Alternative mating tactics in the yellow dung fly: resolving mechanisms of small-male advantage off pasture.

Recent work suggests that the yellow dung fly mating system may include alternative patroller-competitor mating tactics in which large males compete for gravid females on dung, whereas small, non-competitive males search for females at foraging sites. Small males obtain most matings off pasture, yet the behavioural mechanism(s) giving rise to this pattern are unknown. We investigated the male and female behaviours that determine mating success in this environment by conducting field mating experiments and found small males to benefit from several attributes specific to the off-pasture mating environment. First, small males from foraging sites exhibited higher mating propensity, indicating that large males away from dung may be depleted of energy and/or sperm. Second, small males were more discriminating, being significantly less likely to attempt with non-gravid females, which are absent on dung but common off pasture. Third, non-gravid females were generally more likely to actively struggle and reject mating attempts; however, such behaviours occurred disproportionately more often with large males. Female Scathophaga stercoraria thus appear to preferentially mate with small males when off pasture. These findings challenge assumptions about male-female interactions in systems with alternative mating tactics and reveal hidden processes that may influence selection patterns in the field.

Resolving mechanisms of short-term competitive fertilization success in the red flour beetle.

Postcopulatory sexual selection occurs when sperm from multiple males occupy a female's reproductive tract at the same time and is expected to generate strong selection pressures on traits related to competitive fertilization success. However, knowledge of competitive fertilization success mechanisms and characters targeted by resulting selection is limited, partially due to the difficulty of discriminating among sperm from different males within the female reproductive tract. Here, we resolved mechanisms of competitive fertilization success in the promiscuous flour beetle Tribolium castaneum. Through creation of transgenic lines with fluorescent-tagged sperm heads, we followed the fate of focal male sperm in female reproductive tracts while tracking paternity across numerous rematings. Our results indicate that a given male's sperm persist and fertilize eggs through at least seven rematings. Additionally, the proportion of a male's sperm in the bursa (the site of spermatophore deposition), which is influenced by both timing of female's ejecting excess sperm and male size, significantly predicted paternity share in the 24h following a mating. Contrary to expectation, proportional representation of sperm within the female's specialized sperm-storage organ did not significantly predict paternity, though spermathecal sperm may play a role in fertilization when females do not have access to mates for longer time periods. We address the adaptive significance of the identified reproductive mechanisms in the context of T. castaneum's unique mating system and ecology.

Small school-based effectiveness trials increase vegetable and fruit consumption among youth.

This article profiles a research initiative of state health agency-initiated 5 A Day school-based interventions. Four of the seven projects reviewed had significant results, with an average effect size of 0.4 servings of vegetables and fruit. Results are comparable with the larger-scale, well-controlled, and more costly 5 A Day For Better Health efficacy trials. These comparable findings underscore the value of assessing effectiveness of interventions in real-world settings to potentially enable wide-scale implementation of tested strategies. These small effectiveness trials show that school-based interventions are feasible to implement using current and effective strategies, and may facilitate translation of health promotion research to practice. The projects fostered valuable research/practice partnerships at the community level. Limitations across studies included heterogeneity in research methods, participant attrition, and variability in reporting data. Further research is needed to develop standardized, cost-effective dietary assessment methodology for viable dissemination research in community settings.

Associations between perceived parent behaviors and middle school student fruit and vegetable consumption.

OBJECTIVE: To examine whether (1) student perceptions of parent behaviors explain variations in fruit and vegetable consumption, (2) self-efficacy mediates this relationship, and (3) perceived home fruit and vegetable availability moderates this relationship. DESIGN: A cross-sectional survey. SETTING: Classrooms in 3 middle schools in 2 northeast Georgia counties. PARTICIPANTS: 366 middle school students. The response and participation rates were 59% and 56%, respectively. VARIABLES MEASURED: Perceived authoritative parenting, perceived parent control, perceived parent modeling, perceived parent support, self-efficacy, perceived fruit and vegetable availability, and fruit and vegetable consumption. ANALYSIS: Hierarchical multiple regression; P <.05. RESULTS: Perceived parent modeling, perceived parent support, self-efficacy, and perceived fruit and vegetable availability were significant predictors of fruit and vegetable consumption. The relationship between perceived parent support and fruit and vegetable consumption was mediated by self-efficacy. The relationship between fruit and vegetable consumption and both perceived parent modeling and support was moderated by perceived fruit and vegetable availability. CONCLUSIONS AND IMPLICATIONS: Parents appear to moderately influence middle school student fruit and vegetable consumption. Educators might focus on improving home fruit and vegetable availability and student self-efficacy, as well as parent support and modeling. The level of availability might indicate where efforts should focus for enhancing parent behaviors.

Development of the Student Attitudes Toward School Safety Measures (SATSSM) instrument.

