Simulating Natural Conditions in the Laboratory: A Re-Examination of Sexual Isolation between Sympatric and Allopatric Populations of Drosophila pseudoobscura and D. persimilis

Simulating natural conditions in the laboratory poses one of the most significant challenges to behavioral studies. Some authors have argued that laboratory “choice” experiments reflect mate choice in nature more accurately than “no-choice” experiments. A recent choice experiment study questioned the conclusions of several earlier studies by failing to detect a published difference in sexual isolation between populations of Drosophila pseudoobscura, and suggested their result was more robust because of the more realistic design. Here, we re-examine the methods and analyses of this recent study, and we find there was indeed a difference in sexual isolation between populations of D. pseudoobscura. We also conduct a more rigorously controlled choice experiment and, in agreement with previous studies, note that D. pseudoobscura females from populations sympatric to their sibling species, D. persimilis, exhibit greater sexual isolation than those from allopatric populations. Our results confirm the existence of a geographic pattern in sexual isolation in D. pseudoobscura, and we discuss differences in experimental designs in light of the biology of this species.     

Relative performance of the two hands in simple and choice reaction time tasks

There is evidence that the left hemisphere is more competent for motor control than the right hemisphere. This study investigated whether this hemispheric asymmetry is expressed in the latency/duration of sequential responses performed by the left and/or right hands. Thirty-two right-handed young adults (16 males, 16 females; 18-25 years old) were tested in a simple or choice reaction time task. They responded to a left and/or right visual target by moving their left and/or right middle fingers between two keys on each side of the midline. Right hand reaction time did not differ from left hand reaction time. Submovement times were longer for the right hand than the left hand when the response was bilateral. Pause times were shorter for the right hand than the left hand, both when the responses were unilateral or bilateral. Reaction time results indicate that the putatively more efficient response preparation by the left hemisphere motor mechanisms is not expressed behaviorally. Submovement time and pause time results indicate that the putatively more efficient response execution by the left hemisphere motor mechanisms is expressed behaviorally. In the case of the submovements, the less efficient motor control of the left hand would be compensated by a more intense attention to this hand.     

Responses of male mice to odors of females: Effects of T- and H-2-locus genotype

Male wild house mice (Mus musculus) were given a choice of odors of females whose T-locus genotype was +/ + or +/t. Males showed strong preferences for the odors of +/ + females. However, when males were tested with odors of recombinant females whose genotype differed at the T locus but which carried similar haplotypes at the H-2 locus, the preference for odors of +/+ females was not manifested. Consequently, differences in female odor production that are responsible for male odor preference are not due specifically to the female genotype at the T locus.This work was partially supported by NIH Grant HD R01 1997 and a BRSG Grant from Rutgers University.     

Genetic and sensory aspects of mating success of phototactic strains ofDrosophila 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.Supported by NIH Grants GM 25424 and NS 15263.     

Genetic evidence that ovulation reduces sexual receptivity inDrosophila melanogaster females

Drosophila females start ovulation shortly after mating, and at the same time they become unreceptive to courting males. Both physiological changes are induced by the “sexpeptide” derived from the male accessory glands. It is conceivable, therefore, that the first effect of the peptide is to induce ovulation, and some signal derived from ovulated eggs makes females unreceptive. To test this hypothesis, I examined the mating receptivity of virginD. melanogaster females homozygous forlozenge mutants that showed a high-frequency spontaneous ovulation. These females were reluctant to mate. However, when mature eggs were genetically deprived using nonallelic female sterile mutants, their receptivity increased significantly, although mating speed was still slower than that of normal virgin females. Essentially the same was found with the females that were ectopically expressing the sex-peptide gene. The results indicate that ovulation induced by the sex-peptide has an effect of reducing the sexual receptivity of mated females.     

Neonatal exposure to short days and low temperatures blunts stress response and yields low fluctuating asymmetry in Siberian hamsters

Fluctuating asymmetry (FA) refers to small, non-directional deviations from perfect bilateral symmetry in morphological characters. Individuals with low FA presumably either developed in a relatively stable environment and/or were better able to buffer against developmental stressors. The present study investigated the effects of seasonal factors measured by day length and ambient temperature manipulations on the development of bilateral characters and concomitant changes in stress responses. Siberian hamsters were exposed to either long days (16 h of light per day) or short days (8 h of light per day) combined with either standard temperatures (21+/-2 degrees C) or low temperatures (8+/-2 degrees C) on the day of birth until weaning. Cortisol concentrations at baseline and following acute restraint stress, and FA values were measured in adulthood. Females reared in winter-like conditions with short day lengths and low temperatures had low FA and low cortisol concentrations following restraint stress compared to other females. Females reared in long day lengths and standard temperatures had the highest rate of increase in cortisol concentrations after restraint among other female groups. No group effects were observed in males regarding day length and temperature manipulations. Baseline and post-restraint cortisol concentrations were higher in females than males for all groups except in animals reared in short day lengths and low temperatures. Our results suggest that winter-like conditions during neonatal period evoke hyposensitivity to stress in adult females and this blunted response to stress is a key factor in achieving ideal growth patterns.     

