Sexual Period Research Articles

Mating behavior and male mating success in wildAnastrepha Ludens (Diptera: Tephritidae) on a field-caged host tree

Mating behavior and factors affecting mating success of males were studied using wild Anastrepha ludens on a fieldcaged host tree. The most common courtship sequence had five components: (1) male calls from the underside of a leaf, (2) female arrives to the maleoccupied leaf, (3) male orients to female and stops calling, (4) one or both approach to a face-to-face position 1–3 cm apart, and (5) male mounts female after 1–2 s. Courtship behavior was almost identical to that of laboratoryculture flies observed previously under laboratory conditions. Most malefemale encounters occurred at a height of 1–2m, well inside the outer canopy of the tree. Differential mating success by males occurred. No male mated more than once per day, owing possibly to a very short sexual activity period. Factors favoring mating success of males were survival ability and tendency to join male aggregations and to fight other males. Thorax length and age (9–11 days difference) had no effects on male copulatory success. Overall win/loss percentage was not related to mating success because the males that were most successful at mating fought mostly among themselves, driving their win/loss percentage down. However, these successful males (at mating) won most of their fights against less successful males. Results confirmed a lek mating system: males aggregated, called, and defended territories; territories did not contain femalerequired resources; and females exercised mate choice, apparently through selection of sites within leks.

Aspects of pheromone biosynthesis in the Hessian fly, Mayetiola destructor (Say)

Virgin female Hessian flies biosynthesize sex phermone in a cyclical fashion throughout their lifetime. Pheromone titre is relatively high early in the photophase, coinciding with the period of sexual activity, and decreases to a low level some 8 h later in the photophase. Mating results in the cessation of pheromone biosynthesis. Injection of male abdomen extract into virgin females suggested that this is due to the transfer of a chemical factor from the male to the female during mating. Decapitated female Hessian flies did not biosynthesize sex pheromone. However, injection of female head extract into these decapitated females resulted in the biosynthesis of sex pheromone, indicating that pheromone biosynthesis is initiated by a factor located in the female head. Injection of synthetic pheromone biosynthesis activating neuropeptide of Heliothis zea into Hessian fly females also initiated some pheromone biosynthesis, and it is believed that this neuropeptide or a related neuropeptide is responsible for initiation of pheromone biosynthesis. Analysis of the fatty acyl groups present in the pheromone gland of virgin female Hessian flies revealed the unusual compound ( E)-9-dodecenoate. This compound may be an intermediate in the biosynthesis of the pheromone component (2S)-( E)-10-tridecen-2-yl acetate.

Suprachiasmatic Nucleus Lesions Abolish Photoperiod-Induced Changes in the Testis Function and GnRH Immunoreactivity in the Mink, a Short-Day Breeder

Testicular activity (testis volume and plasma testosterone) and immunoreactive GnRH hypothalamic system were examined after suprachiasmatic nucleus (SCN) lesion in the mink, a short-day breeding mammal, whose sexual activity is inhibited by day lengths exceeding 10 h. In animals maintained under a natural photoperiod, SCN destruction performed during the period of maximum sexual activity (February) was shown to have no effect on onset of the testicular inactive period which begins at the end of winter and continues through spring. On the other hand, while gonadal activity began again at the end of autumn in intact animals, minks that had undergone SCN destruction remained sexually inactive until the end of the experiment period (February). The SCN could thus be crucial to the onset of sexual activity triggered by the reduction of day length, whereas onset of sexual inactivity is a spontaneous phenomenon. This was confirmed in a second experiment demonstrating that a short photoperiod (4 L:20 D), highly gonadostimulatory in intact animals, had no effect on testicular activity after SCN destruction. An immunocytochemical study of the hypothalamic GnRH system (staining intensity and number of labeled perikarya and immunoreactive endings in the external layer of the median eminence) also showed consistent by very low rates of immunoreactivity and number of labeled perikarya and endings in operated animals.

Rhythmic occurrence of sexual behaviour and egg laying activity of Muscovy ducks

1. The existence of nychthemeral rhythms in the sexual behaviour of Muscovy ducks, kept under intensive husbandry conditions, was investigated. Studies were also carried out of the relationships between artificial insemination or natural mating times, oviposition time and female fertility. 2. Sexual activity (as measured by the number of complete matings observed) followed a trimodal pattern with peaks of activity in the second to third, 5th to 6th and 10th to 15th hours of the photoperiod. The last peak in sexual activity was the most important in both length and intensity. 3. The rhythm in sexual activity was entrained by the light-dark transition. 4. Female fertility was lowest during the period from 4 h before to 1 h after oviposition and greatest in the periods 8 to 4 h before and 1 to 7 h after oviposition. 5. The periods of maximum female fertility did not coincide with the periods of greatest sexual activity. More than 60% of all matings observed occurred during periods of intermediate female fertility. It would therefore appear that natural mating is not consistent with optimal female reproductive performance under artificial husbandry conditions. 6. The results are discussed in relation to a possible reduction in the number of males necessary in breeder populations in Muscovy ducks with a view to reducing the cost of producing ducklings.

