Pterin-based ornamental coloration predicts yolk antioxidant levels in female striped plateau lizards (Sceloporus virgatus)

1. Maternal investment in egg quality can have important consequences for offspring fitness. For example, yolk antioxidants can affect embryonic development as well as juvenile and adult phenotype. Thus, females may be selected to advertise their yolk antioxidant deposition to discriminatory males via ornamental signals, perhaps depending on the reproductive costs associated with signal production. 2. Female striped plateau lizards (Sceloporus virgatus) develop pterin-based orange colour patches during the reproductive season that influence male behaviour and that are positively associated with the phenotypic quality of the female and her offspring. Here, we assessed one potential developmental mechanism underlying the relationship between offspring quality and female ornamentation in S. virgatus, by examining the relationship between ornament expression and yolk antioxidant levels. 3. As expected, concentrations of the yolk antioxidants vitamin A, vitamin E and carotenoids (lutein and zeaxanthin) were strongly positively intercorrelated. Eggs from larger clutches had fewer antioxidants than eggs from smaller clutches, suggesting that females may be limited in antioxidant availability or use. Fertilized and unfertilized eggs did not differ in yolk antioxidant levels. 4. The size of a female's ornament was positively related to both the concentration and total amount of yolk antioxidants, and ornament colour was positively related to yolk antioxidant concentration. Thus, in S. virgatus, female ornaments may advertise egg quality. In addition, these data suggest that more ornamented females may produce higher-quality offspring, in part because their eggs contain more antioxidants. As the colour ornament of interest is derived from pterins, not carotenoids, direct resource trade-offs between ornaments and eggs may be eliminated, reducing reproductive costs associated with signalling. 5. This is the first example of a positive relationship between female ornamentation and yolk antioxidants in reptiles and may indicate the general importance of these patterns in oviparous vertebrates.     

Pteridine, not carotenoid, pigments underlie the female-specific orange ornament of striped plateau lizards (Sceloporus virgatus)

Indicator models of sexual selection suggest that signal honesty is maintained via costs of ornament expression. Carotenoid-based visual signals are a well-studied example, as carotenoids may be environmentally limited and impact signaler health. However, not all bright yellow, orange and red ornaments found in vertebrates are carotenoid-based; pteridine pigments may also produce these colors. We examine the contribution of carotenoid and pteridine pigments to the orange reproductive color of female striped plateau lizards (Sceloporus virgatus). This color ornament reliably indicates female mate quality, yet costs maintaining signal honesty are currently unknown. Dietary carotenoid manipulations did not affect orange color, and orange skin differed from surrounding white skin in drosopterin, not carotenoid, content. Further, orange color positively correlated with drosopterin, not carotenoid, concentration. Drosopterin-based female ornaments avoid the direct trade-offs of using carotenoids for ornament production vs egg production, thus may relax counter-selection against color ornament exaggeration in females. Direct experimentation is needed to determine the actual costs of pteridine-based ornaments. Like carotenoids, pteridines influence important biological processes, including immune and antioxidant function; predation and social costs may also be relevant.     

Female-specific color is a signal of quality in the striped plateau lizard (Sceloporus virgatus)

Recent theoretical and empirical studies confirm that male matechoice and/or female–female mate competition can be expressedin the absence of sex-role reversal. Such reproductive patternsmay select for the evolution of female traits that indicatefemale phenotypic or genotypic quality among non–role-reversedspecies. Although attention to the evolution and function offemale ornaments is increasing, additional focus is needed onfemale-specific ornaments (those not expressed in conspecificmales) and on nonavian systems in order to gain a broad understandingof how selection acts directly on ornamentation of female animals.In the striped plateau lizard, Sceloporus virgatus, only femalesdevelop orange throat patches during the reproductive season.The color peaks in expression near the time of ovulation andappears to stimulate male courtship. Here, I examine whetherthis female-specific ornament can be used by males to reliablyassess female phenotypic quality. Using multivariate regressionanalyses, I show that the area of the orange color patch predictsbody condition and mite load, the chroma (i.e., saturation)of the color patch predicts body size, and both patch area andchroma reliably predict average egg mass. Thus, female reproductivecolor may function as a condition-dependent signal, indicatingphenotypic quality to potential mates.     

