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Biomedical subjects

T A Markow

Publications and source records attributed to T A Markow.

At least 19 recordsLinked to original sources
PubMed1995

Delayed male maturity is a cost of producing large sperm in Drosophila.

Among fruit-fly species of the genus Drosophila there is remarkable variation in sperm length, with some species producing gigantic sperm (e.g., > 10 times total male body length). These flies are also unusual in that males of some species exhibit a prolonged adult nonreproductive phase. We document sperm length, body size, and sex-specific ages of reproductive maturity for 42 species of Drosophila and, after controlling for phylogeny, test hypotheses to explain the variation in rates of sexual maturation. Results suggest that delayed male maturity is a cost of producing long sperm. A possible physiological mechanism to explain the observed relationship is discussed.

Animals↗
PubMed1992

Human handedness and the concept of developmental stability.

A model is proposed to explain the etiology of pathological handedness. Developmental instability, caused by elevated genotypic homozygosity, environmental disturbances, or their interaction, overrides programmed laterality and handedness in the same way that it perturbs the bilaterally symmetrical expression of morphological and metric traits. The model predicts that pathological handedness should be elevated among individuals with higher than average homozygosity and individuals who have developed under unfavorable uterine environments. Suggestions are offered for specific populations in which the predictions may be tested.

Functional Laterality↗
PubMed1992

Male size, developmental stability, and mating success in natural populations of three Drosophila species.

Morphological correlates of male mating success were assessed in natural populations of three Drosophila species. Mating males in D. simulans were larger than single males but were characterized by reduced developmental stability as indicated by fluctuating asymmetry. Mating male D. pseudoobscura were no larger than single males but exhibited significantly greater developmental stability. In D. mojavensis, however, mating males were larger and they showed a similar level of fluctuating asymmetry to that observed in single males. The differences observed between species are discussed in the context of their mating systems and reproductive ecology.

Animals↗
PubMed1991

Developmental stability in hybrids between the sibling species pair, Drosophila melanogaster and Drosophila simulans.

Drosophila melanogaster and its sibling species D.simulans were hybridized in the laboratory to test the hypothesis that developmental homeostasis in hybrids between two species having no prior gene flow would be significantly reduced. Developmental stability was assessed by measuring fluctuating asymmetry for three bilateral traits: sternopleural chaetae, wing length, and fronto-orbital plus frontal chaetae. Male F1 hybrids showed no decrease in developmental stability compared to males of parental species. Female hybrids showed significant fluctuating asymmetry compared to other flies. The results are discussed with respect to ideas about coadaptation and gene flow based upon previous studies of hybrid developmental stability.

Animals↗
PubMed1989

Fluctuating dermatoglyphic asymmetry in psychotic twins.

Fluctuating asymmetry of bilateral morphological traits is the result of prenatal developmental instability and has been shown to be greater in organisms having more homozygous genotypes (aabb vs. AaBb, for example). This expected increase in fluctuating asymmetry has been found among individuals having a high degree of liability for schizophrenia, as this disorder appears to have a polygenic basis. We tested the additional prediction that the greater genetic liability for schizophrenia necessary for concordance between twins should be associated with greater fluctuating asymmetry in twin pairs in which both twins are mentally ill compared to twin pairs in which one individual is normal. Our analysis of asymmetry for finger ridge counts from fingerprints of concordant and discordant pairs of twins supports this prediction and provides additional indirect support for the roles of polygenic transmission and prenatal epigenetic vulnerability in schizophrenia.

Adult↗
PubMed1989

Dermatoglyphic fluctuating asymmetry in twins and singletons.

The influence of twinning on developmental stability was measured by comparing fluctuating asymmetry in dermatologlyphic traits in monozygotic twins, dizygotic twins, and singletons. Despite reports that twinning has been reported to influence development of traits such as birth weight and I.Q., no significant difference in fluctuating asymmetry was found between different zygotic categories.

Dermatoglyphics↗
PubMed1988

Reproductive behavior of Drosophila melanogaster and D. nigrospiracula in the field and in the laboratory.

