Wednesday, February 08, 2017Register
 Federally Threatened and Endangered Invertebrates and Plants of the Edwards Aquifer

Comal Springs Dryopid Beetle
Stygoparnus comalensis

Comal Springs Dryopid Beetle, photo courtesy of Texas Parks and Wildlife

[Photo: Texas Parks and Wildlife]

Description: The Comal Springs dryopid beetle is an aquatic subterranean species of the Dryopidae family (long-toed water beetles). Adaptations to its subterranean habitat are evident by its translucent exoskeleton and lack of eyes. This beetle is 0.11-0.15 inches (3-4 mm) long and reddish-brown in color.

Life History: This beetle requires atmospheric oxygen for respiration. Hairs found on the beetle's underside are unwettable and can trap air which the beetle uses to breathe as it swims. Not much is known about the feeding or mating habits of this species; however, they are thought to feed on detritus scraped from rocks.

Habitat: The larvae of the Comal Springs dryopid beetle are terrestrial and live inside air pockets on the soil and debris lining the ceiling of the underground spring orifices. The adults are fully aquatic and live in the spring openings and underground streams of the Edwards Aquifer.

Distribution: Stygoparnus comalensis is found in Comal Springs (Comal County) and Fern Bank Springs (Hays County), in the Edwards Aquifer, Central Texas.

The map below depicts the critical habitat for this species, as designated by the US Fish and Wildlife Service pursuant to the Endangered Species Act.

NOTE: No warranty is given, expressed or implied, as to the accuracy, reliability, or completeness of these data. Data do no represent a legal description of the critical habitat boundary; refer to the textual description in the appropriate final rule for this species as published in the Federal Register.

Comal Springs Dryopid Beetle (Stygoparnus comalensis) Federally Designated Critical Habitat [Figure: Houston Advanced Research Center using US FWS data]

Comal Springs Dryopid Beetle (Stygoparnus comalensis) Federally Designated Critical Habitat [Figure: Houston Advanced Research Center using US FWS data]. Click on map for larger image. 

Status: The Comal Springs dryopid beetle is a state and federally listed (1997) endangered species. Water quality in the aquifer is important to the Comal Springs dryopid beetle because of its unique method of respiration. The beetle requires high levels of dissolved oxygen (DO) to breathe and water quality impairments could lower the DO levels to the point of damaging this population. Additionally, due to the fact that this beetle's larvae are terrestrial and adults are aquatic, physical disruption or separation of these habitats could damage the population. Water quantity fluctuation is not as detrimental to this species because it can retreat into the aquifer during low flow periods. At flows of less than 40 cubic feet per second (cfs) damage to this population may occur; and at flows of 20 cfs or less there is a possible legitimate risk to this population.

Resources:

Edwards Aquifer Authority, Draft Edwards Aquifer Habitat Conservation Plan

Texas A&M, Status of the Comal Springs Dryopid Beetle

Texas Parks and Wildlife, Endangered Species of the Edwards Aquifer

US Fish and Wildlife Service, Critical Habitat Final Rule

US Fish and Wildlife Service, Endangered Species Listing

Comal Springs Riffle Beetle
Heterelmis comalensis

Thumbnail image of Comal Springs Riffle Beetle, courtesy of Texas Parks and Wildlife Department

[Photo: Texas Parks and Wildlife]

Description: The Comal Springs riffle beetle is a small aquatic beetle of the family Elmidae. It is approximately .07 inches (2 mm) long and .04 inches (1 mm) wide with females larger than males. The riffle beetle has short non-functional hind wings. It is brownish-yellow to dark brown in color, and covered with fine golden hair.

Life History: The Comal Springs riffle beetle feeds on microorganisms and debris scraped from the bottom of water bodies. The Comal Springs riffle beetle breeds year-round and its life cycle includes four stages: egg, larva (multiple instars), pupa, and adult. Other beetles of this genus have been shown to take anywhere from 6 months to 3 years to complete their life cycle, with the speed of this cycle heavily dependent upon environmental temperatures.

Habitat: This beetle's habitat includes the shallow, gravelly portion of spring runs at Comal, San Marcos, and Hueco Springs at 2-10 cm in depth, occasionally deeper.

