Leonor Hernández-López

Endocrine changes in male stumptailed macaques (Macaca arctoides) as a response to odor stimulation with vaginal secretions.

In mammalian species, social chemosignals are important in modulating endocrine reproductive functions. In nonhuman primates, previous studies have described a high frequency of mounting behavior by females in the follicular and periovulatory phases of the menstrual cycle. Stumptailed macaque females do not signal receptivity by means of sexual swellings, as do others macaques, therefore providing a good model in which to study chemical signaling of reproductive status. We exposed anesthetized stumptailed males to vaginal secretions of either late follicular or menses phase or to saline solution to determine the endocrine changes promoting male sexual behavior. In males exposed to follicular secretions, plasma testosterone concentrations were sustained up to 120 min after exposure. Such an effect was not observed in animals exposed to menses or saline odor sources. A luteinizing hormone surge, occurring 30 minutes after exposure to late follicular phase secretion swabs, preceded this sustained testosterone effect. The fact that late follicular scents induce sustained testosterone concentrations provides support to the idea that stumptailed males draw information concerning female reproductive status from the females vaginal odor.

Changes in Men’s Salivary Testosterone and Cortisol Levels, and in Sexual Desire after Smelling Female Axillary and Vulvar Scents

Several studies have shown that a woman’s vaginal or axillary odors convey information on her attractivity. Yet, whether such scents induce psychoneuroendocrinological changes in perceivers is still controversial. We studied if smelling axillary and vulvar odors collected in the periovulatory and late luteal phases of young women modify salivary testosterone and cortisol levels, as well as sexual desire in men. Forty-five women and 115 men, all of them college students and unacquainted with each other, participated in the study. Female odors were collected on pads affixed to the axilla and on panty protectors both worn the entire night before experiments. Men provided five saliva samples, a basal one before the smelling procedure, and four more 15, 30, 60, and 75 min after exposure to odors. Immediately after smelling the odor source, men answered a questionnaire rating hedonic qualities of scents, and after providing the last saliva sample they answered questionnaire on sexual desire. We found that periovulatory axillary and vulvar odors increased testosterone and cortisol levels, with vulvar scents producing a more prolonged effect. Luteal axilla odors decreased testosterone and cortisol levels, while luteal vulva odors increased cortisol. Periovulatory axilla and vulva scents accounted for a general increase of interest in sex. These odors were also rated as more pleasant and familiar, while luteal vulvar odors were perceived as intense and unpleasant.

Male-Induced Sociosexual Behavior by Vaginal Secretions in Macaca arctoides

Odor communication in Old World monkeys and apes is controversial, because most females have evolved visual and behavioral cues to signal fertility, e.g., sexual swellings. Female stump-tailed macaques (Macaca arctoides) do not have swellings, and mediation of chemical communication likely occurs because males engage in sexual behavior mostly throughout the periovulatory phase of the menstrual cycle. We tested whether vaginal secretions from different cycle phases, with saline solution as a control, promote changes in the frequency of male genital exploration, copulation, and coercive behavior toward females different from the donors, while female donors were apart from the group. Males explored more female genitals when exposed to follicular, periovulatory, and early luteal secretions in comparison to saline or menstrual or late luteal secretions. The increase in coercive behavior after exposure to follicular and periovulatory secretions most likely was a male response to the lack of cooperation of target females in engaging in copulation, as the latter were not receptive during the tests. The strength of male response to vaginal secretions varied significantly as a result of individual variability between donor females, yet the variability does not correlate either to dominance rank or to female age. Exploratory behavior of males correlates significantly with their social rank. Our results suggest that vaginal secretions are among the cues that male Macaca arctoides use to acknowledge the reproductive status of females in the absence of visual signals.

The menstrual cycle of the spider monkey (Ateles geoffroyi)

The ovarian cycles of four adult female spider monkeys (Ateles geoffroyi) were followed daily throughout 30 days by means of vaginal swabs and blood samplings. Cytological analyses of the vaginal swabs and radioimmunoassay determination of the daily levels of estradiol‐17β (E2) and progesterone (P4) were done in order to classify the kind of ovarian cycle of this species. Our results show that Ateles geoffroyi females display menstrual cycles of about 24 days on average. By comparison with the well‐known menstrual cycles of women, apes, and Old World monkeys, the four distinctive cytological phases (bleeding, follicular, periovulatory, and luteal) could be recognized; mid‐cycle E2 peaks followed by mid‐luteal increases of the same hormone were present in all four females. P4 levels were higher after the E2 peak, although both hormones were present throughout the cycles. Also, age‐dependent features, hormone profiles, and changes in menstrual phases lengths were detected. Am. J. Primatol. 44:183–195, 1998.

