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most eggs from earlier spawnings, over a gravel substrate, were eaten by the <br />adults. Eggs from later spawnings were saved from predation by lining the <br />bottom of the tanks with the artificial plastic substrate, through which the <br />eggs would sink beyond the reach of the adults. Young were produced from <br />spawnings of four separate groups of two females and three males each which <br />spawned between 30 August and 9 September 1988, one group at 18 and three at <br />24 C. Temperature for one batch of eggs spawned at 24 C was increased to <br />28 C. Fry are thus presently being raised that have been incubated, hatched, <br />and reared at 18, 24, and 28 C.' The young speckled dace will be maintained <br />at these three temperatures until they are large enough for morphologic <br />measurements. This could determine the extent to which meristic features of <br />R. osculus varrowi are affected by temperature during development, and <br />whether specimens developing at a level (28 C) similar to those experienced <br />by .- o_ thermalis will remain differentiable from the latter. <br />Despite the relative ease with which we have been able to induce <br />spawning in speckled dace, we have not yet been able to do so with Kendall <br />Warm Springs dace. Various combinations of conditions in the spawning <br />tanks, including flowing vs. static water, different substrates, and <br />presence or absence of vegetation, have not yet produced results. <br />Summary <br />Results to date provide new evidence in support of the differentiation <br />of Kendall Warm Springs dace, R. o_, thermalis, from speckled dace of the <br />upper Green River drainage, R. o_ varrowi. The most important differences <br />have come from pharyngeal tooth counts and mitochondrial DNA analyses, <br />neither of which have been compared previously in these fish. Mitochondria) <br />DNA analyses are continuing with additional specimens. Further morphologic <br />comparisons will be conducted on young speckled dace presently being reared <br />at 18, 24, and 28 C, the latter similar to temperatures within Kendall Warm <br />Springs. If results of these ongoing investigations continue to show <br />differences between Kendall Warm Springs dace and speckled dace, this would <br />provide important evidence to support the original description of R. o_ <br />thermalis by Hubbs and Kuhne (1937) as an identifiable variant of R_ <br />osculus. <br />Literature Cited <br />Avise, J. C.,, E. Bermingham, L. G. Kessler, and N. C. Saunders. <br />1984. Characterization of mitochondrial DNA variability in a hybrid swarm <br />between subspecies of bluegill sunfish (Lepomis macrochirus). Evolution, <br />38:931-941. <br />Brussard, P. F., M. C. Hall, and J. Wright. 1981. Structure and <br />affinities of freshwater sea lamprey (Petromvzon marinus) populations. <br />Can. J. Fish. Aquat. Sci., 38:1708-1714. <br />Hubbs, C. L. and E. R. Kuhne. 1937. A new fish of the genus Apocope <br />from a Wyoming warm spring. Occ. Papers, Museum Zoo]. Univ. Michigan, <br />343:1-21. <br />Paladino, F. V., J. R. Spotila, J. P. Schubauer, and K. T. Kowalski. <br />1980. The critical thermal maxima: a technique used to elucidate <br />physiological stress and adaptation in fishes. Rev. Can. Biol., 39:115-122. <br />10