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Biomedical subjects

R E Page

Publications and source records attributed to R E Page.

At least 19 recordsLinked to original sources
PubMed2002

The genetic basis of the interspecific differences in wing size in Nasonia (Hymenoptera; Pteromalidae): major quantitative trait loci and epistasis.

There is a 2.5-fold difference in male wing size between two haplodiploid insect species, Nasonia vitripennis and N. giraulti. The haploidy of males facilitated a full genomic screen for quantitative trait loci (QTL) affecting wing size and the detection of epistatic interactions. A QTL analysis of the interspecific wing-size difference revealed QTL with major effects and epistatic interactions among loci affecting the trait. We analyzed 178 hybrid males and initially found two major QTL for wing length, one for wing width, three for a normalized wing-size variable, and five for wing seta density. One QTL for wing width explains 38.1% of the phenotypic variance, and the same QTL explains 22% of the phenotypic variance in normalized wing size. This corresponds to a region previously introgressed from N. giraulti into N. vitripennis that accounts for 44% of the normalized wing-size difference between the species. Significant epistatic interactions were also found that affect wing size and density of setae on the wing. Screening for pairwise epistatic interactions between loci on different linkage groups revealed four additional loci for wing length and four loci for normalized wing size that were not detected in the original QTL analysis. We propose that the evolution of smaller wings in N. vitripennis males is primarily the result of major mutations at few genomic regions and involves epistatic interactions among some loci.

Animals↗
PubMed2001

Responsiveness to sucrose affects tactile and olfactory learning in preforaging honey bees of two genetic strains.

Using sucrose solution as reward, we conditioned preforaging honey bees of two genetic strains to tactile stimuli or to odours. Acquisition, extinction of conditioned responses and discrimination between the conditioned stimuli and alternative tactile or olfactory stimuli were measured. Bees of the two genetic strains were selected for their foraging behaviour. In addition, they differ in their responsiveness to sucrose. To analyse the effects of sucrose perception on learning parameters independent of foraging behaviour, we conditioned preforaging bees of the two strains and compared their performance in tactile and olfactory learning paradigms. In both strains, acquisition in tactile and olfactory conditioning is determined by responsiveness to sucrose. There is no genetic effect on the relationship between responsiveness to sucrose and acquisition. Bees responding to low sucrose concentrations perform better than ones that only respond to higher concentrations. Extinction of conditioned responses correlates with acquisition. Responses to alternative stimuli are independent of responsiveness to sucrose.

Animals↗
PubMed2001

The effects of genotype, foraging role, and sucrose responsiveness on the tactile learning performance of honey bees (Apis mellifera L.).

We analyzed sucrose responsiveness and associative tactile learning in two genetic strains of honey bees under laboratory conditions. These strains differ in their foraging behavior. Bees of the "high" strain preferentially collect pollen. "Low"-strain bees mainly forage for nectar. Responsiveness to different sucrose concentrations and tactile learning were examined using the proboscis extension reflex. Acquisition, extinction of conditioned responses, and responses to an alternative tactile stimulus were tested. High-strain bees are more responsive to sucrose than low-strain bees. Regardless of genotype, pollen foragers are more responsive to sucrose than nectar foragers. In bees of both strains we find the same relationship between responsiveness to sucrose and acquisition. Bees responding to low sucrose concentrations show more often the conditioned response during acquisition than those responding only to higher sucrose concentrations. Extinction of conditioned responses depends on the response probability during acquisition. Discrimination between the two tactile stimuli is affected by genotype but not by responsiveness to sucrose. High-strain bees discriminate better than low-strain bees. Our experiments thus establish links between division of labor, responsiveness to sucrose, and associative learning in honey bees.

Animals↗
PubMed2001

Modulation of sucrose response thresholds in honey bees (Apis mellifera L.): influence of genotype, feeding, and foraging experience.

The perception of sugar is important to honey bees for making foraging decisions. We measured bees' perception by determining what concentration of sucrose touched to the antennae elicited the proboscis extension response (response threshold). A low response threshold (extension at low concentration) suggests a high perceptual value of sucrose. and vice versa. Perception of sucrose solutions differed between two artificially selected genotypic strains and was modulated by the bees' recent feeding experiences. Bees offered 10%, 30%, or 50% sucrose solutions in small cages overnight, and in large flight-cages or free-flying in the field for several days, had subsequent response thresholds positively correlated to the concentration offered. Empty bees, whether they were nectar, water or pollen foragers, dancers or non-dancers, had a significantly lower threshold than loaded bees. Crop volume affected response thresholds directly and independently of sucrose concentration. We interpret these findings as multiple mechanisms that operate in different time scales, modulating perception of sucrose. Changes occurred in the time scale of evolutionary processes as demonstrated by genotypic differences. Changes with foraging experience occur in hours or minutes while effects of crop filling are instantaneous.

