Devils Hole Pupfish Cyprinodon Diabolis Research Articles

Enhancing Hatch Rate and Survival in Laboratory‐Reared Hybrid Devils Hole Pupfish through Application of Antibiotics to Eggs and Larvae

AbstractWe evaluated the effectiveness of four antibiotics in enhancing the hatch rate, larval survival, and adult survival of hybrid Devils Hole Pupfish Cyprinodon diabolis (hybridized with Ash Meadows Amargosa Pupfish C. nevadensis mionectes). Cephalexin (CEX; concentration = 6.6 mg/L of water), chloramphenicol (CAM; 50 mg/L), erythromycin (ERY; 12.5 mg/L), and trimethoprim sulfamethoxazole (TMP‐SMX; 25 mg/L) were applied as a constant bath either to incubating eggs or to larvae that hatched from untreated eggs. Hatch rate was roughly doubled by incubation in the presence of CAM (68% hatch) and TMP‐SMX (66%) relative to the control (28%). Cephalexin and ERY conferred no benefit upon the hatch rate. Among fry that hatched from treated eggs, there was no increase in 15‐d larval survival. However, fish that hatched from eggs treated with CAM, ERY, and TMP‐SMX demonstrated enhanced survival at 360 d (51.2, 38.4, and 43.6%, respectively) and at 540 d (22.6, 6.8, and 20.2%, respectively); the untreated control had no survivors to those time points. All groups of eggs treated with antibiotics showed reductions in bacterial colony‐forming units (CFUs) at 24 h posttreatment. At 120 h posttreatment, CEX‐treated eggs had CFU counts similar to those of the control, whereas the TMP‐SMX‐treated eggs had the lowest CFU counts. Eggs treated with CAM and ERY had similar CFU counts, which were significantly reduced from the control counts. Larvae that were treated with CAM and TMP‐SMX within 12 h posthatch showed enhanced 15‐d survival (74% and 72%, respectively) in comparison with the control (56%). For pupfish rearing efforts in which antibiotic use is appropriate, CAM and TMP‐SMX appear to provide the greatest benefit, particularly when applied to incubating eggs rather than to hatched larvae.

Diabolical survival in Death Valley: recent pupfish colonization, gene flow and genetic assimilation in the smallest species range on earth.

One of the most endangered vertebrates, the Devils Hole pupfish Cyprinodon diabolis, survives in a nearly impossible environment: a narrow subterranean fissure in the hottest desert on earth, Death Valley. This species became a conservation icon after a landmark 1976 US Supreme Court case affirming federal groundwater rights to its unique habitat. However, one outstanding question about this species remains unresolved: how long has diabolis persisted in this hellish environment? We used next-generation sequencing of over 13 000 loci to infer the demographic history of pupfishes in Death Valley. Instead of relicts isolated 2-3 Myr ago throughout repeated flooding of the entire region by inland seas as currently believed, we present evidence for frequent gene flow among Death Valley pupfish species and divergence after the most recent flooding 13 kyr ago. We estimate that Devils Hole was colonized by pupfish between 105 and 830 years ago, followed by genetic assimilation of pelvic fin loss and recent gene flow into neighbouring spring systems. Our results provide a new perspective on an iconic endangered species using the latest population genomic methods and support an emerging consensus that timescales for speciation are overestimated in many groups of rapidly evolving species.

Underwater Videography Outperforms Above‐Water Videography and In‐Person Surveys for Monitoring the Spawning of Devils Hole Pupfish