Food selection changes under stress

Two studies investigate the effect of stress on food choice. Experiment 1 demonstrates experimentally that stress causes changes in food choice away from healthy low fat foods (grapes) to less healthy high fat foods (M&Ms), confirming previous survey research. Experiment 2, a survey study, finds that more females than males report increasing food consumption when stressed. A much larger percentage of those who report increasing their food consumption when stressed (71%) are restrained eaters (i.e., dieters) than are people who undereat or who do not change the amount they eat when stressed (35%). The foods that they report overeating when stressed are foods they normally avoid for weight-loss or health reasons (i.e., highly caloric high fat snack foods). They report eating these foods to feel better. Both studies show that stress not only increases consumption in certain individuals but also shifts their food choice from lower fat to higher fat foods.     

基于3D偏差分析的成人桡骨远端解剖对称性研究

目的　通过形态学测量方法评估成人桡骨远端解剖的对称性。 方法　采集15例正常志愿者的双侧前臂薄层CT扫描数据,对桡骨远端1/3的骨性结构进行三维重建,以模型体积和表面积作为目标参数对每一例志愿者左、右侧桡骨的三维模型进行解剖测量;进一步通过3D偏差分析方法完成双侧桡骨模型解剖对称性的定量化和可视化分析。 结果　左、右侧桡骨远端表面积最大差异小于5.6%（P=0.004）,体积差异小于9.1%（P=0.005）;3D偏差分析结果显示,受试者的最大平均负偏差为-0.40 mm,最大平均正偏差为0.34 mm;3D偏差较大的区域主要分布在桡骨远端的非关节面部位。 结论　成人桡骨远端在关节面形态方面具有高度的解剖对称性,临床上对于桡骨远端关节内骨折的外科解剖重建,采用健侧桡骨镜像模型作为参考对象有利于指导桡骨远端骨折的精准复位重建,这对于术后桡腕关节功能的恢复具有重要意义。     

No Apparent Indirect Genetic Benefits to Female Red Flour Beetles Preferring Males with Intense Copulatory Courtship

Whether females gain indirect genetic benefits through mate choice is a controversial issue since this requires additive genetic variance in the preferred male traits. Condition dependence could maintain the necessary genetic variance by linking the expression of male traits to the supposedly large number of genes affecting condition. Copulating males of the red flour beetle Tribolium castaneum rub their legs along the female elytra. Females favor males with vigorous rubbing through cryptic female choice. We measured the repeatability and heritability of this behavior and assessed its potential use as indicator of viability and condition. We found genetic variance in larval to adult survival and in the rate of leg rubbing in males. However, the rate of leg rubbing was not related to offspring survival or condition dependent. The genetic variance in leg rubbing was mostly non-additive with very low narrow sense heritability. Therefore, we failed to document any indirect genetic benefits to choosy females through viability of their offspring or attractiveness of their sons.     

Variability of origin of serratus anterior muscle in Japanese.

The observations on 567 male and 251 female Japanese cadavers revealed that there was a wide variation of the lowermost origin of the serratus anterior muscle ranging from the 6th to the 12th rib. The most frequent cases in males were of the 8th rib type (42.5%), whereas those in females were of the 9th rib type (43.3%). There was a statistically significant difference in the distribution of the muscle origin between the sexes. The observations also showed that bilateral symmetry of the muscle origin was preponderant over asymmetry, the symmetric cases forming about seven-tenths of all individuals without sex distinction.     

