Comparative study of diatoms and macroinvertebrates as indicators of severe water pollution: Case study of the Kebena and Akaki rivers in Addis Ababa,Ethiopia

We assessed the relative performance of diatoms and macroinvertebrates to measure municipal and industrial impacts on the ecological integrity of the three major rivers flowing through Addis Ababa. Both community metric and multivariate statistical techniques were used to analyze the environmental variables and species data along the pollution gradient. This study in the Addis Ababa urban area revealed that three biologically highly stressed rivers are being impacted primarily by physical habitat degradation and both point and nonpoint pollution. The macroinvertebrate composition was liable to severe physical habitat and chemical water quality degradation. Consequently, macroinvertebrates were less diverse and not found at all at the most polluted sites with very low dissolved oxygen levels. Based on community metrics and multivariate analysis results, diatoms more reliably indicated a gradient of pollution than macroinvertebrates. However, both organism groups equally discriminated the two relatively unimpacted upstream sites from all other impacted sites. As diatoms are immobile and ubiquitous (i.e., at least a few can be found under almost any condition), they are good indicators of pollution levels among heavily impacted sites where macroinvertebrates are completely absent or less diverse. Therefore, diatoms are the powerful bioindicators for monitoring urban-impacted and seriously stressed rivers and to examine pollution gradients and impacts of specific pollution sources.     

Evidence for deoxyribonucleotide sequence divergence between staphylococci living on human and other primate skin

Human and nonhuman primate strains ofStaphylococcus haemolyticus andS. warneri were examined for relatedness to each other and other members of the genusStaphylococcus by using DNA-DNA hybridization techniques. The results indicate that human and nonhuman primate strains have diverged and are members of separate DNA homology groups or subspecies inS. haemolyticus and inS. warneri. There is partial evidence that members of the primateS. epidermidis species group are more closely related to one another than to other species. The preliminary data presented in this report are in agreement with the hypothesis that at least certain staphylococci have evolved concurrently with their hosts (conjugate evolution).     

Deoxyribonucleotide sequence divergence betweenStaphylococcus cohnii subspecies populations living on primate skin

Staphylococcus cohnii strains isolated from various primates could be separated into three distinct groups or subspecies on the basis of phenotypic characterization and DNA-DNA hybridization techniques. These included a human-specificS. cohnii subspecies (denoted here as subsp. 1), a widely distributed primateS. cohnii subspecies (subsp. 2), and a Ceboidea (New World monkey)-specificS. cohnii subspecies (subsp. 3). Divergence of the latter subspecies from the other two is great enough to place it in a near (separate)-species status.S. cohnii represents the third example of aStaphylococcus species where DNA divergence has been demonstrated between human and nonhuman primate-adapted populations. The data presented in this report continue to support the hypothesis that at least certain staphylococci have evolved together with their hosts by conjugate evolution.Paper No. 8555 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, N.C. 27650     

Staphylococcus capitis subsp. ureolyticus subsp. nov. from human skin

A new subspecies, Staphylococcus capitis subsp. ureolyticus, was isolated from human skin and is described on the basis of studies of 15 to 26 strains. DNA-DNA reassociation reactions demonstrated that these strains were closely related to Staphylococcus capitis but were significantly divergent. The strains of S. capitis subsp. ureolyticus can be distinguished from S. capitis by their positive urease activity, their ability to produce acid from maltose under aerobic conditions, their fatty acid profile, and their colony morphology. The type strain of the new subspecies is strain ATCC 49326.     

Size and mortality rates of Glossina pallidipes in the semi-arid zone of southwestern Kenya

Seasonal changes in the mean size of tsetse, Glossina pallidipes Austen, as indicated by wing vein length, were monitored during 1983-86 at Nguruman, southwestern Kenya. Changes in size of nulliparous females and wing fray category 1 males were shown to be correlated with the relative humidity 2 months before they were captured. Soil temperature when flies were in the pupal stage had much less effect. Size dependent mortality was demonstrated, with the mean size of flies emerging from pupae significantly less than that of field-caught flies. This mortality must occur at emergence, since there was no evidence of size-dependent mortality once the flies became available to the trap. Size was correlated with density-independent mortality acting on the parent population 2 months previously. It might therefore be possible to use size as an index of the intensity of such mortality. This could be useful when assessing the level of additional mortality required to suppress tsetse populations.     

Nuclear DNA sequences from late Pleistocene megafauna

We report the retrieval and characterization of multi- and single-copy nuclear DNA sequences from Alaskan and Siberian mammoths (Mammuthus primigenius). In addition, a nuclear copy of a mitochondrial gene was recovered. Furthermore, a 13,000-year-old ground sloth and a 33,000- year-old cave bear yielded multicopy nuclear DNA sequences. Thus, multicopy and single-copy genes can be analyzed from Pleistocene faunal remains. The results also show that under some circumstances, nucleotide sequence differences between alleles found within one individual can be distinguished from DNA sequence variation caused by postmortem DNA damage. The nuclear sequences retrieved from the mammoths suggest that mammoths were more similar to Asian elephants than to African elephants.