Robert Mauget

Seasonal and Fasting-Related Changes in Circulating Gonadal Steroids and Prolactin in King Penguins, Aptenodytes patagonicus

Temporal correlations between reproductive endocrinology and the breeding and molt cycle of the king penguin were studied at the Crozet Islands, in the southern Indian Ocean. This species is unique in having a long cycle (14-15 mo), mainly due to a prolonged fledging period (11 mo), which includes the austral winter. Plasma gonadal steroids and prolactin were at their minimum levels during the prebreeding molt. However, circulating testosterone (males) and estradiol and progesterone (females) were already elevated at the time of arrival at the colony to breed, and the levels peaked during copulation. After laying plasma steroids decreased but remained above basal levels during the following months. Prolactin was low during the sexual phase of the reproductive cycle of both males and females. It reached high plasma concentrations in incubating birds and remained elevated during the whole fledging period. Possible roles for sustained high prolactin levels in winter and spring, which involve the care of the single chick and the prevention of a new cycle, are discussed. The effect of nutritional status of birds on plasma reproductive hormones was also investigated in relation to brief (brooding shifts) and prolonged (incubation spells)fasting. No major effect of food deprivation on plasma hormones was found in incubating and brooding king penguins during normal shifts. However, birds with a low body mass (<9 kg), which progressively mobilized their body protein, presented higher progesterone levels and lower plasma testosterone and prolactin. The decrease in plasma prolactin may be involved in the spontaneous abandon of reproduction previously described in penguins that have depleted their fat stores.

Endocrine Correlates of Parental Care in an Antarctic Winter Breeding Seabird, the Emperor Penguin,Aptenodytes forsteri ☆

Plasma levels of luteinizing hormone (LH) and prolactin associated with parental behavior were measured in the Antarctic winter breeding emperor penguin, Aptenodytes forsteri. Males exclusively incubate the egg while females exclusively brood the nonhomeothermic young; both sexes alternate in rearing the homeothermic young. Birds were sampled on arrival from the sea through egg laying, incubation, and brooding. All parent birds lost their chicks at the end of the brooding period due to harsh weather but sampling continued. In females, LH titers dropped after egg laying but levels were restored when the birds returned from the sea to brood the chicks and were not depressed by high prolactin levels. Plasma prolactin remained low in males captured on arrival and kept until the free-living males finished incubation. In breeders, prolactin secretion increased during the prelaying period when day length decreased. Prolactin levels stayed elevated in males during incubation and in brooding females returning after a 2-month absence at sea. Prolactin values were higher in brooding females than in males ending incubation or returning in late brooding. These levels did not drop after chick loss, and the sexual difference in prolactin values was maintained after breeding failure. In emperor penguins, increased prolactin secretion appears to be triggered around the time of egg laying and continues, driven by an endogenous mechanism, through incubation and brooding until rearing is completed. Prolactin secretion independent of external stimuli may have evolved in pelagic seabirds to maintain parental care despite long absences at sea from the breeding colony.

Effects of fadrozole on sexual displays and reproductive activity in the female canary

We used fadrozole, a potent inhibitor of the aromatization of androgens to estrogens, to investigate the influence of estradiol on copulation solicitation displays (CSD) and reproductive activity in female canaries (Serinus canaria). Systemic injections of fadrozole during 10 consecutive days were effective in reducing plasma estradiol concentrations in adult female canaries submitted to photostimulation. Fadrozole provides a powerful tool for limiting an individuals exposure to estradiol, and the results of this study emphasize the influence of estradiol secretion in the regulation of behavioral transitions along the reproductive cycle of the female canary. When females were injected at the beginning of photostimulation, the emergence of copulation solicitation displays in response to conspecific songs was delayed. When females were injected later, after they were sexually active, the fadrozole treatment did not affect sexual displays. These results are consistent with the hypothesis that a threshold level of estradiol is critical to activate the neural circuitry mediating the copulation solicitation displays response in the female canary. They also suggest that the magnitude of sexual response is not related in a dose-dependent manner to estrogen concentrations observed during the period of sexual responsiveness. When females were injected at the beginning of photostimulation, egg-laying was delayed; when females were injected later, after they were sexually active, the fadrozole treatment dramatically reduced egg-laying and prevented incubation.

Behaviours of collared and white-lipped peccaries (Tayassu tajacu andT. pecari) in relation to sexual receptivity of the female

Changes in behaviours of the two peccary species,Tayassu tajacu Linnaeus, 1758 andT. pecari Link, 1795 between non-receptive and receptive periods were followed by presenting females to males daily for 15 minutes. InT. tajacu, the rank order of behaviours, similar in both sexes during the non-receptive period, differs during receptivity. Contact behaviours decrease in males, whereas sexual ones progress. The same tendency appears in females. Inhibited bites replace markings of partner as the most common behaviour in both sexes. InT. pecari, the rank order of behaviours always differs between sexes. When females become receptive, the differences from the non-receptive period are neither numerous nor significant. The most common behaviour of males, previously markings of partner, becomes mounts, whereas in females agonistic behaviours reinforce their dominance. In this species, the only behaviours that increase are those leading directly to copulation or those of an agonistic nature. In both species, females show more agonistic behaviours than males (mainly inhibited bites inT. tajacu, truly aggressive ones inT. pecari). When females are receptive, males ofT. pecari become less active, contrary toT. tajacu where both sexes double their activity. InT. tajacu, most behaviours vary significantly in relation to the progesterone level, contrary to the other species. These pecularities appear correlated to herd composition and organisation.