Habitat selection, reproduction and survival of two small carabid species on arable land: a comparison between Trechus secalis and Bembidion lampros

In central Sweden, teneral adults of the strictly larval‐overwintering carabid beetle Trechus secalis Paykull started emerging during mid‐June and bred in midsummer (July). In contrast, the strictly adult‐overwintering carabid Bembidion lampros Herbst bred in early summer (June), and the new‐generation emerged in late summer (August). Both species appeared to be univoltine and had a short period of sexual activity (2–3 months). Their main oviposition periods did not overlap, and gravid B. lampros contained a higher mean number of eggs than did gravid T. secalis. Conversely, T. secalis had a longer oviposition period than B. lampros. Prereproductive B. lampros accumulated in high densities along field edges prior to hibernation. The cereal fields appeared to be optimal for reproduction and larval development of both species. Trechus secalis also reproduced in adjacent uncultivated habitats, whereas B. lampros did not. Trechus secalis larvae were completely subterranean, whereas B. lampros larvae were partly surface active. The adaptive significance of their reproductive tactics and habitat preferences as adults and the suitability of cereal fields as habitats for reproduction and survival of populations are discussed.

The transmission dynamics of the human immunodeficiency virus type 1 in the male homosexual community in the United Kingdom: the influence of changes in sexual behaviour

This paper examines the transmission dynamics of human immune deficiency virus type 1 (HIV-1) in the male homosexual population in the U.K. via numerical studies employing a mathematical model representing the principal epidemiological process. The model is based on an assumption of proportionate mixing between different sexual-activity classes (defined by the rate of sexual partner change per unit of time) and incorporates heterogeneity in sexual activity, distributed infection and incubation periods and the recruitment of susceptibles to the sexually active population. The sensitivity of model predictions to various assumptions and parameter assignments is examined. Numerical studies of model behaviour focus on the influence of changes in the magnitudes of the transmission parameters, associated with three periods of infectiousness during the incubation period of acquired immune deficiency syndrome (AIDS), on the magnitude and duration of the epidemic and on the level of the endemic equilibrium state. Predicted temporal trends in the incidence of AIDS are shown to be particularly sensitive to changes in the intensities and durations of the stages of infectiousness. Most of the paper addresses the influence of changes in sexual behaviour on the magnitude and duration of the epidemic. Numerical simulations show that the manner in which behavioural changes occur and who is influenced by such changes (i.e. infecteds or susceptibles, the sexually active population or new recruits to this population) have a major impact on the future timecourse of the epidemic. The greatest reduction in the incidence of AIDS over the coming decades is induced by changes in the rate of sexual-partner change among the sexually active population, particularly those currently infected. The time periods at which changes in behaviour occur, in relation to the starting point of the epidemic (assumed to be 1979), are also of particular significance to the future pattern of the incidence of disease and infection. Changes in behaviour early on in the timecourse of the epidemic have a much greater impact than equivalent changes at latter time points. On the basis of limited data on the pattern of change in sexual behaviour among the male homosexual community in the U.K., numerical studies of model behaviour tentatively suggest that the epidemic is at, or near to, a period of peak incidence of the disease AIDS. Analyses suggest that, following the peak in incidence, there will be a period of slow decline over many decades provided recent changes in behaviour are maintained in the coming years.(ABSTRACT TRUNCATED AT 400 WORDS)

Utilisation de l'habitat et organisation sociale du sanglier (Sus scrofa L.) à Doñana (Sud-Ouest de l'Espagne)

According to activity signs left on the ground (feces, footprints, and traces of rooting), wild boars on the Doñana Reserve preferentially occupy the marsh edge and the shrub area and, to a lesser extent, the marsh itself and the dryer zones of shifting or stabilized dunes. Habitat occupation follows a seasonal pattern, with the marsh edge being used progressively more from autumn to summer. The period of farrowing extends almost throughout the year, although virtually no births occur during the summer or in early autumn. Our data suggest two periods of sexual activity: an extended one during the summer, and a shorter one (although of greater influence on births) in late autumn. The basic social unit is the other group; several units may join to form larger family groups, which may comprise females with their young, rusty individuals, subadults, and sometimes male adults, although the latter tend to be solitary.