Optimal escape theory predicts escape behaviors beyond flight initiation distance： risk assessment and escape by striped plateau lizards Sceloporus virgatus

Escape theory predicts that flight initiation distance (FID=distance between predator and prey when escape begins) is longer when risk is greater and shorter when escape is more costly. A few tests suggest that escape theory applies to distance fled. Escape models have not addressed stochastic variables, such as probability of fleeing and of entering refuge, but their economic logic might be applicable. Experiments on several risk factors in the lizard Sceloporus virgatus confirmed all predictions for the above escape variables. FID was greater when approach was faster and more direct, for lizards on ground than on trees, for lizards rarely exposed to humans, for the second of two approaches, and when the predator turned toward lizards rather than away. Lizards fled further during rapid and second consecutive approaches. They were more likely to flee when approached directly, when a predator turned toward them, and during second approaches. They were more likely to enter refuge when approached rapidly. A novel finding is that perch height in trees was unrelated to FID because lizards escaped by moving out of sight, then moving up or down unpredictably. These findings add to a growing body of evidence supporting predictions of escape theory for FID and distance fled. They show that two probabilistic aspects of escape are predictable based on relative predation risk levels. Because individuals differ in boldness, the assessed optimal FID and threshold risks for fleeing and entering refuge are exceeded for an increasing proportion of individuals as risk increases[Current Zoology 55(2):123-131,2009].     

Diurnal variations of androgens in sexually mature male Bolivian squirrel monkeys (Saimiri sciureus) during the breeding season

To assess diurnal fluctuations of serum androgens and cortisol in adult male Bolivian squirrel monkeys, these steroids were measured at predetermined times (0300, 0900, and 2300 hours) during two separate 24-hour periods in the breeding season (January 1983 and late November 1983). A significant diurnal change in serum cortisol was noted, with a nadir of 99.9 ± 11.9 μg/dl (x? ± SEM) at 2300 hours and a peak of 168.9 ± 7.8 μg/dl at 0900 hours. Conversely, a nadir in serum testosterone was noted at 0900 hours (117 ± 26.5 ng/ml) increasing to a peak of 328.5 ± 57.9 ng/ml at 0300 hours. Serum androstenedione and dehydroepiandrosterone followed a pattern similar to testosterone, with a serum androstenedione (176.4 ± 34.9 ng/ml) and dehydroepiandrosterone (11.7 + 1.8 ng/ml) nadir at 0900 hours and a plasma androstenedione (494.5 ± 55.4 ng/ml) and dehydroepiandrosterone (32.5 ± 4.1 ng/ml) peak at 0300 hours. Parallel changes of testosterone, androstenedione, and dehydroepiandrosterone suggest a significant contribution of all three androgens from a common site, the testes. In contrast to old world primates and humans, serum androstenedione levels exceeded serum testosterone levels in this species.     

The influence of competitor density on space use in juvenile striped plateau lizards (Sceloporus virgatus)

To investigate the role of competitor density in influencing space use patterns of juvenile striped plateau lizards (Sceloporus virgatus), a density manipulation experiment was conducted within large (800 m²) field enclosures treated with low (20) and high (60) densities of hatchlings. Enclosures were monitored for 10 months, after which the experiment was replicated. Home range and core area sizes after release of lizards and initial establishment in the fall were significantly reduced in the high-density treatments; fall home range shape, measured as the perimeter-to-area ratio, was significantly reduced in low-density treatments; no significant differences were detected between treatments in core area shape or overlap. During the spring/early summer activity season after the lizard's first winter, no significant differences between density treatments were detected for any of these variables, as enclosure densities had converged between treatments. Individuals in high-density enclosures had increased their space use as competitor density had declined. These results illustrate that competitor density has significant influence on space use by juvenile lizards.     