人体双侧对称经络电阻抗失衡与疾病的相关研究

通过实验装置,分别测量人体双侧对称经络对称两穴位之间的电流波形,计算其电阻抗值,探讨经络的导电特性。证明了正常人双侧经络电阻抗的对称性、经络循行线的低阻性及双侧经络电阻抗失衡与其络属脏器病变的相关性等问题     

The medial preoptic area is necessary for motivated choice of pup- over cocaine-associated environments by early postpartum rats

Converging evidence suggests that the motivation to seek cocaine during the postpartum period is significantly impacted by the competing incentives of offspring, a stimulus unique to this life stage. In the present study, the functional role of the medial preoptic area (mPOA), a critical site involved in maternal responsiveness, on processing incentive value of pup-associated cues and influencing response allocation for pup- over cocaine-associated environments was investigated using a concurrent pup/cocaine choice conditioned place preference (CPP) paradigm. Early postpartum females with bilateral guide cannulae aimed into the mPOA or into anatomical control sites were conditioned, from postpartum days (PPD) 4 to 7, to associate different uniquely featured environments with pups or cocaine. CPP was tested on PPD8 following intra-mPOA infusions of either 2% bupivacaine or saline vehicle. In two additional experiments, the effects of intra-mPOA infusions of bupivacaine on expression of conditioned responding induced by environments associated with either pups or cocaine were examined separately. Transient inactivation of the mPOA selectively blocked the conditioned preferences for pup-associated environments, significantly contrasting the robust pup-CPP found in non-surgical and intra-mPOA vehicle-treated females. In contrast, mPOA inactivation failed to alter cocaine-CPP in postpartum females. When given a choice between environments associated with pups or cocaine, transient functional inactivation of the mPOA altered choice behavior, biasing the preference of females toward cocaine-associated environments, such that almost all preferred cocaine- and none the pup-associated option. The anatomical specificity was revealed when inactivation of adjacent regions to the mPOA did not affect CPP responses for pups. The findings support a critical role for the mPOA in mediating pup-seeking behavior, and further suggest that the competing properties of pups over alternative incentives, including drugs of abuse, rely on mPOA integrity to provide relevant pup-related information to the circuitry underlying the choice behavior between pups and alternative stimuli.     

Development and evaluation of a semi-automatic technique for determining the bilateral symmetry plane of the facial skeleton

During reconstructive surgery of the face, one side may be used as a template for the other, exploiting assumed bilateral facial symmetry. The best method to calculate this plane, however, is debated. A new semi-automatic technique for calculating the symmetry plane of the facial skeleton is presented here that uses surface models reconstructed from computed tomography image data in conjunction with principal component analysis and an iterative closest point alignment method. This new technique was found to provide more accurate symmetry planes than traditional methods when applied to a set of 7 human craniofacial skeleton specimens, and showed little vulnerability to missing model data, usually deviating less than 1.5° and 2 mm from the intact model symmetry plane when 30 mm radius voids were present. This new technique will be used for subsequent studies measuring symmetry of the facial skeleton for different patient populations.     

Season of birth and fluctuating asymmetry.

Fluctuating asymmetry (FA) refers to random, small deviations from perfect bilateral symmetry in morphological traits. These minor deviations from the ideal phenotype reflect environmental and genetic perturbations experienced during ontogeny. FA has been associated with negative health outcomes and many developmental disorders in humans. The prevalence of developmental disorders and adult health vary according to the month of birth, suggesting that seasonal stressors may leave enduring signs in the adult body, marked by high FA. The current study examined the relationship between FA and birth season. Data were collected for 205 males and females (average age = 20.39 years) on FA of 10 bilateral traits (second, third, fourth, and fifth digit length, palm height, wrist diameter, elbow width, ear height, foot breadth, and ankle circumference). Additional relationships were also investigated among FA, testosterone (T), and birth order. Results indicate that ear FA was lower for fall births compared to winter births in males. In females, palm FA was lower for fall births compared to those of the spring. FA of the digits was positively associated with T in males. Average FA, excluding the digits, decreased as the number of maternal siblings increased for both sexes. T concentrations in males were positively associated with the number of younger brothers. Our results generally confirm previous research on seasonal variation in adult longevity and neurological and psychiatric disorders, suggesting that winter and spring births are at risk for asymmetric developmental trajectory.     

Variation of Female Preference for Male Coloration in the Eastern Mosquitofish Gambusia holbrooki

The preference for melanistic males was studied in two populations of eastern mosquitofish (Gambusia holbrooki, Pisces: Poeciliidae), one from Florida and one from northern Italy. Melanism in the eastern mosquitofish is a Y—linked character, expressed in males only. Melanistic males have black spots varying in size and number. In the Florida population, melanistic males are common, whereas in the Italian population they have never been observed. Females were male-deprived for at least 2 months before being tested in a dichotomous choice chamber. Italian females showed a significant preference for unpigmented males from their own population, whereas Florida females preferred melanistic males. When given the choice between males with few (<10% of the body surface) and males with many (>50%) black spots, Italian females preferred males with few black spots and Florida females those with many black spots. The preference of the Italian females for unpigmented males was confirmed in females reared from birth to maturity in the presence of only melanistic males. The preference of Florida females for melanistic males was also confirmed in females reared from birth to maturity in the presence of only unpigmented males. Altogether, these results demonstrate that in the eastern mosquitofish there is polymorphism in female preference and that this preference does not have an environmental basis.     

