Vol. 1 14. No. 1 . January & February 2003 POSSIBLE REPRODUCTION OF THE COMAL SPRINGS RIFFLE BEETLE, HETERELMIS COMALENSIS (COLEOPTERA: ELMIDAE), IN CAPTIVITY 1 Joe N. Fries : ABSTRACT: Endangered Comal Springs riffle beetles have been kept in captivity at the San Marcos National Fish Hatchery and Technology Center since 1996. In 2000. beetle larvae were found in an aquarium that previously had only adults. None of the larvae survived for more than 8 months. One adult beetle survived for 19 months. KEY WORDS: Heterelmis comalensis, Coleoptera. Elmidae, Texas, reproduction. The Comal Springs riffle beetle (Heterelmis comalensis Bosse. Tuff, and Brown) (Coleoptera: Elmidae) occurs in spring-runs of the Comal River (Comal Springs), New Braunfels, Comal County, Texas (Bosse el al. 1 988), and a single specimen was found in the headwaters of the San Marcos River, Hays County. Texas, in 1992 (Barr 1993). The spring ecosystems of both rivers are dependent upon flow from the Edwards Aquifer which also provides high quality water to meet an ever-increasing human demand. Heterelmis comalensis was listed as en-dangered in 1998 by the U.S. Fish and Wildlife Service (1997), primarily be-cause of threats to its habitat. Additionally, the U.S. Fish and Wildlife Service (1996) required the development of refugium populations for the listed species from the spring ecosystems of the San Marcos and Comal rivers. Since July 1996, the San Marcos National Fish Hatchery and Technology Center (NFHTC), San Marcos, Texas, has been involved in refugium activities for H. comalensis. Beetles were collected from rocks in Comal Springs during 1996-1998 and brought to the NFHTC. They were identified as Heterelmis using Merritt and Cummins (1984) and were presumed to be H. comalensis since the only other similarly-sized elmids known from Comal Springs are M. pnsillus (Arsuffi 1993: Barr 1993) and Stenelmis sp. (Bowles et al. 2000). Beetles were placed in flow-through (Edwards Aquifer water) aquaria with limestone rocks covered with algae from Comal Springs. Aquarium configuration was modified several times, changing flow pattern and rate, rock arrangement, and adding tem-perature-conditioned bio-filtered recirculated water. Although one beetle lived for 1 1 months, survival was poor and losses averaged about 24% per month. In January 2000. 43 adult H. comalensis were collected at Comal Springs among leaf litter and rocks in the springs emerging from the edge of the spring-runs. Most of the beetles were aggregated on decaying leaves from anacua (Ehretia anacua), an endemic tree, and had attached protozoans which com-monly are found on riffle beetles (Brown 1987). The beetles were placed in an acid-washed aquarium containing a mixture of flow-through water and recircu-1 Received on December 7, 2001 : Accepted on November 23. 2003 ; U.S. Fish and Wildlife Service. San Marcos National Fish Hatchery and Technology Center. 5(K) East McCarty Lane, San Marcos. TX 78666. U.S.A. E-mail: joe_fries<5 fws.gov. Mailed on April 9. 2004
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