Distribution: Heterelmis comalensis can be found at Comal, Hueco, and San Marcos Springs at the headwaters of the Comal and San Marcos Rivers in Comal and Hays counties, central Texas.

The map below depicts the critical habitat for this species, as designated by the US Fish and Wildlife Service pursuant to the Endangered Species Act.

NOTE: No warranty is given, expressed or implied, as to the accuracy, reliability, or completeness of these data. Data do not represent a legal description of the critical habitat boundary; refer to the textual description in the appropriate final rule for this species as published in the Federal Register.

Federally Designated Critical Habitat for the Comal Springs Riffle Beetle (Heterelmis comalensis) [Figure: Houston Advanced Research Center using US FWS data]

Federally Designated Critical Habitat for the Comal Springs Riffle Beetle (Heterelmis comalensis) [Figure: Houston Advanced Research Center using US FWS data]. Click on map for larger image.

Status: The Comal Springs riffle beetle is a state and federally listed (1997) endangered species. There is a refugium for this species at the San Marcos National Fish Hatchery and Technology Center. The Comal Springs riffle beetle has an extremely small range, suggesting that it requires particular habitat characteristics to live. Thus, changes in the surface or groundwater quality or quantity associated with its habitat could cause extreme negative consequences for this population. Surface and groundwater quality threats associated with its habitat include constituents associated with human sewage, animal waste, agricultural chemicals and urban runoff. Because flowing water is required for respiration, optimal spring flows should be >150 cubic feet per second (cfs). The beetle begins to lose habitat at between 150 and 100 cfs and sustained low flows of 80 cfs or lower pose a possible legitimate risk to this population.

Resources:

Edwards Aquifer Authority, Draft Edwards Aquifer Habitat Conservation Plan

Texas Parks and Wildlife, Endangered Species of the Edwards Aquifer

Texas A&M, Comal Springs Riffle Beetle Status

US Fish and Wildlife Service Critical Habitat Final Rule

US Fish and Wildlife Service, Endangered Species Listing

 

Peck's Cave Amphipod
Stygobromus pecki

Thumbnail image of Pecks Cave Amphipod, courtesy of Texas Parks and Wildlife Department

[Photo: Texas Parks and Wildlife]

Description: The Peck's cave amphipod is a subterranean, aquatic crustacean of the family Crangonyctidae. The Stygobromus genus is differentiated from the other members of the family due to its lack of eyes. It also has no skin pigmentation, giving it a translucent appearance that is consistent with other cave-dwelling species. The Peck's cave amphipod can grow up to 0.4 inches (10.5 mm) long.

Life History: Not much is known of this amphipod's life history, but information about related species suggest that the Peck's cave amphipod avoids bright light and feeds on detritus. The range of this species is limited because it cannot swim upstream against a strong current. Amphipods generally have a one year long life cycle, however cave species may take longer to mature (up to 6 years).

Habitat: The Peck's cave amphipod is a mostly subterranean species, found at the bottom of underground streams in the caves of the Edwards Aquifer, where it lives among rocks, crevices, and detritus. Outside of the aquifer, at the spring openings, the Peck's cave amphipod is easy prey and can not survive. There is little known about this species; however the Stygobromus genus, in general, prefers cool, thermally constant waters.

Distribution: Stygobromus pecki has been found at Comal Springs and Hueco Springs (Comal county), in the Edwards Aquifer, central Texas.
The map below depicts the critical habitat for this species, as designated by the US Fish and Wildlife Service pursuant to the Endangered Species Act.

NOTE: No warranty is given, expressed or implied, as to the accuracy, reliability, or completeness of these data. Data do not represent a legal description of the critical habitat boundary; refer to the textual description in the appropriate final rule for this species as published in the Federal Register.

Federally Designated Critical Habitat for the Peck's Cave Amphipod (Stygobromus pecki) [Figure: Houston Advanced Research Center using USFWS data]

Federally Designated Critical Habitat for the Peck's Cave Amphipod (Stygobromus pecki) [Figure: Houston Advanced Research Center using USFWS data]. Click on map for larger image. 