Sexual selection inNauphoeta cinerea: Inherited mating preference?

In the cockroach,Nauphoeta cinerea, female preferences with respect to sexual selection can be easily examined. Mating is nonrandom due to female preferences based on olfactory differences among males. This mate choice results in a mating advantage for socially dominant males. In this paper, results of experiments designed to explore the relationship between female choice in daughters and the preferred male character are described. Using females with male parents of known status and an olfactometer to determine preferences, it is shown that the type of male preferred depends on the status of the female's father. Because social experiences of females were experimentally controlled, these preliminary results suggest that (1) variation in female preferences may have a genetic basis and (2) because of assortative mating, mate choice may be genetically linked to the preferred male character, as predicted by mathematical models of the sexual selection process.N. cinerea appears to be an ideal species for testing predictions and assumptions of models of sexual selection.This research has been supported by a NIMH training grant in behavioral genetics (MH16680), administered by the Institute for Behavioral Genetics, University of Colorado.     

Genetic variation in “first” male effects on egg laying and remating by femaleDrosophila melanogaster

MaleDrosophila melanogaster from lines artificially selected to have divergent life histories were tested to determine if they differed, in their effects on female reproductive behavior. During the first 5 days after mating, males from short-generation populations caused females to lay eggs at a faster rate than did males from long-generation populations. This faster oviposition rate resulted in greater numbers of adult progeny produced by short-generation males. During the period 6–21 days after mating, long-generation males fathered more adult progeny. Females that were first mated to short-generation males were more likely to remate than were females first mated to long-generation males. Rematings were interrupted in order to prevent transfer of second-male accessory fluid and sperm. Females that were first mated to long-generation males produced more progeny after interrupted matings than did females that were first mated to short-generation males.     

Genetic analysis ofDrosophila melanogaster egg insertion behavior

The tendency ofDrosophila melanogaster females to insert eggs into the substrate was analyzed by a diallel cross among five inbred lines from different geographic origins. The trait showed a great deal of additive genetic variation. The directional dominance effect was found to be large, indicating past directional selection for a strong tendency to insert eggs into the medium. Some maternal effect may also be present. Contrary to Takamura and Fuyama (Behav. Genet. 10:105–120, 1980), no relation was found between the tendency to insert eggs in the medium and the choice between a hard (paper) or soft (culture medium) oviposition surface. Lines, which did differ in the tendency to bury their eggs did not differ in the choice of oviposition site.     

Selection for increased female sexual receptivity inRaised stocks ofDrosophila melanogaster

Two third-chromosome mutations inraised (rsd) stocks, when homozygous, cause the wings ofDrosophila melanogaster adults to be held upright. Males expressing these mutations cannot vibrate their wings to produce the courtship song, which functions to increase female receptivity to copulation. As expected,rsd males are less successful when courting wild-type females. However, females from long-establishedrsd stocks are more receptive to courtship stimuli and mate more readily with bothrsd and wild-type males than do wild-type females. Genetic analysis reveals dominant factors on the X and third chromosomes that, in combination, are responsible for the increased receptivity ofrsd females. These observations suggest that the lack of courtship song inrsd stocks, which would be expected to reduce the vigor of the stock, may have functioned as a selective force, favoring mutations that increased female receptivity. Possible consequences of selection favoring the development of differential female receptivity on speciation are discussed.     

Prenatal stress eliminates differential maternal attention to male offspring in Norway rats

Maternal licking behavior was observed in 20 Long-Evans rat dams on two consecutive days. Stimulus pups were male and female foster pups from dams that were either housed with 5 adult males during the last trimester of pregnancy (stressed) or housed alone (unstressed). Unstressed male pups received significantly more maternal licking than their female siblings, but prenatally stressed males and females received similar levels of maternal licking, comparable to that directed to unstressed females. In a second study, urine collected from prenatally stressed male pups elicited significantly less investigation from dams in a choice test than urine from age-matched unstressed males. It is concluded that the chemosignals which stimulate dams normally to provide more maternal attention to male than female neonates are deficient in prenatally stressed males. The results raise the possibility that differential maternal care may mediate some effects of prenatal stress on behavioral development in males.