Effects of melatonin implantation or artificial long days on seasonal ovulatory activity in roe deer (Capreolus capreolus L.)

Abstract Three experiments were conducted to determine the effects of melatonin implantation or photoperiodic changes after the winter and summer solstices on the onset and cessation of the annual ovulatory season in the female roe deer. In the first experiment five adult female roe deer received melatonin implants from 16 April. Three females were kept as controls and received no melatonin treatment. Treatment induced a rapid and sharp decrease in prolactin concentrations and advanced the ovulatory period by 72 days (first progesterone increase: 4 June versus 10 August in melatonin-treated versus control females, respectively; P = 0.022). In the second experiment four adult female roe deer received melatonin implants on 13 January. Because of the natural presence of a persistent corpus luteum in the female roe deer, females received monthly injections of prostaglandin analogue in order to determine if they were able to re-ovulate after induced luteolysis. Last date of elevated progesterone concentration was observed later in melatonin-treated females than in non-melatonin-treated females of the preceding year. In the third experiment, four adult females were kept in light-proof rooms and exposed to long days (16L(light):8D(dark)) from the summer solstice. Exposure to long days delayed by 46 days the first ovulation (first progesterone increase: 14 October vs. 28 August in long-day-treated vs. control females, respectively; P = 0.014). Treatment of female roe deer with melatonin implants in April can induce a substantial advance of ovulatory activity; prolonged exposure to melatonin after 13 January extends the sexual season and ovulation was delayed in females exposed to long days after the summer solstice. These results suggest that the female roe deer initiates its breeding season in August after perceiving shortening days and ends it in February after perceiving lengthening days.

Metabolic cost of first reproduction in young female European roe deer Capreolus capreolus

In female roe deerCapreolus capreolus (Linnaeus, 1758), like in several deer species, first reproduction occurs before they have reached their full body size. This study quantifies, in young females, the energetic costs induced by the contemporaneously occurring events: growth and first reproduction. Resting metabolic rate and body mass were measured in young primiparous females from first mating to 4 months after parturition, and compared to values measured in fully-grown adult multiparous females. Throughout the 10-month period from mating to fawning, body mass increased in yearlings. Prior to the blastocyst implantation (month −5 before parturition) young females were lighter than adult females whereas after parturition they had the same body mass. Our results suggest that body growth was reinitiated during pregnancy in primiparous females. From mating to fawning, except in the first part of pregnancy, mass-specific metabolism was higher in primiparous females than in multiparous individuals indicating the occurrence of an additional cost due to growth in young females. The depressed level observed at the beginning of gestation could allow the resumption of growth at lower cost. Thus, the allocation of resources to both reproduction and growth was not detrimental to first reproduction in young female roe deer under experimental conditions withad lib feeding.

Seasonal Regulation of the Sexual Cycle and Antler Growth in Roe Deer: Evidence for an Endogenous Rhythm

Seasonal variations of luteinizing hormone (LH), prolactin (PRL), and testosterone were analyzed in relation to the annual cycle of antlers in four adult roe deer (Capreolus capreolus) living under the natural photoperiod and adult males exposed to manipulated photoperiods. In the second experiment, one male was exposed for 15 months to an artificial photoperiod providing two complete cycles per year. In the third experiment, two males were exposed for 9 months to an artificial photoperiod providing 8 h of light and 16 h of dark (8L:16D), while two control males were kept in a light-proof room subject to the natural photoperiod. At monthly intervals blood samples were taken every 15 min 2h after an injection of gonadotrophin-releasing hormone (GnRH). High LH activities were correlated with increasing day length, (in January, 2.69 ± 0.25 ng/ml, and in May, 3.27 ± 0.56 ng/ml), while high LH levels were again recorded in the fall when day length was decreasing (in October, 1.89 ± 0.66 ng/ml) in the animals living outside in natural photoperiod. In deer kept under manipulated photoperiods, sexual cycles and antler cycles were modified. For the second experiment, a biphasic pattern of LH was observed during the first 6-month photoperiod, whereas during each following photoperiod cycle a single peak was observed. The bucks exposed to the 8L:16D photoperiod exhibited two periods of high LH levels (January–February and August). Moreover, two antler cycles recorded during the 9-month experiment. These results provide evidence for an endogenous rhythm of LH occurring after the winter solstice. The pituitary activity could be later entrained by the long photoperiod (> 12L) after the spring equinox.