AbstractThe monitoring of threatened and endangered fishes in remote environments continues to challenge fisheries biologists. The endangered Devils Hole Pupfish Cyprinodon diabolis, which is confined to a single warm spring in Death Valley National Park, California–Nevada, has recently experienced record declines, spurring renewed conservation and recovery efforts. In February–December 2010, we investigated the timing and frequency of spawning in the species' native habitat by using three survey methods: underwater videography, above‐water videography, and in‐person surveys. Videography methods incorporated fixed‐position, solar‐powered cameras to record continuous footage of a shallow rock shelf that Devils Hole Pupfish use for spawning. In‐person surveys were conducted from a platform placed above the water's surface. The underwater camera recorded more overall spawning throughout the year (mean ± SE = 0.35 ± 0.06 events/sample) than the above‐water camera (0.11 ± 0.03 events/sample). Underwater videography also recorded more peak‐season spawning (March: 0.83 ± 0.18 events/sample; April: 2.39 ± 0.47 events/sample) than above‐water videography (March: 0.21 ± 0.10 events/sample; April: 0.9 ± 0.32 events/sample). Although the overall number of spawning events per sample did not differ significantly between underwater videography and in‐person surveys, underwater videography provided a larger data set with much less variability than data from in‐person surveys. Fixed videography was more cost efficient than in‐person surveys ($1.31 versus $605 per collected data‐hour), and underwater videography provided more usable data than above‐water videography. Furthermore, video data collection was possible even under adverse conditions, such as the extreme temperatures of the region, and could be maintained successfully with few study site visits. Our results suggest that self‐contained underwater cameras can be efficient tools for monitoring remote and sensitive aquatic ecosystems.Received April 17, 2015; accepted September 10, 2015

Propagation of Hybrid Devils Hole Pupfish × Ash Meadows Amargosa Pupfish

AbstractRecent censuses of Devils Hole Pupfish Cyprinodon diabolis revealed that fewer than 100 individuals currently remain in the wild. Captive propagation is among actions being considered to prevent their extinction, but no pure‐strain Devils Hole Pupfish were available for broodstock. To help provide emergency information, we investigated techniques to propagate their most closely related relative, hybrid Devils Hole Pupfish C. diabolis × Ash Meadows Amargosa Pupfish C. nevadensis mionectes. We tested various temperatures and larval feeds with respect to egg production, larval survival, and growth. Larval survival and growth were similar from 24°C to 32°C and egg production peaked at static 28°C; however, reducing water temperatures to 23°C and then raising them to 28°C resulted in even higher production. Larvae fed infusoria, Rio Grande Silvery Minnow Chow (RGSM), or Zeigler larval diet (ZLD) had the highest survival (79.4, 71.6, and 73.4%, respectively), and those fed Otohime (OTO) had the lowest survival (60.8%), although OTO provided greatest (14 mm) 30‐d growth. Supplementation of RGSM or ZLD with Artemia nauplii increased growth but decreased survival. Larval production was maximized by placing six spawning mops, constructed of yarn and tile, in each of four 437‐L parental aquaria, stocked with 24 adult fish each (1:1 sex ratio) for 3 d, to attract adults and provide spawning substrate. A 30% water change conducted on the same day of mop placement lowered water temperature from 28°C to 23°C. Water temperature was raised back to 28°C over 48 h. After 3 d, mops were transferred to hatching aquaria that were held at 28°C and aerated until larval hatch. Although some differences likely exist in effective propagation techniques for hybrid and pure‐strain Devils Hole Pupfish, these data help provide initial recommendations to aid recovery.

Ecological Comparison between Three Artificial Refuges and the Natural Habitat for Devils Hole Pupfish

Abstract Attempts to maintain refuge populations of Devils Hole pupfish Cyprinodon diabolis in artificial tanks have achieved limited success. Previous studies have documented changes in morphological, behavioral, and genetic characteristics of refuge populations, which suggest that environmental conditions (and thus selective pressures) differ from those found in Devils Hole (DH). Physical, chemical, and biological characteristics were compared among the three Devils Hole pupfish refuges (Hoover Dam, School Springs, and Point of Rocks) and between each refuge and DH. In contrast to the thermally constant environment in DH (∼33°C), mean refuge temperatures were cooler and fluctuated on a weekly and seasonal basis. On two occasions, extreme temperature fluctuations lasting several weeks (due to water supply malfunctions) were recorded at the Hoover Dam (6°C decrease) and School Springs (22°C decrease) refuges. The physical design of the refuges precludes surface runoff from entering them; thick layers of a...