Post-Meiotic Intra-Testicular Sperm Senescence in a Wild Vertebrate

There is growing interest in sperm senescence, both in its underlying mechanisms and evolutionary consequences, because it can impact the evolution of numerous life history traits. Previous studies have documented various types of sperm senescence, but evidence of post-meiotic intra-testicular sperm senescence in wild animals is lacking. To assess such senescence, we studied within-season changes in sperm motility in the common toad (Bufo bufo), where males produce all sperm prior to the breeding season. We found that males exposed to experimentally induced re-hibernation at the start of the breeding season, that is to experimentally lowered metabolic rates, stored sperm of significantly higher motility than males that were kept under seminatural conditions without females throughout the breeding season. This finding indicates that re-hibernation slows normal rates of sperm ageing and constitutes the first evidence to our knowledge of post-meiotic intra-testicular sperm senescence in a wild vertebrate. We also found that in males kept in seminatural conditions, sperm motility was positively related to the number of matings a male achieved. Thus, our results suggest that post-meiotic intratesticular sperm senescence does not have a genetically fixed rate and may be modulated by temperature and possibly by mating opportunities

Bayesian Analysis of Inflation III: Slow Roll Reconstruction Using Model Selection

We implement Slow Roll Reconstruction -- an optimal solution to the inverse problem for inflationary cosmology -- within ModeCode, a publicly available solver for the inflationary dynamics. We obtain up-to-date constraints on the reconstructed inflationary potential, derived from the WMAP 7-year dataset and South Pole Telescope observations, combined with large scale structure data derived from SDSS Data Release 7. Using ModeCode in conjunction with the MultiNest sampler, we compute Bayesian evidence for the reconstructed potential at each order in the truncated slow roll hierarchy. We find that the data are well-described by the first two slow roll parameters, \epsilon and \eta, and that there is no need to include a nontrivial \xi parameter.Comment: 14 pages, 12 figures, minor changes; final version; accepted in PR

FISHES OF THE NIOBRARA RIVER AT AGATE FOSSIL BEDS NATONAL MONUMENT 2011 SURVEY

In June 2011, a fish inventory was conducted in the Niobrara River at Agate Fossil Beds National Monument (AGFO). Collecting techniques and locations were similar to those used in previous surveys conducted in 1979 and 1989. Results of the 2011 survey indicated a major change in the fish community had occurred during this time period. Although absent in the 1979 and 1989 surveys, Northern pike (Esox lucius) were the dominant fish species at AGFO in 2011. White sucker (Catostomus commersoni) was the single remaining species from the fish community identified in the 1979 and 1989 inventories, and another new species, Green sunfish (Lepomis cyanellus) was added. Except for the addition of the sunfish, these findings basically confirmed the results of an electrofishing inventory conducted in 2008. Compared to the 1979‐1989 surveys, the number of fish species decreased from 9 to 3 in 2011, and the total numbers of individual specimens declined from over 600 to fewer than 70. Additional fish collections in 2011 at the Nature Conservancy’s Cherry Ranch upstream from the monument indicated that a basically intact fish community comprised of 10 species still exists in good numbers. This is west of a control structure on the Nunn property that presumably restricts the upstream migration of pike

Radio Variability of Radio Quiet and Radio Loud Quasars

The majority of quasars are weak in their radio emission, with flux densities comparable to those in the optical, and energies far lower. A small fraction, about 10%, are hundreds to thousands of times stronger in the radio. Conventional wisdom holds that there are two classes of quasars, the radio quiets and radio louds, with a deficit of sources having intermediate power. Are there really two separate populations, and if so, is the physics of the radio emission fundamentally different between them? This paper addresses the second question, through a study of radio variability across the full range of radio power, from quiet to loud. The basic findings are that the root mean square amplitude of variability is independent of radio luminosity or radio-to-optical flux density ratio, and that fractionally large variations can occur on timescales of months or less in both radio quiet and radio loud quasars. Combining this with similarities in other indicators, such as radio spectral index and the presence of VLBI-scale components, leads to the suggestion that the physics of radio emission in the inner regions of all quasars is essentially the same, involving a compact, partially opaque core together with a beamed jet.Comment: 32 pages, 9 figures. Astrophysical Journal, in pres