Sexual selections in the northern fall field cricket, Gryllus pennsylvanicus: a manipulation of the adult sex ratio

The operational sex ratio has long been considered an important constraint on the structure of mating systems. The effects of an experimentally manipulated sex ratio on mating behavior and selection were investigated in a polygynous species, Gryllus pennsylvanicus, where the potential exists for spatial/temporal fluctuations in sex ratio of field populations. Four different sex ratios (males: females, 5:0, 5:2, 5:5, 5:10) were investigated. Observations were conducted in late summer over two field seasons, from 2400 h , to 1000 h EST. Several male characters thought to be associated with male reproduc.tive success were studied: calling duration, searching distance, weight, fighting behavior, courtship frequency, and mating success. Variance in male mating success was used as the indicator for the opportunity for sexual selection. Total selection was estimated as the univariate regression coefficient between relative fitness and the character of interest, while direct selection was estimated as standardized partial regression coefficients generated from a multiple regression of relative fitness on each character. The opportunity for sexual selection was highest at 5:2 and lowest at 5:10. The frequency of fighting behavior was highest at 5:2 and 5:5. Fighting ability (% wins) was determined to be an important correlate of male body weight. Direct selection for increased male body weight was detected at 5:2, while total selection for body weight was seen at 5:5. Selection on male body weight was not detected at 5: 10. Calling duration decreased as sex ratio became more female-biased. Total and direct selection were detected for increased calling at 5:2, only total selection for calling was seen at 5:5, whereas direct selection against calling was detected at 5: 10. Searching distance also decreased as sex ratio became more female-biased, however no form of selection was detected for searching at any of the sex ratios. Data are discussed in terms of sexual selection on male reproductive tactics, the mating system and maintenance of genetic variation in male reproductive behavior.

Locomotor sensitization and conditioned place preference for amphetamine in late adolescent and adult male and female rats /

reports, the players did not show an anticipatory rise in either Cortisol or testosterone prior to competition. In addition to the effects of status outcome on hormonal levels, it was also found that these hormonal responses were specific to competition. The athletes in the current study did not demonstrate any hormonal responses to the practice sessions. Last, there were significant differences in pre-game testosterone as well as in selfconfidence, cognitive, and somatic anxiety levels depending on the location at which the status contest took place. Pre-game testosterone and self-confidence levels were significantly higher prior to games played in the home venue. In contrast, pre-game somatic and cognitive anxiety levels were significantly higher prior to games played in the away venue. The current findings add to the developing literature on the relationship between hormones and competition. This was the first study to detect a moderating effect of status outcome on testosterone responses in a team sport. Furthermore, this was also the first study in humans to demonstrate that post-contest Cortisol levels were significantly higher after a loss of status. Last, the current study also adds to the sport psychology literature by demonstrating that pre-game psychological variables differ depending on where the status contest is being held: higher self-confidence at home and higher somatic and cognitive anxiety away. Taken together, the results from the current thesis may have important practical relevance to coaches, trainers and sport psychologists who are always trying to find ways to maximize performance. the cycle. The sex-specific age differences in locomotor responses to amphetamine are not due to gonadal immaturity, as females are cycling at this stage of adolescence. However, age differences may reflect the ongoing maturation of the neural substrates that that are involved in locomotor sensitizing, but not rewarding effects of amphetamine.

Autonomic regulation and blood pressure in children

Vagal baroreflex sensitivity (BRS) is a measure of short term blood pressure (BP) regulation through alterations in heart rate. Low BRS reflects impaired autonomic system regulation and has been found to be a surrogate marker for cardiovascular health. In particular, it has found to be associated with the pathogenesis of adult hypertension. However, only limited information exists as to the negative consequences of childhood BP on baroreflex function. The objective of this study was to investigate BRS in children with 2 different BP profiles while controlling for the effects of age, maturation, sex, and body composition. A preliminary subsample of 11-14 year-old children from the HBEAT (Heart Behavioural Environmental Assessment Team) Study was selected. The children were divided into 2 BP groups; high BP (HBP; 2:95tl1 percentile, n=21) and normal BP (NBP; <90th percentile, n=85). Following an initial 15 minutes of supine rest, 5 minutes of continuous beat-to-beat BP (Finapres) and RR interval (RRI) were recorded (standard ECG). Spectral indices were computed using Fast Fourier Transform and transfer function analysis was used to compute BRS. High frequency (HF) and low frequency (LF) power spectral areas were set to 0.15-0.4 Hz and 0.04-0.15 Hz, respectively. Body composition was measured using body mass index. After adjusting for body composition, maturation, age and sex ANCOV A results were as follows; LF and HF BRS, LF and HF RRI, and RRI total power were lower in the HBP versus NBP participants (p<0.05). As well, LF IHF SBP ratio was significantly higher in the HBP compared to the NBP group (p<0.05). The regression coefficients (unstandardized B) indicated that in changing groups (NBP to HBP) LF and HF BRS decreases by 4.04 and 6.18 ms/mmHg, respectively. Thus, as BP increases, BRS decreases. These data suggest that changes in autonomic activity occur in children who have HBP, regardless of age, sex, maturation, and body composition. Thus, despite their young age and relatively short amount of time having high BP compared with adults, these children are already demonstrating poor BP regulation and reduced cardiovagal activity. Given that childhood BP is associated with hypertension in adulthood, there is a growing concern in regards to the current cardiovascular health of our children and future adults.