CHILL-COMA TOLERANCE, A MAJOR CLIMATIC ADAPTATION AMONG DROSOPHILA SPECIES

Abstract.— Most drosophilid species can be classified either as temperate or tropical. Adults of species were submitted to a cold treatment (0°C) and then brought back to ambient temperature. They generally exhibited a chill coma and the time needed to recover was measured. We found in a set of 26 temperate species that recovery was rapid (average 1.8 min, range 0.15–4.9). In contrast, a long recovery time (average 56 min, range 24–120) was observed for 48 tropical species. A few species, like Drosophila melanogaster, are cosmopolitan and can proliferate under temperate and tropical climates. In 9 of 10 such species, slight genetic differences were found: a shorter recovery in temperate than in tropical populations. Comparing physiological data to phylogeny suggests that chill‐coma tolerance has been a recurrent adaptation that is selected for in cold climates but tends to disappear under a permanently warm environment. This major climatic adaptation, evidenced in drosophilids, seems to occur in other insect groups also.     

Breakdown of tussock grass in streams along a gradient of agricultural development in New Zealand

Summary 1. We measured the breakdown rate of tussock grass in 12 New Zealand streams in catchments that provided a gradient of agricultural development. We also examined the microbial and invertebrate communities associated with decomposing tussock litter.
2. Pristine streams in the study had low concentrations of dissolved inorganic nitrogen (<10  μ g L⁻¹) and dissolved reactive phosphate (<3  μ g L⁻¹), whereas streams in the most developed catchments had high concentrations of nitrate (>2500  μ g L⁻¹) and phosphate (35  μ g L⁻¹), as well as greater amounts of suspended sediment and fine sediment covering the streambed.
3. Breakdown rate and microbial respiration were significantly related across the sites, and both were positively related to concentrations of nitrate and phosphate. Fungal biomass, measured as ergosterol, was positively related to microbial respiration and was also higher at sites with higher concentrations of nutrients. Total and shredding invertebrates were most abundant at the sites with high nutrient concentrations, but abundance of shredding invertebrates was not significantly related to breakdown rate. Amphipods were the most common shredding invertebrate at most sites, but probably did not contribute greatly to high rates of breakdown in streams in agricultural catchments.
4. With the exception of one site, nutrients from agricultural development appeared to have larger positive effects on litter breakdown than negative effects from sedimentation. Litter breakdown can serve as a functional measure of ecosystem health in streams, but caution should be exercised when a stress, such as land use, can have both positive (nutrients) and negative (sedimentation) effects.     

DNA isolation from dry and fresh samples of polysaccharide-rich plants

DNA extraction is difficult in a variety of plants because of the presence of metabolites that interfere with DNA isolation procedures and downstream applications such as DNA restriction, amplification, and cloning. The chemotypic heterogeneity among species may not permit optimal DNA yield with a single protocol; thus, even closely related species may require different isolating protocols. Here we describe a modified procedure based on the hexadecyltrimethylammonium bromide (CTAB) method to isolate DNA from tissues containing high levels of polysaccharides. The procedure is applicable to both dry and fresh tissues and was tested on chickpea seeds, soybean, and wheat leaves. This method solved the problems of DNA degradation, contamination, and low yield due to binding and/or coprecipitation with starches and polysaccharides. The isolated DNA proved amenable to PCR amplification and restriction digestion.     

Studies on the host-parasite interaction and role of esterases during biting of the Indian cattle leech, Poecilobdella granulosa.

Histochemical localization of acetylcholinesterase and butyrylcholinesterase in the salivary glands has unfolded the significant fact that salivary glands are of two types, one being enzymatically negative and the other showing positive activity. Activity of these enzymes has been linked with the operation of glandular dynamics, particularly concerning the synthetic and secretory processes. The enzymes have been seen localized in the core of jaw. Contrary to it they are absent in the papillary and interpapillary zones of the jaw. Absence of esterases in the papillary and interpapillary ductules has been correlated with its possible non-involvement in the synthesis of vasodilating and anticoagulating materials. The experiments on effect of biting on host tissue give a faint indication of vascular dilation due to bite. Likewise, experiments on enzymatic state of a salivary gland after leech-bite reveal that the diminution of the reactive coverage area in the salivary glands reaches its maximum in the case of ATPase, indicating thereby its more involvement in salivary functions than those of esterases and acid phosphatase.     

Some allied dematiaceae-dictyosporae from India

Summary In this paperTetracoccosporium andDictyoarthrinium are treated.T. cupulatum, D. lilliputeum andD. microsporum are described new, apart from the typeD. sacchari. A key to the known species ofDictyoarthrinium is proposed.Tetracoccosporium, is a maiden report for India.     

Histoenzymatic pattern of adenosine triphosphatase in the different components of the alimentary canal in some common earthworms and its possible physiological significance

The present contribution incorporates an account of the distribution of adenosine triphosphatase and its functional role in various regions of the alimentary canal of Pheretima posthuma and Barogaster annandalei. The main areas, showing adenosine triphosphatase activity in P. posthuma are sub-epithelial blood vessels in pharynx, peri-oesophageal blood vessels in oesophagus, columnar epithelial cells of gizzard and in the areas outside the typhlosole and around the supra-intestinal excretory ducts. In B. annandalei the epithelial cells of gizzard show significant enzymatic localization. In addition to this, enzymatic activity has also been found in the deeply embedded blood vessels of buccal region, peri-oesophageal vasculature, sub-epithelial vasculature of typhlosole and intestine, and in the adjoining chloragogen cells. Physiological significance of the enzymatic pattern has been discussed.     

The Unusual Transmembrane Partition of the Hexameric Channel of the Hepatitis C Virus

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