Observations, Communicated to the Publisher by Mr. Antony van Leewenhoeck, in a Dutch Letter of the 9th of Octob. 1676. Here English'd: concerning Little Animals by Him Observed in Rain-Well-Sea. and Snow Water; as Also in Water Wherein Pepper Had Lain Infused

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Rates of nucleotide substitution in sexual and anciently asexual rotifers

The class Bdelloidea of the phylum Rotifera is the largest well studied eukaryotic taxon in which males and meiosis are unknown, and the only one for which these indications of ancient asexuality are supported by cytological and molecular genetic evidence. We estimated the rates of synonymous and nonsynonymous substitutions in the hsp82 heat shock gene in bdelloids and in facultatively sexual rotifers of the class Monogononta, employing distance based and maximum likelihood methods. Relative-rate tests, using acanthocephalan rotifers as an outgroup, showed slightly higher rates of nonsynonymous substitution and slightly lower rates of synonymous substitution in bdelloids as compared with monogononts. The opposite trend, however, was seen in intraclass pairwise comparisons. If, as it seems, bdelloids have evolved asexually, an equality of bdelloid and monogonont substitution rates would suggest that the maintenance of sexual reproduction in monogononts is not attributable to an effect of sexual reproduction in limiting the load of deleterious nucleotide substitutions

Microbial Life in Supraglacial Environments

Supraglacial environments occupy 11% of Earth’s surface area and represent a critical interface between climate and ice. This century has brought a renewed appreciation that glacier surfaces represent a collective of diverse microbial niches which occur wherever sufficient liquid water is available to support microbial activity: even at the microscopic scales of ice crystal boundaries within the crystalline matrices of snow or glacial ice. Within this chapter, we review the range of microbial habitats associated with snowpacks, the glacial ice photic zone, and phototrophic microbial biofilms formed by supraglacial algae or by the darkening of microbe–mineral aggregates known as cryoconite. In summary, glacier surfaces are home to surprisingly biodiverse and active microbial communities despite their low temperatures and austere conditions. Consequently, microbial communities and their processes are interposed between climate and ice and merit urgent consideration in the light of the effects of climate warming on Earth’s supraglacial environments