The Uptake and Utilization of Bacteria, Amino Acids and Carbohydrate by the Rumen Ciliate Entodinium longinucleatum in Relation to the Sources of Amino Acids for Protein Synthesis

Entodinium longinucleatum grown in vitro in the presence of bacteria engulfed a wide range of bacterial species at rates of 130–3400 bacteria/h/protozoon (from suspensions of 10 bacteria/ml), but showed a preference for Klebsiella aerogenes and Proteus mirabilis which occurred in the growth medium. Some of the bacteria were digested with release of soluble material into the medium. Free amino acids were incorporated by the protozoa in the presence of chloramphenicol at rates of 5·4–15·1 nmol/h/10⁶ protozoa and approximately 40% of the amino acid-carbon was incorporated into protein. There was no appreciable synthesis of protozoal protein from carbohydrate. Evidence was obtained that the protozoa obtained the amino acids required for growth largely from engulfed bacteria.     

THE EFFECT OF INFECTION WITH TOBACCO ETCH VIRUS ON THE RATES OF RESPIRATION AND PHOTOSYNTHESIS OF TOBACCO LEAVES

Unlike tobacco mosaic virus, which increases the respiration of tobacco leaves within an hour of their being inoculated, a virulent strain of tobacco etch virus did not change respiration rates until leaves showed external symptoms. The respiration rates of inoculated or systemically infected leaves with symptoms rose to 40% above that of healthy leaves, three times the increase produced by tobacco mosaic virus. The increased respiration rate occurred at all times of the year and was maintained through the life of the leaves.
Leaves infected with tobacco etch virus and showing symptoms had a photo-synthetic rate 20% lower than that of healthy leaves.     

An ophiuroid trackway from the Lower Devonian Hunsrück Slate, Germany

A new trace fossil, Arcichnus saltatus , from the Lower Devonian Hunsrück Slate, Germany, is interpreted as the trackway of a protasterid ophiuroid, Taeniaster. The trackway consists of a series of horseshoe-shaped impressions, produced by a pair of arms, a feature characteristic of some ophiuroid trackways. This new trace fossil demonstrates that protasterids lived both infaunally and epifaunally.     

The butterfly Danaus chrysippus (L.) in East Africa: polymorphism and morph-ratio clines within a complex, extensive and dynamic hybrid zone

Samples of the polymorphic butterfly Danaus chrysippus are analysed from six well separated sites in East Africa. Morph-ratio clines are described for four diallelic genes A, B, C and L, each of which influences the visual phenotype. Each of the four clines has a different orientation, consistent with an hypothesis that the polymorphism originated from hybridization between a number of polytypic denies which have at various times undergone range expansion. Allopatric subspeciation in isolated Pleistocene refugia is postulated. The phenotype of each geographical race is shared with one of the morphs within the hybrid zone; other sympatrically maintained polymorphic forms are normally confined to the hybrid zone. Wright's isolation-by-distance model best explains the present distribution of gene frequencies. Morph-ratios differ significantly between the sexes and are sometimes associated with heterozygote excess; gametic and genotypic disequilibria are general throughout the region and suggest the clines are maintained by strong natural selection. Seasonal cycling of phenotype frequency is believed to result from extensive migratory movements rather than natural selection. Female-biased sex-ratio, which is also seasonal, and Haldanc rule effects, result from hybrid breakdown when genetically distinct demes meet and interbreed. Oscillating sex-ratios and frequency of colour genes are functionally linked by negative feedback. The polymorphism owes its origin to allopatrie evolution but is now maintained sympatrically.     

Spot variation in Maniola jurtina (L.) (Lepidoptera: Satyridae) in southern Portugal and a comparison with the Canary Islands

A sample of 2013 meadow brown butterflies, Maniola jurtina , was obtained in the Algarve, southern Portugal, on behalf of E.B. Ford, the founder of ecological genetics. Variation in the meadow brown occupied Ford's attention for more than 40 years. Ford died in 1988; most of his collection had earlier been destroyed, but the meadow browns remained and became available for analysis. The butterflies were scored for spotting characters on both fore- and hindwings. The population is homogeneous over the entire area of the Algarve and there is no conclusive evidence of a difference between the two years of collection (1986 and 1987). It is probably also homogeneous with southern Iberia in general, an area unique in the western Palaearctic range of the species as it is characterized by a high spot average in males and a low spot average in females. Algarve butterflies differ markedly from those of the Canary Islands, where there is considerable inter-island heterogeneity, supporting the view that the Canary Island populations did not originate from southern Iberia. In the Algarve, many females aestivate and by September there is an essentially all-female population. These are low-spotted and differ significantly from females active in May and June at the start of the annual (one generation) flight season.     

Evaluation of three procedures using a laser densitometer and microcomputer for estimating molecular sizes of restriction endonuclease digest fragments and application to Campylobacter jejuni chromosomal DNA

Laser densitometer scanning and three methods of computation were investigated for estimating sizes of restriction endonuclease digest fragments of Campylobacter jejuni chromosomal DNA. Accuracy of the procedures was determined with standard bacteriophage lambda DNA fragments. The program DNASIZE was the most accurate for fragments between 2.3 and 33.5 kb while the program DNAFRAG and multiple regression analysis gave slightly greater errors particularly for smaller fragments. Hae III fingerprints of DNA from six C. jejuni strains contained at least 25 resolvable fragments with sizes between 3.2 and 35.8 kb estimated by DNASIZE and several differences between pattern types were detected.