中国石龙子繁殖季节血浆性类固醇激素水平的变化

本文研究了中国石龙子繁殖季节中性腺变化与血浆性类固醇激素水平波动间的相互关系。结果表明：雌性中国石龙子卵黄生成需要雌二醇(17β-estradiol,E2)的刺激。体现在卵巢重量于4月底至5月中旬间达峰值,血浆E2水平于3月底至最高值,此后显著回落,并于排卵前再次回升;血浆孕酮(progesterone,P)的生理功能在于输卵管卵的维持、促进胚胎发育和卵壳的形成。从3月中旬至4月底间,血浆P水平在基础值附近波动。5月中旬,随动物的排卵,血浆P水平迅速上升,至该月底达最高值,于产卵后迅速下降;E2随P的上升而下降,两者呈反向变动。雄性血浆睾酮(testosterone,T)水平与生精作用、维持攻击、求偶及交配行为密切相关。血浆T水平于动物出眠后呈现显著的上升趋势,并于4月中旬达峰值。5月中旬后,随睾丸的萎缩,血浆T水平也缓慢下降,至6月底达最低值。     

Plasma concentrations of progesterone in female red deer (Cervus elaphus) during the breeding season, pregnancy and anoestrus

Concentrations of progesterone in peripheral plasma of red deer hinds were basal (less than 1 ng/ml) during lactation/seasonal anoestrus, but increased abruptly at the onset of the breeding season. Lactating hinds (N = 19) started ovarian cycles 10 days later (P less than 0.01) and conceived 16 days later (P less than 0.001) than did 13 weaned hinds. There was no evidence, from plasma progesterone values, of silent oestrus at the start of the season. Progestagen/PMSG treatment induced early ovulations in 8 anoestrous hinds but fertility was low, only 2 conceiving and giving birth. Pregnant hinds (N = 42) had high plasma concentrations of progesterone (mean 3-5 ng/ml) which declined just before parturition.     

Testosterone inhibits growth in juvenile male eastern fence lizards (Sceloporus undulatus): implications for energy allocation and sexual size dimorphism

In the eastern fence lizard, Sceloporus undulatus, female-larger sexual size dimorphism develops because yearling females grow faster than males before first reproduction. This sexual growth divergence coincides with maturational increases in male aggression, movement, and ventral coloration, all of which are influenced by the sex steroid testosterone (T). These observations suggest that male growth may be constrained by energetic costs of activity and implicate T as a physiological regulator of this potential trade-off. To test this hypothesis, we used surgical castration and subsequent administration of exogenous T to alter the physiological and behavioral phenotypes of field-active males during the period of sexual growth divergence. As predicted, T inhibited male growth, while castration promoted long-term growth. Males treated with T also exhibited increased daily activity period, movement, and home range area. Food consumption did not differ among male treatments or sexes, suggesting that the inhibitory effects of T on growth are mediated by patterns of energy allocation rather than acquisition. On the basis of estimates derived from published data, we conclude that the energetic cost of increased daily activity period following T manipulation is sufficient to explain most (79%) of the associated reduction in growth. Further, growth may have been constrained by additional energetic costs of increased ectoparasite load following T manipulation. Similar studies of the proximate behavioral, ecological, and physiological mechanisms involved in growth regulation should greatly improve our understanding of sexual size dimorphism.     