Comparison of the effects of Percoll and PureSperm on the common marmoset (Callithrix jacchus) semen

Abstract:  Density gradient centrifugation is a widely used technique for the separation of motile from non‐motile sperm, for the removal of contaminating agents such as bacteria and viruses, and for the removal of seminal plasma or cryoprotectant. In the choice of a density gradient medium for a new species, it is important to perform toxicity tests. The present study was carried out to evaluate the potential toxic effects of two silica‐based density gradient products (Percoll and PureSperm), on the sperm of the common marmoset. We assessed two different batches of Percoll (polyvinylpyrrolidone (PVP)‐coated colloidal silica particles) and one of PureSperm (saline‐coated colloidal silica suspension) by means of a computer‐aided sperm analysis on semen collected by vibrostimulation. The results showed that although some of the sperm patterns of movement and viability changed significantly over time, and provide a first description of marmoset sperm motility changes under capacitating conditions, there was no significant difference in the sperm treated with Percoll or PureSperm in comparison with the control. We conclude that simple exposure to either of these products does not have a negative effect on viability or motility of marmoset sperm.

Waist-to-Hip Ratio, but Not Body Mass Index, Is Associated with Testosterone and Estradiol Concentrations in Young Women

We studied if testosterone and estradiol concentrations are associated with specific female waist-to-hip ratios (WHRs) and body mass indices (BMIs). Participants were 187 young women from which waist, hips, weight, and height were measured. In addition, participants informed on which day of their menstrual cycle they were and provided a 6 mL saliva sample. Ninety-one of them were in the follicular phase and 96 in the luteal phase. Only in the fertile phase of the menstrual cycle we found a significant interaction between testosterone and estradiol affecting WHR (b ± s.e. = −0.000003 ± 0.000001;  t 94 = −2.12, adjusted R 2 = −0.008,  P = 0.03). Women with the highest levels of both hormones had the lowest WHRs, while women with low estradiol and high testosterone showed the highest WHRs. BMI significantly increased as testosterone increased in female in their nonfertile days.

Seasonality of LH, testosterone and sperm parameters in spider monkey males (Ateles geoffroyi)

There are no reported data on hormonal fluctuations in black‐handed spider monkey males. On previous research about the reproductive physiology of this monkey we have found that during the dry season females show ovulatory estrogen peaks and males present the best quality semen. As part of an ongoing research, in this study we assessed seasonal variations in the concentration of serum luteinizing hormone (LH) and testosterone (T) in three adult spider monkey males to corroborate the seasonal reproductive synchrony. At the same time sperm count and motility were evaluated to search for any correlation between those sperm parameters and hormonal concentrations. We took blood and semen samples (by electroejaculation) of anesthetized males throughout the rainy (June–September) and dry (October–May) months. Our results revealed that T and LH were higher throughout the dry season and there was a significant correlation between T concentration and sperm count. Although higher during the dry season, sperm motility tended to correlate with testosterone and LH levels. These results demonstrated that black‐handed spider monkeys have a tendency to show a seasonal pattern of reproduction being the dry season the most likely time to achieve fertilization. Am. J. Primatol. 71:427–431, 2009.

Testosterone, the progesterone/estradiol ratio, and female ratings of masculine facial fluctuating asymmetry for a long-term relationship

Idiosyncratic variation within the normal range of androgens levels in women account for significant variations in personality and behavior. We studied if testosterone introduces significant biases in womens perception of fluctuating symmetry of male faces suitability for a long-term relationship. Participants were 145 female college students asked to rate in a two-choice forced paradigm the attractiveness, suitability as a long-term partner, and economic success, fatherliness and fidelity of an asymmetric and a symmetric male face. Since our sample consists of random women interested in participating, whether for personal reasons or because they were paid to participate, we controlled for menstrual phase. All participants provided salivary samples to determine testosterone (T), estradiol (E2) and progesterone (P4) levels. When the P4/E2 was low and T low-to-normal, the symmetric face was rated as more attractive, and a desirable long-term partner, but these preferences changed to the opposite when P4/E2 was high. In high T women, neither face was rated as more attractive, independently from the P4/E2 ratio, but the asymmetric face was preferred as a long-term partner when conception risk was high, changing to prefer the symmetric face as the P4/E2 increased. The overall perception of male faces was that the symmetric face was more economical successful but a poor parent and highly unfaithful compared to the asymmetric face. A significant interaction between T and P4/E2 for ratings success of the asymmetric face suggests that high levels of feminine T might be related to inter-sexual competition when conception risk is high.

Aging-related reproductive decline in the male spider monkey (Ateles geoffroyi).

Background  It is unknown whether male black‐handed spider monkeys (Ateles geoffroyi) undergo a reproductive decline as they age. The purpose of this work was investigating whether serum testosterone and semen quality decrease with age in these primates as occur in other species.