A survey is made of the overall pattern of distribution of freshwater fish within Malaya and also of the associations found in the three important habitat types. The lack of east-west differentiation indicates that geographical barriers are not important in determining the distributional pattern. A marked north-south differentiation probably reflects edaphic and climatic factors. Analyses based on constancy are given for the fish associations of blackwaters, ordinary streams in tree country, and riceland habitats. Each has a distinctive fish association with a relatively small number of frequent species. Blackwater associations can be divided into subassociations corresponding to different types of blackwaters. Tree country and riceland associations show some regional differentiation. The tree country association is remarkably diversified and appears to be a true association, not a fortuitous assemblage of species with similar tolerances. Adverse factors such as low oxygen and low pH probably restrict the associations found in blackwaters and ricelands. These contain both specialist and generally tolerant species, the latter becoming more important the more extreme the habitat. The riceland fauna is depauperate as compared with neighboring countries, and there are possibly vacant ecological niches.
The yellow fever mosquito Aedes aegypti has developed resistance to DDT in the Caribbean region and in South-East Asia, but not in West Africa. Therefore West African strains were compared with South-East Asian strains for their response to laboratory selection with DDT. It was found that West African strains were much slower to respond initially, but eventually could build up a high degree of DDT-resistance. By crossing and backcrossing with a susceptible marker-gene strain, it was found that this resistance was due to a single gene linked with the gene y (yellow) on chromosome 2 at a cross-over distance of approximately 35 units in an Upper Volta strain as in a Bangkok strain; interstrain crosses indicated that the gene was the same as that in a Trinidad strain and in one from Penang. Dieldrin-resistance could be readily induced in the Upper Volta strain and proved to be due to a gene also linked with y but at a crossover distance of approximately 25 units, comparable to that in Caribbean strains previously studied. Material from Karachi, West Pakistan, developed a dieldrin-resistance also showing 25% crossing over with y, and a DDT-resistance also linked with this chromosome-2 marker gene.
1. A skin lesion was made in rats by dorsal incision and the insertion of a polythene tube. 2. Over a period of 25 days after wounding, assays were performed for ascorbic acid, DNA, hydroxyproline, methionine, tryptophan, tyrosine and free amino acids in the lesion tissue. 3. The neutral-salt-soluble proteins of the lesion tissue were fractionated on DEAE-Sephadex, with the separation of fibrinogen and gamma-globulin from a serum protein fraction. 4. Over a period of 20 days after wounding, in wounded rats and in controls, assays were conducted for: ascorbic acid in lens and liver, hydroxyproline, soluble protein, methionine and water in muscle and tendon, and free amino acids in muscle. 5. Relative to controls there was a decrease in lens and liver ascorbic acid, a rise in tendon hydroxyproline, a rise in muscle free amino acids, a fall in muscle protein and a rise in tendon and muscle water.