Vocalisation and its association with androgens and corticosterone in a night frog (Nyctibatrachus humayuni) with unique breeding behaviour

In anurans, vocalisation is used to communicate within and between the sexes during reproduction. Knowledge of vocal repertoire and its diversity is essential in understanding its significance in sexual selection. In this context, we studied the vocal behaviour of Nyctibatrachus humayuni and quantified the urinary metabolites of androgens and corticosterone to understand the associations among hormones, body condition index and vocalisation. Our results show that males of N. humayuni produce an amplitude‐modulated call consisting of a train of pulses. Interestingly, a high degree of inter‐individual variation was observed in the call parameters. The dominant frequency and pulse interval were negatively correlated with male body size, whereas pulse duration and pulse duty cycle were positively correlated with it. Dominant frequency was negatively correlated with androgens and corticosterone, whereas pulse interval was negatively correlated with corticosterone. Further, pulse duty cycle, pulse duration and pulses per call were positively associated with corticosterone. Surprisingly, none of the acoustic parameters was associated with male body temperature and body condition. A significant variation was evident in the vocal effort, dominant frequency and amplitude of advertisement calls produced under different social situations. Calls produced during territory establishment had lower dominant frequency but higher vocal effort, whereas those produced during courtship had higher amplitude and vocal effort than the calls produced in the absence of a competitor/female. Our results suggest that greater inter‐male variability in the advertisement call of N. humayuni could be important in female choice as it may help females to assess the quality of a male. Further, androgens and corticosterone could be important in modulating crucial parameters of the advertisement call.     

Changes in free and total plasma cortisol levels in juvenile haddock (Melanogrammus aeglefinus) exposed to long-term handling stress

We measured changes in free and total plasma cortisol levels, plasma glucose, gill hsp70 levels, and growth in haddock (Melanogrammus aeglefinus) subjected to a long-term handling stress (15 s out of water, each day, for 4 weeks), and the effect of this long-term stress on the ability of haddock to respond to an acute stressor. The acute stressor was a single handling stress, and fish were sampled at 1, 6, and 12 h post-stress. During the long-term stress study, free and total plasma cortisol levels increased significantly (10-fold) in the stressed group after the second week. However, the percentage of free cortisol was already significantly elevated by the first week (control 17%, stressed 55%), and remained high during the second week (control 35% and stressed 65%). After 3 and 4 weeks of handling, both free and total cortisol declined in stressed fish to levels that were not significantly different from pre-stress values. Control fish grew significantly more than stressed fish (by 32% and 18%, respectively) over the 4 week study, and condition factor only increased in control fish. Although fish from the control group showed elevated total plasma cortisol levels (to 47 ng mL(-1)) 1 h after the acute stress, and the levels in stressed fish were comparable to those for the control fish, no significant increase in plasma cortisol was measured in the group subjected to the long-term stress. Free plasma cortisol levels did not increase significantly in either group following the acute stress. However, free plasma cortisol levels were significantly higher in long-term stress group, as compared with the control group, at 6 h post-stress. Plasma glucose and gill hsp70 levels were not altered by either the long-term stress or acute stressor. Our data indicate that cortisol (free and total), but not glucose or hsp70, appears to be adequate to assess short- and long-term stress in haddock.     

Effect of prenatal androgens on click-evoked otoacoustic emissions in male and female sheep (Ovis aries)

Otoacoustic emissions (OAEs) were measured in male and female Suffolk sheep (Ovis aries). Some sheep had been administered androgens or estrogens during prenatal development, some were gonadectomized after birth, and some were allowed to develop normally. As previously reported for spotted hyenas, gonadectomy did not alter the OAEs for either sex; accordingly, the untreated/intact and the untreated/gonadectomized animals were pooled to form the control groups. The click-evoked otoacoustic emissions (CEOAEs) exhibited by the female control group (N = 12) were slightly stronger (effect size = 0.42) than those in the male control group (N = 15), which is the same direction of effect reported for humans and rhesus monkeys. Females administered testosterone prenatally (N = 16) had substantially weaker (masculinized) CEOAEs than control females (effect size = 1.15). Both of these outcomes are in accord with the idea that prenatal exposure to androgens weakens the cochlear mechanisms that underlie the production of OAEs. The CEOAEs of males administered testosterone prenatally (N = 5) were not different from those of control males, an outcome also seen in similarly treated rhesus monkeys. Males administered dihydrotestosterone (DHT) prenatally (N = 3) had slightly stronger (hypo-masculinized) CEOAEs than control males. No spontaneous otoacoustic emissions (SOAEs) were found in any ears, a common finding in non-human species. To our knowledge, this is the first ruminant species measured for OAEs.     

