Uzi Ritte

Activity pattern and rhythm in the subterranean mole rat superspecies Spalax ehrenbergi.

Good candidates for naturally occurring variability in circadian rhythms may be subterranean herbivores, since they are not normally subjected to entraining light stimulation. To test this possibility, we selected the blind mole ratSpalax ehrenbergi superspecies in Israel and tested it in short- and long-term experiments. Short-term experiments showed that the animals exhibited three patterns of activity: a regular circadian rhythm (26.6%), an altered circadian rhythm (shorter or longer than normal, 53.1%), and an arrhythmic pattern (20.3%). A long-term experiment showed that the arrhythmic pattern indeed reflected a genuine arrhythmic genotype. The mole rats were found to be active less than 25% of the day and exhibited a multiphasic mode of activity, both diurnally and nocturnally. The number of activity periods and the level of activity were negatively correlated: Animals that exhibited a high level of activity per unit of time showed low numbers of activity periods, while animals that exhibited a lower level of activity showed higher numbers.

The differences among Jewish communities—Maternal and paternal contributions

The haplotypes of Y chromosome (paternally inherited) and mtDNA (maternally inherited) were analyzed in representatives of six Jewish communities (Ashkenazic, North African, Near Eastern, Yemenite, Minor Asian/Balkanian, and Ethiopian). For both elements, the Ethiopian community has a mixture of typically African and typically Caucasian haplotypes and is significantly different from all others. The other communities, whose haplotypes are mostly Caucasian, are more closely related; significant differences that were found among some of them possibly indicate the effects of admixture with neighboring communities of non-Jews. The different contribution of the Y chromosome and mtDNA haplotypes to the significant differences among the communities can be explained by unequal involvement of males and females in the different admixtures. In all communities, except the Ethiopians, the level of diversity (ĥ) for Y chromosome haplotypes is higher than that for mtDNA haplotypes, suggesting that in each community the people who become parents include more males than females. An opposite proportion (more females than males) is found among the Ethiopians.

The dynamic of the t -haplotype in wild populations of the house mouse Mus musculus domesticus in Israel

The t-haplotype, a variant of the proximal part of the mouse chromosome 17, is composed of at least four inversions and is inherited as a single genetic unit. The haplotype causes embryonic mortality or male sterility when homozygous. Genes within the complex are responsible for distortion of Mendelian transmission ratio in males. Thus, the t-haplotype in heterozygous males is transferred to over 95% of the progeny. We examined the dynamic and behavior of the t-haplotype in wild populations of the house mouse in Israel. The Israeli populations show high frequency (15%–20%) of both partial and complete t-carrying mice, supporting the suggestion that the t-complex evolved in the M. domesticus line in the Israeli region. In one population that had the highest frequency of t-carrying individuals, we compared the level of gene diversity between t-carrying and normal mice in the marker’s loci: H-2 locus of the major histocompatibility complex (MHC) on the t-haplotype of chromosome 17, three microsatellites on other chromosomes, and the mitochondrial D-loop. Genetic variability was high in all tested loci in both t and (+) mice. All t mice carried the same chromosome and showed the same H-2 haplotype. While t-carrying mice showed significant H-2 heterozygotes access, (+) mice expressed significant H-2 heterozygote deficiency. There were no differences in the level of gene diversity between t and (+) mice in the other loci. Heterozygosity level at the MHC may be an additional factor in the selective forces balancing the t-haplotype polymorphism.

Foraging pressure of the Nubian ibex Capra ibex nubiana and its effect on the indigenous vegetation of the En Gedi Nature Reserve, Israel.

Abstract The population of the Nubian ibex Capra ibex nubiana in the En Gedi Nature Reserve, Israel, is divided into several herds. In a study lasting from December 1978 to May 1981, the herds moved every day along an established route, from a fixed sleeping area to the activity areas. The size of their home range was very small, about 0·5 km 2 . Feeding activities constituted about one half of their time. Ibex in En Gedi prefer grazing, and their impact on the perennial plants therefore depends on the amount and spread of rain — in good winters they feed mostly on annuals, and browsing pressure on perennials is minimal. It is highest during the summer months, from June to November. While browsing, the ibex are flexible in their diet, feeding on most perennial species, 40% of which are of Sudanian origin. Five species can be defined as principal food plants: Acacia raddiana, Ziziphus spina-christi, Salsola vermiculata, Pennisetum asperifolium and Moringa peregrina. Moringa, which is a ‘rare’ species, was the most sensitive to ibex browsing, and had a low rate of regeneration.

Origins of H-2 polymorphism in the house mouse. II. characterization of a model population and evidence for heterozygous advantage

Comparison of the rate of synonymous and nonsynonymous nucleotide substitutions suggests that certain regions of the functional H-2 genes, which are part of the mouse major histocompatibility complex (Mhc), are under strong positive selection pressure. Thus far, however, little evidence has been provided for the existence of such pressure in natural mouse populations. We have, therefore, initiated experiments designed to test the hypothesis of positive selection acting on H-2 loci. The experiments are being carried out on two natural mouse populations in Jerusalem, Israel. One population occupies a space of about 100 m2 in a chicken coop, the other lives in a nearby field in which “mouse stations” providing food and shelter have been set up. Extensive typing of these two populations revealed the presence of only four H-2 haplotypes. Mice in the two populations breed continually all year around, yet population size varies seasonally, with population maxima in winter and minima in summer. The population in the chicken coop contains a relatively stable nucleus which may be organized in demes with an excess of females over males and limited territorial mobility. The rest of the mice stay in the population for a short time only and then either die or emigrate. The field population is smaller and more loosely organized than the chicken-coop population, with demes probably forming only during population maxima. For the rest of the time breeding in this population is probably panmictic. At a population minimum in the summer of 1984, H-2 homozygotes happened to predominate over heterozygotes. This situation, however, lasted for a short time only and thereafter there was a continuous, statistically highly significant increase in the proportion of H-2 heterozygotes of one or two types. The increase occurred in both populations but was more apparent in the chicken-coop population. This observation provides the first experimental evidence that heterozygous advantage might be one of the mechanisms maintaining high H-2 polymorphism in natural populations of the house mouse.