Status: The Peck's cave amphipod is a state and federally listed (1997) endangered species. Groundwater quality is important to the survival of the Peck's cave amphipod because it requires high dissolved oxygen content for respiration. This species is not as sensitive to changes in groundwater or surface water quantity as other spring-dwelling species because it can retreat into the aquifer under low flow conditions. The spring flow defined as "take" for this species is 40 cubic feet per second (cfs) or less. At 20 cfs or less there is a possible legitimate risk to the population.

Resources:

Edwards Aquifer Authority, Draft Edwards Aquifer Habitat Conservation Plan

US Fish and Wildlife Service, Endangered Species Listing

Texas A&M, Peck's Cave Amphipod Status

Texas Parks and Wildlife, Endangered Species of the Edwards Aquifer

 

Texas Wild-rice
Zizania texana

Thumbnail image of Texas Wild-rice, courtesy of Sue Emery, United States Fish and Wildlife Service

[Photo: Sue Emery, US Fish and Wildlife Service]

Description: Texas wild-rice is an aquatic, perennial grass, similar in appearance to Northern and Southern wild-rice. Texas wild-rice is 3.2-6.5 feet (1-2 m) long and usually immersed and lying flat in swift, flowing water. In slow water, the plant is more emergent. Leaves are elongate, linear, and green, ranging from 4.8-44 inches (12-110 cm) long and 0.2-1 inch (0.5-2.5 cm) wide. This plant flowers in spring and fall, although it may occur throughout the year in warm weather. Seeds are cylindrical, black, brown, or green in color, and 4.3-7.6 mm long by 1-1.5 mm wide.

Life History: Texas wild-rice occurs in the upper portion of the San Marcos River with pondweed, wild celery, arrowhead, hydrilla, hornwort, elodea, and water primrose. Texas wild-rice reproduces both sexually and asexually via seeds or stolons. Currently its primary means of reproduction is asexual because of inhiition of sexual reproduction due to unsuitable environmental conditions. Texas wild-rice is wind pollinated.

Habitat: Texas wild-rice prefers to grow in the swift currents of the spring-fed San Marcos River, away from the banks in shallow water (3.2 feet [1 m] or less). It forms large clumps that are rooted in limestone, sand, or gravel. It prefers a coarse sand substrate with low organic matter. Texas wild-rice is associated with other native species.

Distribution: Zizania texana is found in the upper two miles of the San Marcos River, from just below Spring Lake down to the Interstate 35 bridge, Hays County, TX.

The map below depicts the critical habitat for this species, as designated by the US Fish and Wildlife Service pursuant to the Endangered Species Act.

NOTE: No warranty is given, expressed or implied, as to the accuracy, reliability, or completeness of these data. Data do no represent a legal description of the critical habitat boundary; refer to the textual description in the appropriate final rule for this species as published in the Federal Register.

Federally Designated Critical Habitat for Texas Wild-rice (Zizania texana) [Figure: Houston Advanced Research Center using US FWS data]

Federally Designated Critical Habitat for Texas Wild-rice (Zizania texana) [Figure: Houston Advanced Research Center using US FWS data]. Click on map for larger image. 

Status: Texas wild-rice is a state and federally listed (1978) endangered species. There is a refugium for this species at the San Marcos National Fish Hatchery and Technology Center. Dam construction and urban development around the San Marcos River have caused changes in the turbidity, sedimentation, and depth of the river. In addition, growth of invasive species and drawdown of the spring have caused slower current velocities in the San Marcos. The US Fish and Wildlife Service defined the flow required for take as 100 cubic feet per second or less. These habitat changes constitute a serious threat to the one remaining population of Texas wild-rice. Other concerns are herbivory by nutria and waterfowl, as well as impacts of recreationists, (i.e. tubers and swimmers).

Resources:

Poole, Jackie and Bowles, David E. 1999. Habitat characterization of Texas Wild-rice (Zizania texana Hitchcock), an endangered aquatic macrophyte from the San Marcos River, TX, USA. Aquatic Conservation: Marine Freshwater Ecosystems. Vol. 9, pp 291-302.

Power, Paula. 1997. Moisture, Seeds, and Reproductive Failure in Texas Wildrice (Zizania texana). The Southwestern Naturalist. Vol. 42, No. 4, pp. 435-440.

Texas Parks and Wildlife, Endangered Species Profile

US Fish and Wildlife Service, San Marcos Recovery Plan


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