The effects of indomethacin on plasma LH levels in female and male deermice ( )

The purpose of this investigation was to determine (1) the approximate time of the preovulatory LH rise in cyclic deermice, (2) the effect of indomethacin administration on plasma LH levels during the expected preovulatory LH rise, and (3) the effect of indomethacin administration on plasma LH levels in castrated male deermice. The data indicate that the preovulatory LH rise occurred at about 2200 h on proestrus and that indomethacin pretreatment significantly reduced plasma LH levels during that time. In addition, indomethacin significantly reduced plasma LH levels in castrated male deermice. We conclude that plasma LH levels remain low throughout the estrous cycle with the exception of the preovulatory “surge”, that plasma LH levels in deermice are comparable to those reported for the rat, and that indomethacin pretreatment reduced plasma LH levels during periods when they were expected to be elevated (in castrated males and during the expected preovulatory LH rise in female deermice). The data are consistent with the hypothesis that the effect of indomethacin on plasma LH levels is due to an inhibitory effect on hypothalamic PG biosynthesis.     

The interplay between natural and sexual selection in the evolution of sexual size dimorphism in Sceloporus lizards (Squamata: Phrynosomatidae)

Sexual size dimorphism (SSD) evolves because body size is usually related to reproductive success through different pathways in females and males. Female body size is strongly correlated with fecundity, while in males, body size is correlated with mating success. In many lizard species, males are larger than females, whereas in others, females are the larger sex, suggesting that selection on fecundity has been stronger than sexual selection on males. As placental development or egg retention requires more space within the abdominal cavity, it has been suggested that females of viviparous lizards have larger abdomens or body size than their oviparous relatives. Thus, it would be expected that females of viviparous species attain larger sizes than their oviparous relatives, generating more biased patterns of SSD. We test these predictions using lizards of the genus Sceloporus. After controlling for phylogenetic effects, our results confirm a strong relationship between female body size and fecundity, suggesting that selection for higher fecundity has had a main role in the evolution of female body size. However, oviparous and viviparous females exhibit similar sizes and allometric relationships. Even though there is a strong effect of body size on female fecundity, once phylogenetic effects are considered, we find that the slope of male on female body size is significantly larger than one, providing evidence of greater evolutionary divergence of male body size. These results suggest that the relative impact of sexual selection acting on males has been stronger than fecundity selection acting on females within Sceloporus lizards.     

Seasonal changes in testicular contents and plasma concentrations of androgens in the desert gerbil (Gerbillus gerbillus)

Gerbils were caught in the Béni-Abbès area (Algeria). Testicular endocrine activity was highest in spring (testicular wt 298 +/- 10 mg; seminal vesicle wt 603 +/- 62 mg; testicular testosterone and androstenedione content 9.2 +/- 1.7 and 0.5 +/- 0.1 ng/testis; plasma testosterone 832 +/- 200 pg/ml). Values decreased in summer, were lowest in late summer and in autumn (84 +/- 17 mg; 40 +/- 14 mg; 0.20 +/- 0.06 and 0.02 +/- 0.01 ng/testis; 228 +/- 54 pg/ml, respectively) and increased again in winter (December-January). The onset of testicular endocrine activity was concomitant with the lowest temperatures and the shortest photoperiod; it increased when temperatures and daylength were increasing and began to decline when temperatures and photoperiod were still maximal. These seasonal changes in the endocrine activity of the testis of the gerbil differ from those of the sand rat inhabiting the same area.