J.P. Grobler

A comparative biochemical genetic study of three populations of domesticated and wild African catfish (Clarias gariepinus)

Abstract 1. 1. Gene products of 22 protein coding loci in two commercially used (domesticated) and one wild population of African catfish, Clarias gariepinus, were examined by horizontal starch-gel and vertical polyacrylamide-gel electrophoresis. 2. 2. Average heterozygosities of 0.0759 and 0.0033 for the domesticated and 0.0467 for the wild catfish population were calculated. 3. 3. Genetic distances indicated a greater similarity between geographically isolated (hatchery) populations than between hatchery and wild populations. 4. 4. Selection of breeding stock for aquaculture practices based on the above information is discussed.

A comparison of growth performance and genetic traits between four selected groups of African catfish (Clarias gariepinus burchell 1822)

1. 1. Fast growing individuals (three groups) in a progeny batch of African catfish were identified and isolated from the main population. 2. 2. At the age of 36 weeks, the mean mass of two fast growing groups (169.6 and 232.0 g) was significantly (P < 0.05) higher than that of the rest of the population (88.8–108.7 g). 3. 3. A comparison of specific growth rates revealed that these differences were the result of superior growth at an early age. 4. 4. An electrophoretic evaluation of the different mass classes showed little or no difference between the LDH allele frequencies of the fast growing groups, but did indicate significant differences between the frequencies of fast and slow growing groups. 5. 5. The present study represents the first attempt to establish the role of genetic characteristics in the control of growth in African catfish, and suggests the feasibility of genetic selection for rapid growth in Clarias gariepinus.

Genetic diversity and isolation in African Buffalo (Syncerus caffer)

Abstract We studied genetic diversity in 58 buffalo from the Kruger National Park (KNP) and Willem Pretorius Nature Reserve (WPNR). Thirty-three protein-encoding loci were resolved; three were polymorphic. Average heterozygosity (H) values did not differ substantially between adult and sub-adult animals from the KNP (2.65 and 2.89%, respectively), but were lower in animals from the isolated WPNR herd (H = 1.48% and only 3% polymorphic loci compared to 9.1%). Representative levels of genetic diversity exist in the large but disease-carrying herd, whereas the smaller disease-free herds available for translocations appear less polymorphic.

Allozyme divergence among four representatives of the subfamily Alcelaphinae (family: Bovidae).

We used protein gel electrophoresis to study genetic diversity within and between blue wildebeest (Connochaetes taurinus), black wildebeest (C. gnou), red hartebeest (Alcelaphus buselaphus caama) and blesbok (Damaliscus dorcas phillipsi). Twenty-nine protein encoding loci were resolved, average heterozygosity ranged from 3.25-5.36% and between population gene diversity accounted for the major share of the total relative gene diversity (69.34%). Genetic distance values ranged from 0.021 to 0.132 and 0.029 to 0.136, with closest identity between the two wildebeest species (as expected for congeneric species). The results are discussed with specific reference to taxonomic relationships between species within the subfamily where interbreeding is known to have occurred.

Genetic variability in south african blue wildebeest (Connochaetes taurinus)

1. We use protein gel-electrophoresis to investigate genetic heterogeneity at 33 protein coding loci in a total of 46 blue wildebeest (C. taurinus) kept under different management regimes. 2. Average heterozygosity ranged from 2.14 to 4.3% and within-population differences accounted for 97.2% of total relative gene diversity. 3. Comparatively little divergence was found between animals sampled from populations with very diverse population sizes and management histories, with the largest genetic distance estimated between any two populations being only 0.0021. 4. We discuss our results with particular emphasis on the influence of management history on genetic diversity and divergence in C. taurinus.

Genetic diversity and differentiation of the three extant Southern African species of the subfamily Hippotraginae (family: Bovidae)

Abstract Protein gel-electrophoresis was used to assess genetic variability and allozyme divergence of the three species of the Hippotraginae from southern Africa. We stained for 18 protein coding loci, of which five displayed allelic polymorphism. Average heterozygosity ranged from 3.78% in sable antelope ( Hippotragus niger ) to 2.27% in gemsbok ( Oryx gazella ) and 1.86% in roan antelope ( H. equines ). Relative gene diversities were higher between (64.73%) rather than within (35.27%) populations, as expected for separate species. Genetic distances were determined following the methods of Nei (1972, American Naturalist 106 , 283–292) and Hillis (1984, Systematic Zoology 33 , 238–240). Values obtained using the latter method depicted known phylogenetic relationships more accurately when compared to clusters obtained using Neis (1972) method. The results obtained are discussed with specific reference to the influence of population history on current levels of genetic variability and the suitability of various measures of genetic distance distance to interspecific electrophoretic studies.

Genetic heterogeneity in sable antelope (Hippotragus niger Harris 1838) from four Southern African regions

Abstract Allozyme variability in four populations of sable antelope Hippotragus niger from southern Africa was determined by protein gel electrophoresis. Eighteen protein-coding loci, of which four displayed polymorphism, were resolved in blood samples obtained from 54 animals. Average heterozygosity ranged from 3.78% in a control group to as low as 1.53% in a small, isolated population. Within-population diversity constituted the major part of total gene diversity at 92.27%. Genetic distances confirmed that comparatively little divergence has occurred between the populations sampled, with a maximum genetic distance value of only 0.0044. We discuss the influence of early histories on current genetic characteristics in the populations sampled and present some guidlines towards optimal genetic management of H. niger .

Allozyme polymorphism and phenotypic variation in African catfish (Clarias gariepinus)

Abstract Genetic and morphological characteristics of African catfish ( C. gariepinus ) were evaluated to establish the association between allozyme polymorphism and the degree of variation found in morphological traits. A comparison of phenotypic variation and allozyme variability in catfish from two commercial batcheries revealed a positive correlation between genetic diversity and degree of phenotypic variation in six out of eight parameters evaluated. Variation in two morphological characteristics evaluated in groups of catfish reared under controlled environmental conditions also showed a positive correlation with allelic polymorphism. We conclude that phenotypic variation is affected by the degree of heterozygosity and discuss the implications of such relationships for the aquaculture industry.