directed at attracting the guarding male. Mating pairs come together, swimming, swirling and waving their bodies simultaneously as the female releases single eggs which are immediately fertilized by the male. The eggs adhere to roots, aquatic vegetation, rocks, travertine or sunken objects and are abandoned to their fate. The Julimes pupfish is considered to be the freshwater teleost that lives in the highest-temperature waters on the planet and is possibly also the vertebrate with the smallest known distribution range. Genetics Effective population size was evaluated in 2013 and found to be critically low, indicating that "this pupfish is at genetic risk of extinction through loss of adaptive variance and, potentially, from inbreeding depression." Mitochondrial variation was also extremely low, and haplotype frequency was biased heavily in favor of one of two variants. The most common variant represented a divergent lineage exclusive to this pupfish; which supports recognition of Julimes pupfish as a valid and critically endangered species. Additionally, twenty-five microsatellite loci for the Julimes pupfish were screened across 19 individuals. The number of alleles per locus ranged from 2 to 14, observed heterozygosity ranged from 0.105 to 0.947, and the probability of identity values ranged from 0.022 to 0.588. Tests for deviations from Hardy–Weinberg equilibrium (HWE) and for genotypic disequilibrium were conducted using GENEPOP v4.0 (Rousset 2008). After sequential Bonferroni correction for multiple comparisons, significant deviation from HWE expectations was observed at five loci. all locus-pairs conformed to expectations of genotypic equilibrium. In accordance with conservation agreements between Pronatura Noreste A. C. and Amigos del Pandeño, A.C. test results are being used for long-term genetic monitoring under the ‘‘Vital Signs’’ program for the geothermal Julimes springs. Habitat Within the hot spring, aquatic vegetation includes a single patch of cattail (Typha latifolia). Cyanobacteria mats predominate throughout the system, showing different species composition and forming mosaics of different colors, textures and growth types. Colors range from light green-blue to brownish-red. Faunal associates include a mix of endemic species in the following taxa: an undescribed poeciliid fish (Gambusia sp.) inhabiting the cooler sections of the system, the recently described cochliopid springsnail (Tryonia julimensis); and IUCN (CR) red listed sphaeromatid isopod (Thermosphaeroma macrura). In January 2013, Amigos del Pandeño restored ~300 square meters of dried lower marsh habitat with support from Pronatura Noreste. The restored area, which more than doubled pupfish suitable habitat within the system was soon colonized by both pupfish and Gambusia