Adaptation, Physiological↗
PubMed2001

Aging and development in social insects with emphasis on the honey bee, Apis mellifera L.

Honey bee colonies typically consist of about 20-40 thousand workers, zero to few thousand males (drones), depending on the time of year, and a single queen, the mother of the colony. Workers typically live 3-6 weeks during the spring and summer and can live about 4months during the winter. Queens are longer lived. Anecdotes of queens living 2-3years are not unusual, though they normally live less than a year in commercial hives. Little is known about the life span of drones. Queens develop from fertilized eggs that are not different from the eggs that develop into workers. Queens are, however, twice as large, have specialized anatomy, live much longer, and develop faster from egg to adult. All of these differences are derived from differences in larval rearing environment, primarily nutrition. The developmental trajectory of a female larva from worker into a queen can be determined as late as the third day of larval development, after this time the developmental pathway is fixed for a worker phenotype. The total time of larval development is only 5-6 days, therefore, just 2-3 days of differential feeding can lead to profound differences in development, and longevity. Workers undergo age development after they become adults. Workers usually initiate foraging behavior when they are 2-3 weeks old. The age at which a worker initiates foraging is a strong determinant of her length of life. This is presumed to be a result of the hazards of foraging, but natural senescence also occurs. Some bees remain in the nest and are never observed to forage, thereby outliving their forager sisters. Corresponding to this behavioral development are changes in the sizes of glands and the production of glandular products, increases in biogenic amine titers within the brain, an increase in the volume of specific regions of the brain, and changes in the neural system that affect perception of stimuli, and learning and memory. These age-related changes in behavior are regulated by intrinsic and extrinsic factors. Genetic variation has been demonstrated for many of these life history and behavioral traits. Selection and genome mapping studies have demonstrated relationships between the neural system, behavior, and life history traits.

Aging↗
PubMed2001

Fine scale mapping in the sex locus region of the honey bee (Apis mellifera).

Isolating an unknown gene with fine-scale mapping is possible in a "non-model" organism. Sex determination in honey bees consists of a single locus (sex locus) with several complementary alleles. Diploid females are heterozygous at the sex locus, whereas haploid males arise from unfertilized eggs and are hemizygous. The construction of specific inbred crosses facilitates fine scale mapping in the sex locus region of the honey bee. The high recombination rate in the honey bee reduces the physical distance between markers compared with model organisms and facilitates a novel gene isolation strategy based on step-wise creation of new markers within small physical distances. We show that distances less than 25 kb can be efficiently mapped with a mapping population of only 1000 individuals. The procedure described here will accelerate the mapping, analysis and isolation of honey bee genes.

Animals↗
PubMed2001

A linkage analysis of sex determination in Bombus terrestris (L.) (Hymenoptera: Apidae).

We constructed a linkage map of Bombus terrestris (Hymenoptera, Apidae) phase unknown. The map contains 79 markers (six microsatellite and 73 RAPD markers) in 21 linkage groups and spans over 953.1 cM. The minimal recombinational size of the B. terrestris genome was estimated to be 1073 cM. Using flow cytometry, the physical size of the haploid genome of B. terrestris was calculated to be 274 Mb. This is the second linkage map for a social insect species. Bombus terrestris has on average five times less recombinational events per kb than the honey bee Apis mellifera. Male haploidy, chromosome size, and eusociality can now be excluded as reasons for the high recombination frequency of Apis mellifera. Finally, the sex determination locus of B. terrestris was placed on the map using bulked segregant analysis.

Animals↗
PubMed1999

Tactile learning and the individual evaluation of the reward in honey bees (Apis mellifera L.).

Using the proboscis extension response we conditioned pollen and nectar foragers of the honey bee (Apis mellifera L.) to tactile patterns under laboratory conditions. Pollen foragers demonstrated better acquisition, extinction, and reversal learning than nectar foragers. We tested whether the known differences in response thresholds to sucrose between pollen and nectar foragers could explain the observed differences in learning and found that nectar foragers with low response thresholds performed better during acquisition and extinction than ones with higher thresholds. Conditioning pollen and nectar foragers with similar response thresholds did not yield differences in their learning performance. These results suggest that differences in the learning performance of pollen and nectar foragers are a consequence of differences in their perception of sucrose. Furthermore, we analysed the effect which the perception of sucrose reward has on associative learning. Nectar foragers with uniform low response thresholds were conditioned using varying concentrations of sucrose. We found significant positive correlations between the concentrations of the sucrose rewards and the performance during acquisition and extinction. The results are summarised in a model which describes the relationships between learning performance, response threshold to sucrose, concentration of sucrose and the number of rewards.