Teenagers' perceptions of unplanned adolescent pregnancies and oral contraceptive use.

Adolescent women who are sexually active often do not use contraceptives consistently and correctly. Adolescents are sexually active for an average of 15 months before initiating regular contraceptive use and the majority of young women who initiate use discontinue within the first year after initiation. This study enrolled 50 young women who initiated oral contraceptive use and was designed to provide more understanding of their perceptions about the possibility of an unplanned pregnancy and about contraceptive use. They were again contacted 6 weeks after initiation of oral contraceptives to assess continuation. Findings revealed that 90% of the subjects were sexually active at the time of the first visit; the mean period of sexual activity was 15 months. Only 30% had used a nonprescription birth control method during this period. While perceiving themselves to be highly susceptible to pregnancy, many young women continue to have psychosocial barriers to contraceptive use. Follow-up contact revealed more than 10% of the subjects were not using oral contraceptives.

Spawning of yellowtail snapper ( Ocyurus chrysurus Bloch 1791) in captivity

Observations on yellowtail snapper maturation indicated a long spawning season (March to October), including two periods of high sexual activity (March and July). Twenty-one batches of good quality eggs (mean viability rate 85%) were recorded without hormonal treatment. Spawning was also induced by HCG injection. Fecundity was high (172 000 eggs/kg), but the viability rate remained low (31%).

Beitrag zur klinischen Relevanz des Nukleinsäurenachweises der humanen Papillomviren (HPV) in Abstrichzellen der Cervix uteri

Cervical smears from 516 women were investigated cytologically and for the presence of papilloma virus (HPV) type 16/18 DNA sequences. From the cytologically normal smears (Pap I, II, IIw) 57/424 (13%) 16/18 were found HPV positive and from the pathological ones (Pap III, IIID, IVa, IVb, V), 30/92 (33%). The age prevalence of the HPV infection--provided a cytologically normal smear--appears compatible with the period of sexual activity, but persistence of the HPV infection has to be considered as a complicating factor. Our investigations on successive smears nevertheless permit the hypothesis that an HPV infection may disappear. The use of biotin-labeled nucleic acid probes yields results at least as reliable as those obtained with radioactive probes. The test for HPV positivity appears at present to be of limited diagnostic and prognostic benefit, particularly for the individual case. Investigations on fundamental oncogenic mechanisms are a different matter.

The reproductive cycle of male tomb bats, Taphozous hildegardeae (Chiroptera: Emballonuridae), in a seasonal environment of the African tropics

Two cave populations of Hildegarde's tomb bat had a reproductive cycle that corresponded closely to the rainfall‐induced seasonality of coastal Kenya (4s). Males had pronounced bimodal cycles of body weight due to the deposition of fat during periods of relative food abundance in both rainy seasons, and fat depletion during competitive mating and the dry seasons, when numbers of moths were lowest. The main period of sexual regeneration coincided with the increase in body weight experienced during the ‘long rains’ [April‐June) and led to mating. A secondary peak in the weights of male sexual glands, associated with the increase in body weight that occurred in the ‘short rains’ (October‐December), did not result in reproduction. It is suggested that this latter period of sexual activity was related to the maintenance of year‐round harems, and may represent the male response to a vestigial, bimodally polyoestrous, reproductive cycle.

Behavioral risk factors for HIV infection among homosexual men at a Boston community health center.

Social and behavioral factors associated with human immunodeficiency virus (HIV) infection were analyzed using cross-sectional data from homosexual and bisexual male clients of a Boston community health center. Partners from California, and a previous period of greater sexual activity (a "high period"), were independently associated with positive HIV antibody status, as were the frequency of receptive anogenital contact, both during the "high period" and during the last six months.

Effect of the Benguela temperature anomaly, 1982–1983, on the breeding cycle of Donax serra Röding

As part of an environmental monitoring programme for Koeberg nuclear power station near Cape Town, the breeding cycle and population dynamics of the white mussel Donax serra Roding were studied between early 1981 and the end of 1985. There is normally a cyclical pattern of high sexual activity during winter and spring and lesser activity during autumn. During summer, the proportion of sexually active animals is at its lowest and juveniles are at their maximum. During winter, juveniles are at their minimum. However, a major disruption of the pattern occurred at the end of 1982. The proportion of sexually active animals in the population increased dramatically during summer and settlement of larvae did not take place. In addition, there was no settlement of larvae from the abnormal summer breeding event. The normal cycle was resumed towards the end of 1983, with an extensive period of sexual activity followed by a major larval settlement. The period over which the abberations in the breeding cycle occurred,...