The reproductive behaviors of two species of fruit fly, Drosophila melanogaster and D. nigrospiracula, were compared in field and laboratory populations. A number of differences were observed in the behavior of the two species in their natural habitats. D. melanogaster, which was observed on citrus, mates at its feeding site, whereas D. nigrospiracula, which is cactiphilic, mates on a non-resource-based male territory adjacent to its feeding site. In both species large male size is important for reproductive success. However, in D. melanogaster smaller males tended to be excluded from the breeding site and were therefore not among the pool of potential mates to which females were exposed. Sex ratios were biased toward females in both species, but the high frequency of female remating in D. nigrospiracula may have provided more mating opportunities for the males of this species. Field observations differed from laboratory observations, and I discuss the importance of these differences for understanding the evolution of Drosophila mating systems.

Animals↗
PubMed1987

Behavioral and sensory basis of courtship success in Drosophila melanogaster.

In Drosophila some individuals are more successful at mating than others. Reproductive fitness is strongly dependent upon the ability to recognize and compete for members of the opposite sex. Experiments were designed to answer two questions. (i) What behavioral components are characteristic or predictive of successful courtship? and (ii) How important is the information transmitted in the different sensory channels for courtship success in each sex? These questions were approached by two experimental procedures. Flies having a sensory deficiency (olfactory, auditory, or visual) competed with wild-type flies of the same sex for mates. Males were found to rely upon sensory channels different from those used by females in order to court successfully. In addition, the courtships of pairs of various genotypes were recorded and subjected to multivariate analysis. The multivariate courtship profiles deviated most widely from those of successful wild-type pairs when the male or female was unable to receive information in the sensory channel most important for successful mating by that sex. Both sequential and quantitative courtship properties were altered when one participant was deficient in ability to receive certain sensory information.

Animals↗
PubMed1986

Fluctuating dermatoglyphic asymmetry and the genetics of liability to schizophrenia.

Schizophrenic subjects were compared to normal and psychiatric control subjects for degree of fluctuating asymmetry in two dermatoglyphic traits, a-b ridge count and fingertip pattern. The schizophrenic group exhibited significantly greater fluctuating asymmetry than either control group. Furthermore, indicators of disease severity such as early onset and declining course of illness correlated with degree of asymmetry. Both of these observations are expected if a disorder has a polygenic basis, since fluctuating asymmetry is a marker of polygenic inheritance.

Dermatoglyphics↗
PubMed1981

Genetic and sensory aspects of mating success of phototactic strains of Drosophila melanogaster.

In female choice experiments, Drosophila melanogaster males from a selected photonegative strain show a highly significant mating advantage over males from a photopositive strain. While photonegative behavior is sex linked in this species, the X chromosome is not involved in the mating advantage seen for this strain. The degree of the photonegative male advantage changes when tests are conducted with females mutant for olfaction and auditory perception but not when females are blind.

Animals↗
PubMed1981

Light-dependent pupation site preferences in Drosophila. II. Drosophila melanogaster and Drosophila simulans.

Drosophila melanogaster prefers to pupate in the dark, while its sibling species, D. simulans, prefers the light when the species are tested in isolation and when cultured and tested together. Reciprocal interspecific hybridizations were carried out and the F1 individuals were tested. Progeny from the cross of D. melanogaster females with D. simulans males chose pupations sites exactly intermediate between those of the two parental species, while the reciprocal-cross offspring preferred light pupation sites. The pupation site preferences (PSPs) of the hybrids are compatible with a sex-linked locus or loci influencing light-dependent PSP in this pair of species. Examination of light preferences of larvae prior to the late third instar demonstrates that these preferences are highly specific, being restricted to the time just before pupation. During the first two larval instars D. melanogaster is quite photopositive while D. simulans is comparatively photoneutral. These differences in light-dependent behaviour could aid in reducing competition between the two species.

Animals↗
PubMed1980

Relative male age, fertility, and competitive mating success in Drosophila melanogaster.

Female choice experiments were used to investigate the effect of relative male age on mating success in D. melanogaster. Experiments were conducted with a Canton-S (CS) strain, in which two virgin males of different ages (2, 4, or 8 days old) were offered to virgin females. Older males were found to be more successful under competitive conditions in another group of experiments, vermilion (v) males of different ages competed with CS males of different ages. The competitive success of v males was found to increase with their relative age. Male fertility at 2, 4, and 8 days of age was documented for both male genotypes mated with CS females. CS males fathered more offspring per copulation than v males, and the fertility of all males was found to increase with age. Discussion focuses on the changes in male mating success and fertility with age and genotype.

Age Factors↗