THE VARIABILITY IS IN THE SEX CHROMOSOMES

Sex differences in the mean trait expression are well documented, not only for traits that are directly associated with reproduction. Less is known about how the variability of traits differs between males and females. In species with sex chromosomes and dosage compensation, the heterogametic sex is expected to show larger trait variability (“sex‐chromosome hypothesis”), yet this central prediction, based on fundamental genetic principles, has never been evaluated in detail. Here we show that in species with heterogametic males, male variability in body size is significantly larger than in females, whereas the opposite can be shown for species with heterogametic females. These results support the prediction of the sex‐chromosome hypothesis that individuals of the heterogametic sex should be more variable. We argue that the pattern demonstrated here for sex‐specific body size variability is likely to apply to any trait and needs to be considered when testing predictions about sex‐specific variability and sexual selection.     

VARIABILITY IN THE YEAST HANSENULA HOLSTII

In the heterothallic yeast Hansenula holstii morphological variants consisting of a mother cell, stalk, and terminal cell are formed during vegetative growth. Tetrad distribution ratios of clones derived from mother and terminal cells differ. Preceding stalk formation endospore-like structures form in many cells. A causal relationship may exist between formation of the modified nuclei and change in the segregational patterns in the variants.     

THE GENETIC CONTROL OF PATHOGENICITY,SEROTYPES AND VARIABILITY IN PUCCINIA SORGHI

Flangas , A. L., and J. G. Dickson . (U. Wisconsin, Madison.) The genetic control of pathogenicity, serotypes and variability in Puccinia sorghi. Amer. Jour. Bot. 48(4): 275–285. Illus. 1961.—Four urediospore clones of P. sorghi were inbred through the alternate host, Oxalis, and the recombinant lines were compared with the mother clones for changes in pathogenicity and serological reaction. The aecial, inbred recombinant lines were scored for pathogenicity on 6 inbred lines of maize, 4 of which contained single, dominant alleles isolated from a single gene locus each conditioning differential rust reaction and Pop 35 and Pop 36, each with 2 recessive genes. The inbred, recombinant lines from each of the 4 mother clones reflected similar dimensional changes from original pathogenicity, that is, an ultimate gain or loss in host range or specificity. Based on reaction type incited on the 4 allelic differential hosts, continued inbreeding through 3 generations did not segregate homozygous pathogenic complements into distinct pathogenic biotypes. A similar array of pathogenic types was produced after each generation of inbreeding. The suppressed pathogenicity types in the dicaryotic line were revealed only through recombination. Hybridization between dicaryotic lines of selected pathogenic types of sibling and nonsibling pedigree confirmed the indeterminate nature of the pathogenic locus. The genetic basis of the commonly occurring mesothetic-X reaction (necrotic flecks and uredia of varying size surrounded by chlorotic and necrotic areas) is explained by the heterologous complementarity of fit of the interacting genic systems (genetic units). The heterologous mesothetic-X reactions offer ambiguous definition to the specificity state of the interaction and cannot be explained on the discrete gene-for-gene basis of rust reaction. Antisera produced from the pathogenic types differentiated the homologous from the heterologous combinations and revealed cross-reactions with P. graminis avenae. The comparative antigen constitution of the urediospore clones and the sibling recombinants thus far reveal a possible parallel existing between the modes of inheritance of pathogenic specificity and antigenic specificity.     

广西南丹中泥盆世三叶虫Ductina的蜕壳

Ductina vietnamila Maximova产于广西南丹罗富中泥盆统下部塘丁组上部,三叶虫化石多为原地埋葬,其中有一些为蜕壳标本。蜕壳构造的特征是:头胸分开,头前移并沿轴向错开、翻转180°;胸节基本按序排列,有时后两三个胸节前倾;胸与尾多分离,沿轴向微错开,有时尾向后翻转180°。     

CAENOGENESIS,DEVELOPMENTAL VARIABILITY,AND EVOLUTION IN THE CARPUS AND TARSUS OF THE MARBLED NEWT TRITURUS MARMORATUS

In this paper, after a comparative analysis of the development of Triturus marmoratus, we explore the existence of caenogenetic events and their ontogenetic and phylogenetic consequences. The adult morphology of the Triturus marmoratus limb, in terms of number and spatial arrangement of skeletal elements, agrees with the general pattern of urodeles. The congruence in the typical pattern of adult morphology does not hint at the striking differences in embryonic development. These differences can be summarized as follows: 1) Presence of a “central axis” that develops in a distal-to-proximal direction. It originates in the basale commune giving rise to the centrale and the intermedium. Thus, there is no postaxial branching as found in Ambystoma mexicanum. 2) Again, unlike in Ambystoma mexicanum, we find a postaxial structure composed of the ulnare (fibulare)-distal carpal (tarsal) 4-metacarpal (metatarsal) 4 which is independent of the “digital arch.” 3) The (forelimb) digits, in particular, digits 1, 2, and 3, undergo disproportionate elongation. For example, the second digit, composed of a thin continuous, cartilaginous rod, becomes longer than the rest of the limb. Our study of the patterns of embryonic connectivity suggests the coexistence of three directions of growth and morphogenesis in the development of the Triturus marmoratus limb. 1) A proximo-distal one that gives rise to the preaxial axis, “primary axis,” and individual digits. 2) An anterio-posterior axis of development that gives rise to the “digital arch” and determines the number of digits. 3) A disto-proximal central axis that originates in the basale commune and sequentially generates the centrale and the intermedium. We speculate that heterochronic interspecific variation in the time of onset of limb bud formation is related to the degree of precocious digital elongation. Selection for long extremities in early larval stages, associated with functional demands for locomotion and balancing, may be the cause for the above listed changes in developmental pattern. Thus, the reported system is an example of how selection during ontogeny can result in the evolution of the developmental process.     

水温变化对绥芬河滩头雅罗鱼产卵的影响

The Dace ( Leucisus brandti Dybowski) was a migration fish in Suifen river. The Dace can spawn at the water temperatures from 7℃ to 25℃. Changing of water temperature is the leading factor cause the spawning population to ovulate. However, high or low current water temperature had no obvious effectuation on ovulating behavior of Dace. The ovulation of the Dace often occurred in the evening or next morning after the water temperature rapidly in creased. The fish spawning often occurred as the water temperature decreased at first, after a period of steady low water temperature, then increased. A massive ovulating action began at the time. If the rising of water temperature happens only after a period of steady level without any decreasing of the water temperature, the change can not stimulate ovulation of the Daces. Usually, every large scale ovulate can sustain for 1 or 2 days. The peak time of ovulation often appears in 48 hours after the water temperature increases. Once the spawning population began to ovulate, their actions will be very intense, so that even catching action of human on them can not prevent the ovulation. The test of artificial induced ovulation showed that only when variation of water temperature were more than 10℃ ( increased degree+decreased degree), the Dace would ovulate. The Dace began to ovulate in 12～36 hours after the water temperature's change. The efficient time was shorter and the ovulation rate was higher the variation of water temperature were greater. At the range from 8℃ to 24℃, as high or low water temperature had no effect on the efficient time stimulating ovulate, the Dace can not ovulate out of the temperature range.