The Student Attitudes Toward School Safety Measures (SATSSM) instrument was developed as a new tool to assess high school students' attitudes towards school safety promotion methods. A theory-based pool of statements was scaled using Thurstone's equal appearing interval method by 186 student judges to yield a 30-item instrument. The draft version was operationalized into a 5-point, Likert scale format, using a new sample of 182 students. Exploratory factor analysis suggested three factors: mediation, surveillance, and searching methods. The SATSSM was reduced to six items for each scale with a five-item social desirability scale added, and piloted with 66 new students. Final administration of the SATSSM to 166 new students yielded scale and overall internal consistencies exceeding .80 with low interscale correlations. A simultaneously administered questionnaire measuring perceptions of school safety suggested students possessed increased awareness of school violence, but they believed improving school safety is beyond their school's control.

No inbreeding depression in sperm storage ability or offspring viability in Drosophila melanogaster females.

Mating between relatives usually decreases genetic quality of progeny as deleterious recessive alleles are expressed in inbred individuals. Inbreeding degrades sperm traits but its effects on sperm storage and fate within females are currently unknown. We quantified the relationship between the degrees of inbreeding relevant to natural populations (f=0, 0.25 and 0.50) and the number of sperm inseminated and stored, sperm swimming speed, long-term sperm viability while in storage, pattern of sperm precedence, mating latency, and offspring viability of female Drosophila melanogaster. The use of transgenic flies that have either red or green fluorescent sperm heads allowed us to distinguish two ejaculates in the female reproductive tract and facilitated quantification of sperm storage and use traits. We found no inbreeding depression in either long- or short-term sperm storage ability. The most inbred females exhibited significantly longer mating latency, which could be explained by males preferring to mate with outbred females. On the other hand, as no evidence for cryptic male choice in the form of ejaculate tailoring of sperm number was found, the most inbred females might just be less eager to mate. We also found no evidence that the degree of maternal inbreeding influenced offspring viability. Comparison with a contemporaneous study of male inbreeding consequences for ejaculate quality suggests that inbreeding depression is more severe in males than in females in our study population.

Inbreeding reveals mode of past selection on male reproductive characters in Drosophila melanogaster.

Directional dominance is a prerequisite of inbreeding depression. Directionality arises when selection drives alleles that increase fitness to fixation and eliminates dominant deleterious alleles, while deleterious recessives are hidden from it and maintained at low frequencies. Traits under directional selection (i.e., fitness traits) are expected to show directional dominance and therefore an increased susceptibility to inbreeding depression. In contrast, traits under stabilizing selection or weakly linked to fitness are predicted to exhibit little-to-no inbreeding depression. Here, we quantify the extent of inbreeding depression in a range of male reproductive characters and then infer the mode of past selection on them. The use of transgenic populations of Drosophila melanogaster with red or green fluorescent-tagged sperm heads permitted in vivo discrimination of sperm from competing males and quantification of characteristics of ejaculate composition, performance, and fate. We found that male attractiveness (mating latency) and competitive fertilization success (P2) both show some inbreeding depression, suggesting they may have been under directional selection, whereas sperm length showed no inbreeding depression suggesting a history of stabilizing selection. However, despite having measured several sperm quality and quantity traits, our data did not allow us to discern the mechanism underlying the lowered competitive fertilization success of inbred (f = 0.50) males.

Mecamylamine and ethanol preference in healthy volunteers.

BACKGROUND: Recent evidence suggests that some of the behavioral effects of alcohol may be mediated through actions on nicotinic acetylcholine receptors. Mecamylamine, a nicotinic acetylcholine receptor antagonist, reduces alcohol preference and consumption in alcohol-preferring rats, and in humans, mecamylamine dampens some of the subjective, or mood-altering, effects of alcohol. This experiment was designed to investigate the effects of mecamylamine on consumption of alcohol in healthy social drinkers. METHODS: Healthy volunteers (12 men, 12 women) participated in a choice procedure in which they chose between an alcoholic beverage and money (low, medium, or high amounts) after pretreatment with mecamylamine (7.5 or 15 mg) or placebo. Outcome measures were the number of alcoholic beverages consumed and the subjective effects of alcohol. RESULTS: Mecamylamine (15 mg) decreased blood alcohol levels (BALs) after a small fixed dose of alcohol (0.2 g/kg). Even when the lower BALs were taken into account, mecamylamine reduced ratings of stimulation after alcohol (Addiction Research Center Inventory A scale). Mecamylamine did not significantly reduce choice for alcohol versus money. However, there was a tendency for the drug to decrease alcohol choice among participants who reported the greatest stimulant-like effects from alcohol. CONCLUSION: These results provide only limited support for the idea that nicotinic acetylcholine receptors are involved in the rewarding effects of alcohol.