East asian hemoglobin type (Hbbp) in wild populations of the house mouse in Israel

Electrophoretic studies of hundreds of individuals showed that all wild populations of the house mouse in Israel are polymorphic for alleles Hbbd and Hbbpof the hemoglobin locus. No mouse carrying Hbbswas found. This finding contradicts the notion that Hbbpis limited to East Asian house mice.

The genetic basis of egg lay response to conditioned medium in the flour beetle, Tribolium castaneum : I. Two-way selection.

SummaryThe rate of egg laying in Tribolium castaneum is affected by the quality of the environment and can thus serve not only as a component of fitness of the individual, but also as an adaptation to the long-term survival of the population. In an attempt to determine whether it is an independent genetic character, selection for high and low rates of response was carried jut in beetles from three wild populations. When tests were done on virgin females, and responsiveness, corrected for scale effects, was used as the criterion for selection, separation between the lines was achieved in one generation. It is suggested that in natural populations of Tribolium, the responsiveness of the rate of egg laying to the quality of the environment is controlled by a small number of genes.

Circadian rhythm and theper ACNGGN repeat in the mole rat,Spalax ehrenbergi

Individual variability in circadian locomotor activity has recently been discovered in the blind mole rat,Spalax ehrenbergi. An interesting association was found between different circadian activity types and two DNA fragments, 5.6 and 5.9 kb long, that contain the ACNGGN repeat sequence, homologous to a part of theperiod gene ofDrosophila. Nine of 12 arrythmic animals showed the 5.6-kb band, while 13 of 17 circadian rhythmic animals had the 5.9-kb band. This repeat exists also in the brain RNA of the mole rat, apparently in higher quantities during the sleeping phase, suggesting that an unusual protein(s), composed of a poly-Thr-Gly segment, affects its circadian rhythm.

The influence of the ability to disperse on generation length and population size in the flour beetle, Tribolium castaneum

Abstract. 1 In Tribolium castaneum Herbst, in which dispersal is genetically determined, it is possible to select for strains that are characterized by high and low dispersal, High dispersal (HD) beetles are better adapted than low dispersal (LD) beetles for colonization, as can be seen from differences that exist between the two groups with regard to several life‐history parameters. 2 Comparisons were made between the dynamics of seventy‐two HD and seventy‐two LD populations. Generation length in HD populations was significantly shorter than in LD populations. After 91/2 weeks, in open treatments (from which dispersal away from the set was allowed), HD populations had more beetles than LD populations, whereas in closed treatments (from which dispersal away from the set was not allowed) the opposite was true. 3 These findings may explain the maintenance of the genetic variability of dispersal behaviour in natural populations of T.castmeurn.

Low H-2 polymorphism in some Israeli wild mouse populations

Two populations of the wild house mouse, Mus domesticus, found living close to each other (one inhabited a chicken coop and the other an open field at the Educational Farm of the Hebrew University of Jerusalem, East Talpiot, Jerusalem) were studied for their H-2 polymorphism. These two populations were selected because they are well characterized in terms of their ecological parameters; they have been under continuous surveillance for several years. Twenty-seven H-2 homozygous lines were produced by mating wild mice from these two populations with laboratory strains. The H-2w homozygotes were then characterized by serological typing with monoclonal and polyclonal antibodies specific for the known allomorphs controlled by the class I H-2K and H-2D loci or the class II H-2A and H-2E loci. They were also used as donors for immunizations and for the selection of antisera defining the H-2 haplotypes carried by these lines. Four new H-2 haplotypes could be identified: H-2w82 (Kwl6 Dws2) H-2w83 (Kw83 Dw16) H-2w84 (Kw84 Dw84) and H-2w85 (Kw83Dw84) the last haplotype being a recombinant derived from H-2w83 and H-2w84. Antinsera defining the new haplotypes were then used for a study of the wild populations. This study revealed that the populations contain only the four identified H-2 haplotypes, having three alleles at the H-2K locus (Kw16 Kw83, Kw84) and three alleles at the H-2D locus (Dw16, Dw82 and Dw84). The alleles occur in the populations with a frequency of 0.12–0.54. There were no significant differences in gene frequencies between the two populations, and the allele frequencies remained more or less stable. There was a significant excess of heterozygotes for at least some of the genes, compared with the frequency expected from Hardy-Weinberg equilibrium. The same antisera were also used to type other populations in the vicinity of Jerusalem. In one population, located 30 km west of Jerusalem, the mice failed to react with any of the reagents. In the other two populations, located 15 km west and 40 km northeast of Jerusalem, three of the four H-2 haplotypes found in East Talpiot were present at high frequencies. It appears, therefore, that only three main H-2 haplotypes and two or three minor ones are present in the area around Jerusalem. This study thus provides the first example of a large mainland population in which the H-2 polymorphism is comparable to that of many other non-H-2 loci.