Courtship and Territoriality of Laboratory-reared Mexican Fruit Flies, Anastrepha ludens (Diptera: Tephritidae), in Cages Containing Host and Nonhost Trees

Courtship and territoriality of laboratory-reared Mexican fruit flies, Anastrepha ludens (Loew), were observed in cages containing host and nonhost trees. Both males and females preferred the undersides of host leaves at all times of the day. Females but not males also spent much time on fruit. Males established single-leaf territories on the undersides of host leaves beginning several hours before scotophase. Males exhibited sexual behavior, including elevation of the abdomen, puffing of pleural areas of the abdomen, eversion of a rectal pouch, and rapid wing vibration, on their territories. Most matings took place when females approached calling males, and males mounted following a brief and variable courtship. Most male–male agonistic behavior occurred on the undersides of host leaves during the sexual activity period. Female–female agonistic behavior occurred mostly on fruit before the sexual activity period and on the undersides of host leaves during the sexual activity period. Courtship and evolution are discussed in relation to other Anastrepha species.

CO2 laser vaporization for chronic cervicitis.

Chronic cervicitis is the most common disease occurring during the period of greatest sexual activity and reproductivity, and it is the most common gynecologic disease in young women. The disease is a common sequel to normal delivery and one of the main causes of infertility; it also may be precancerous. All the treated women in the present study exhibited preoperatively severe subjective symptoms for chronic cervicitis, and 32 out of 60 (53%) exhibited colposcopically atypical squamous epithelium. The women were examined 3, 6, and 12 months following laser surgery: 58 (97%) of them reported a decreasing intensity of their symptoms, and colposcopy revealed a normal postlaser transformation zone as well as a decreasing edema of cervical epithelium.

Testosterone and androstenedione profiles in the blood of domestic tom-cats

Testosterone and androstenedione were measured in the blood of four mature, intact tom-cats. Samples were collected from an indwelling jugular catheter once an hour for 24 h, and at more frequent intervals after a number of experimental procedures. Testosterone and androstenedione concentrations have a pattern of episodic release over a 24-h period but no diurnal rhythm was evident. The range of testosterone concentration was 0–23.5 ng/ml and androstenedione concentration 0–35.7 ng/ml. There was evidence of some seasonal influence on testosterone concentration, it being low in the period of reduced sexual activity (Jan–March) and high in the period of peak sexual activity (Aug). Sexual stimulation did not cause a rise in testosterone concentration as it was already high, but androstenedione concentration was significantly increased. Castration produced an immediate decrease in testosterone to baseline concentrations of 0–0.5 ng/ml but the concentration of androstenedione was variable and it is probable that a substantial amount of androstenedione is contributed from another source (possibly from the adrenals).

Variations annuelles du comportement d'oestrus, du taux et des possibilités d'ovulations chez la brebis Peulh du Niger

Annual variations in estrous and ovulation behavior were studied in 23 bicolored Peulh ewes for a period of 30 months. The percentages of estrus and ovulation shown over a year of observation were 76 and 86%, respectively. The average rate of ovulation was 1.3 +/- 0.04 (X +/- SEM). Reproductive activity was minimal from January to April, as the percentages of estrus and ovulation varied between 43.8 and 61% and between 53.1 and 86%, respectively. This period was marked by the advent of anestrus, interrupted frequently by silent and irregular ovulations. Anestrus lasted an average of 81.9 +/- 9.8 days (X +/- SEM). Reproductive activity was maximal from May to December, as the percentages of estrus and ovulation varied between 77 and 97% and between 87.5 and 100%, respectively. During this period ovarian activity was interrupted by prolonged diestrus which lasted an average of 24.9 +/- 3.3 days (X +/- SEM). The ovulation rate did not differ significantly (P greater than 0.05) between periods of minimal and maximal sexual activity. These results suggest that the reproductive potentialities of Peulh sheep on a good diet are comparable to those of certain ovine breeds in temperate zones. The results also suggest that anestrus in bicolored Peulh sheep is probably a different physiological process than the one observed in some breeds of sheep in which anestrus is marked by total ovarian inactivity.

