Isoenzymes of snail livers. I. Hydrolysing enzymes and peroxidase

Genetic structure and parasite compatibility of Bulinus globosus (Gastropoda: Planorbidae) from two areas of different endemicity of Schistosoma haematobium in Zimbabwe

A comparative study of the genetic structure of 8 populations of B.globosus from 2 areas of different endemicity of Schistosoma haematobium was done. Five populations were from Chiweshe (high endemicity) and three were from Plumtree (low endemicity). Genetic structure, as determined by allozyme genetics, revealed high levels of genetic variability in Chiweshe populations (Ho = 0.12-0.26) and low levels in Plumtree (Ho = 0.06-0.12). Populations from Chiweshe were genetically heterogeneous whereas in Plumtree the populations were uniform. There were significant deviations from Hardy-Weinberg proportions at different loci in Chiweshe populations. The observed excess of homozygotes was probably caused by partial selfing. The compatibility studies showed variation between allopatric and sympatric combinations of snails and parasites, and the Plumtree parasite had a significant influence on the compatibility parameters. This strain had a positive correlation (P < 0.01) of its infection rate with allele frequency of Est-2(100) and a negative correlation (P < 0.05) with allele Idh100.

Metabolic end-products in parasitic helminths and their intermediate hosts

Oxidoreductases which control the metabolic end-products in helminth parasites and their intermediate hosts were reviewed, in a trial to elucidate the respiratory metabolism during host-parasite associations. Special attention was given to Schistosoma parasites and their molluscan hosts.

Genetic variation among laboratory strains of the planorbid snail Biomphalaria glabrata

Isozymes of laboratory strains of Biomphalaria glabrata have been studied by starch gel electrophoresis. Methods are outlined for adaptation of this technique to the genetic study of these snails. Twenty-eight presumptive gene loci have been identified. Twelve invariant enzymes were observed. Sixteen loci displayed some polymorphism within or among the strains. These polymorphisms were generally widespread among strains from Brazil, Puerto Rico, St. Lucia, and the Dominican Republic. A high degree of intrastrain polymorphism was noted even in some presumably inbred laboratory strains. Crosses between strains were used to demonstrate the genetic basis for the patterns observed at 9 of the 16 polymorphic loci.

Enzyme electrophoresis and speciation of Schistosoma intermediate hosts

1. Enzyme electrophoretic patterns from populations of snails, intermediate hosts of Schistosoma, have been examined.

2. Esterase patterns (α-naphthyl butyrate as substrate) have been used to differentiate snail populations of B. africanus and Biomph. pfeifferi.

3. Malate, β-hydroxybutyrate and α-glycerophosphate dehydrogenases may be of use in some cases to distinguish between species, e.g. B. africanus v. B. ugandae and Biomph. sudanica v. Biomph. pfeifferi.