Animals↗
PubMed1999

The effect of genotype, age, sex, and caste on response thresholds to sucrose and foraging behavior of honey bees (Apis mellifera L.).

Bees derived from artificially selected high- and low-pollen-hoarding strains were tested for their proboscis extension reflex response to water and varying sucrose concentrations. High-strain bees had a lower response threshold to sucrose than low-strain bees among pre-foragers, foragers, queens and drones. Pre-foraging low-strain workers showed ontogenetic changes in their response threshold to sucrose which was inversely related to age. High-strain foragers were more likely to return with loads of water compared to low-strain foragers. Whereas low-strain foragers were more likely to return with loads of nectar. Low-strain nectar foragers collected nectar with significantly higher sucrose concentrations than did the high-strain nectar foragers. Alternatively, low-strain foragers were more likely to return empty compared to high-strain foragers. These studies demonstrate how a genotypically varied sensory-physiological process, the perception of sucrose, are associated with a division of labor for foraging.

Aging↗
PubMed1999

Unusually high recombination rate detected in the sex locus region of the honey bee (Apis mellifera).

Sex determination in Hymenoptera is controlled by haplo-diploidy in which unfertilized eggs develop into fertile haploid males. A single sex determination locus with several complementary alleles was proposed for Hymenoptera [so-called complementary sex determination (CSD)]. Heterozygotes at the sex determination locus are normal, fertile females, whereas diploid zygotes that are homozygous develop into sterile males. This results in a strong heterozygote advantage, and the sex locus exhibits extreme polymorphism maintained by overdominant selection. We characterized the sex-determining region by genetic linkage and physical mapping analyses. Detailed linkage and physical mapping studies showed that the recombination rate is <44 kb/cM in the sex-determining region. Comparing genetic map distance along the linkage group III in three crosses revealed a large marker gap in the sex-determining region, suggesting that the recombination rate is high. We suggest that a "hotspot" for recombination has resulted here because of selection for combining favorable genotypes, and perhaps as a result of selection against deleterious mutations. The mapping data, based on long-range restriction mapping, suggest that the Q DNA-marker is within 20,000 bp of the sex locus, which should accelerate molecular analyses.

Animals↗
PubMed1999

Mapping of hybrid incompatibility loci in Nasonia.

According to theory, F(2) hybrid breakdown (lethality or sterility) is due to incompatibilities between interacting genes of the different species (i.e., the breaking up of coadapted gene complexes). Detection of such incompatibilities is particularly straightforward in haplodiploid species, because virgin F(1) hybrid females will produce haploid recombinant F(2) males. This feature allows for screening of the complete genome for recessive genetic incompatibilities. Crosses were performed between Nasonia vitripennis (v) and its sibling species N. giraulti (g). First, a linkage map was produced using RAPD markers. RAPD markers showed an overall bias toward vitripennis alleles, a pattern not predicted by the basic two-interactor Dobzhansky-Muller model. Recovery patterns of visible markers were consistent with those of linked RAPD markers. If particular genetic interactions between two loci are causing hybrid lethality, then those genotypes should be underrepresented or absent among adult F(2) males. Four sets of significant incompatibilities were detected by performing pairwise comparisons of markers on different chromosomes. Likely explanations for the observed patterns are maternal effect-zygotic gene incompatibilities or clustering of incompatibility loci. Due to the short generation time, advantages of haplodiploidy, and availability of markers, Nasonia promises to be a productive system for investigating the genetics of hybrid inviability.

Animals↗
PubMed1998

The effect of genotype on response thresholds to sucrose and foraging behavior of honey bees (Apis mellifera L.).

Honey bee foragers were tested for their proboscis extension response (PER) to water and varying solutions of sucrose. Returning pollen and nectar foragers were collected at the entrance of a colony and were assayed in the laboratory. Pollen foragers had a significantly higher probability of responding to water and to lower concentrations of sucrose. Bees derived from artificially selected high- and low-pollen-hoarding strains were also tested using the proboscis extension assay. Returning foragers were captured and tested for PERs0 to 30% sucrose. Results demonstrated a genotypic effect on PERs of returnining foragers. The PERs of departing high- and low-strain foragers were consistent with those of returning foragers. The PERs were related to nectar and water reward perception of foragers. High strain bees were more likely to return with loads of water and lower concentrations of sucrose than foragers from low pollen strain. Low-strain bees were more likely to return empty. We identified a previously mapped genomic region that contains a variable quantitative trait locus that appears to influence sucrose response thresholds. These studies demonstrate a gene-brain-behavior pathway that can be altered as a consequence of colony-level selection for quantities of stored food.

Animals↗