predator recognition which allows them to differentiate between low and high-risk predator species within their habitats.

The Barton Springs salamander was first collected from Barton Springs in 1946 and formally described in 1993. Adults reach about 2.5 to 3 inches (63 to 76 mm) in total length. Adult body morphology includes reduced eyes and elongate, spindly limbs that are indicative of a semi-subterranean lifestyle. The head is relatively broad and deep in lateral view, and the snout appears somewhat truncate when viewed from above. On either side of the base of the head is a set of three feathery gills that are bright red. The tail is relatively short with a well-developed dorsal, or upper fin, and poorly developed ventral, or lower, fin.

The coloration on the salamander’s upper body varies from light to dark brown, purple, reddish brown, yellowish cream, or orange. The characteristic mottled salt-and-pepper color pattern on the upper body surface is due to brown or black melanophores, meaning cells that contain pigments called melanin, and silvery-white iridiophores, meaning cells that contain pigments called guanine, in the skin. The arrangement of these pigment cells is highly variable and can be widely dispersed in some Barton Springs salamanders and can cause them to have an overall pale appearance. In other salamanders the melanophores may be so dense that individuals have a dark brown appearance. The ventral, or underside, of the body is cream-colored and is often translucent so that some internal organs and developing eggs in females are readily visible. The upper and lower mid-lines of the tail usually exhibit some degree of orange-yellow pigmentation.

Gravid females, eggs and larvae are typically found throughout the year in the Barton Springs, which suggests that the salamander can reproduce year-round. Observations of courtship among captive pairs of Barton Springs salamanders are consistent with the tail-straddling walk which is a behavior unique to plethodontid salamanders. During courtship, the male deposits a spermatophore, or sperm packet attached to a glycoprotein base, which then becomes attached to a plant, rock or other substrate. The spermatophore is picked up by the female and stored in a specialized portion of the cloaca, known as the spermatheca. Females of some salamander species may store spermatophores for up to two and a half years before ovulation and fertilization occur. Females of some species may also store more than one spermatophore from one or different males. In most salamanders, fertilization is internal and occurs during egg-laying whereby sperm are released onto eggs as they pass through the female’s cloaca.

The longevity of the Barton Springs salamander in the wild is unknown.

Barton Springs salamanders are aquatic and neotenic, meaning they retain larval, gill-breathing morphology throughout their lives. These neotenic salamanders do not metamorphose and leave water. Instead, they live in water throughout their life cycle where they become sexually mature and eventually reproduce. Although only a few eggs have ever been found in the wild, captive Barton Springs salamanders deposit eggs onto various substrates in their environment.  Hatching occurs between 15 and 40 days after eggs have been deposited. Newly hatched larvae have a yolk sac to sustain their nutritional needs in the early days after hatching, but they begin feeding on prey items as soon as 10 or 11 days after hatching.

The Barton Springs salamander is sympatric with, meaning that it occurs in the same range as, the Austin blind salamander (Eurycea waterlooensis). Morphological characteristics that distinguish the Austin blind salamander from the Barton Springs salamander include eyespots covered by skin instead of image-forming lenses, an extended snout, fewer costal grooves and pale to dark lavender coloration.