Seasonal and stress related changes in plasma gonadotropins, sex steroids, and corticosterone in the bullfrog, Rana catesbeiana

Studies of seasonal gonadal cycles combined with direct measurements of plasma levels of the two gonadotropins (FSH and LH), several gonadal steroids (estrogen, E; progesterone, P; testosterone, T; and 5α-dihydrotestosterone, DHT), and the interrenal steroid corticosterone (B) were made in male and female bullfrogs in central California over a 5-year period (between 1976 and 1981). During the course of these studies, we discovered that levels of plasma gonadotropins and steroids are highly labile and particularly sensitive to the effects of captivity, especially in males. In animals captured and sampled repeatedly in the field over a 3-day period, hormone levels remained constant, but if held in collecting sacks, gonadotropin and gonadal steroids began to drop within 2–4 hr and usually reached “baseline” levels within 20 hr. This effect was apparent in all seasons, except occasionally in early spring when hormone levels dropped by only about half. Hormone levels were also generally depressed by the time commercially collected frogs reached local supply houses. Plasma B increased within 30 min of capture and remained high for days in captive animals. Blood samples taken from several hundred animals at the time of capture reveal pronounced seasonal cycles in all hormones measured. These changes are discussed in connection with other gross changes in gonadal condition and with regard to possible interactions among gonadotropins and steroids. Both sexes show a general elevation of hormone levels in spring and early summer, but the sexes differ somewhat both in timing and in magnitude of the changes, as well as in the nature of the dominant steroids. Pronounced “surges” in gonadotropins are evident around the time of gamate release in both sexes, but the temporal pattern of these surges is not the same for ovulation and spermiation; an elevation in plasma P is associated with the periovulatory surge in gonadotropins. Results were not entirely consistent with expectations of pituitary-gonadal relationships. Levels of plasma gonadotropins and steroids did not show the reciprocal relationship expected from a simple negative feedback between gonadal and pituitary secretion, nor did changes in gonadotropins and gonadal activities show the consistent positive correlation expected from a direct dependence of gonadal function on circulating gonadotropins. In females, plasma T, but not E, correlated with ovarian growth. Plasma T in females reached much higher levels than in males, but DHT was higher in males. Androgens were generally elevated during the period of sexual activity in males, but absolute levels did not correlate well with individual differences in sexual behavior. Thus, seasonal changes in testicular and ovarian activities cannot be accounted for solely by seasonal cycles in circulating gonadotropin levels.

Female mating relationships in rhesus monkeys.

Descriptions of the sexual behavior of social-living rhesus monkeys have indicated that mating patterns are characterized by the formation of consort pairs (mutually exclusive male-female associations) and also that females typically mate with multiple males. These reports raise the question of whether these are two different mating strategies or merely sequential phases in a unitary mating pattern. In order to examine this issue, the copulatory behavior of 27 adult females living in a heterosexual group housed in an outdoor compound was monitored both by group scan and focal sampling technique. Females displayed discrete periods of mating, characterized by one or more copulations per 4 hr observation period. During their sexually active periods, females copulated with multiple males (X̄ = 5.22, SE = 0.37). Among the 103 cases where females had multiple copulatory series on the same day, the successive series involved new males significantly more often than the previous partner. When a female did copulate repeatedly with a male on a given day, both she and her partner were significantly more often of high social rank. Furthermore, the interval between successive copulations was significantly longer when the second copulation was with her previous partner as compared to a different male. Analysis of female behavior for a one-hour period following a copulation indicated that females continued to be sexually active and that those new sexual interactions more often involved a new male. Thus, females not only copulated with multiple males throughout their inclusive period of sexual activity, but also interacted with multiple males on any give day they were sexually active. Since repeated copulations with the same male were rare and occurred when both members of the pair were high ranking, the consort relationship probably does not describe a characteristic mating strategy. The more pervasive pattern is for a female to sexually interact and have copulations with multiple males.

The effects of the male sex-hormone testosterone on body temperature and energy metabolism in male japanese quail ( Coturnix coturnix japonica)

1. 1. Castrated male quails (C) show a higher mean body temperature ( T b ) during the day than intact males (M): 42.2/41.8°C. At night, T b of C is lower than T b of M: 41.1/41.3°C. 2. 2. Substitution of testosterone in C causes an abolishment of the observed differences. 3. 3. During the day under natural light-dark conditions, T b shows circannual variations in M, with lower levels during the period of sexual activity. 4. 4. The level of energy metabolism is lower in castrates than in M, both during the day and night. The resting metabolism was not influenced by testosterone substitution. 5. 5. Thermal conductance is 11% lower in C than in M (1.32 J/K·g·hr; 1.44 J/K·g·hr) due to better insulation of C (e.g. higher fat deposits). 6. 6. The possible importance of the observed effects in free-living birds is discussed according to their energy requirements.