Annual Variation in the Plasma Testosterone in Microcebus murinus

Petter‐Rousseaux, A.; Picon, R.

doi:10.1159/000155994

Cited by 23 publications

(12 citation statements)

References 23 publications

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“…An obvious activity continues till the end of July. Testosterone dosages in plasma corroborate this annual cycle of Leydig cells [Petter-Rousseaux and Picon, 1981], As it is the case in most seasonal animals, Leydig cells reach their maximal activity well before sper matogenesis is complete. In males which died after exhaustion, a significant decrease in nuclear diameter of the Leydig cells is noticed during the period of activity (p < 0.05).…”

Section: Interstitial Cellssupporting

confidence: 74%

Stress-effects in Microcebus murinus

Perret¹

1982

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Histological investigations were made over a 10-year period on 164 lesser mouse lemurs that died spontaneously in captivity. The principal lesions found were chronic nephrosis with nephritis which affects 90% of the animals, myocardial necrosis, respiratory insufficiency induced by interstitial pneumonia, fatty changes in the liver, and splenic and gastric lesions. The following are associated with these pathologies: progressive hypothyroidism, stable hypercorticism, slight medulloadrenal hyperactivity, and sexual disorders such as testicular atrophy in males and estrous cycle disturbance or uterine tumor in females. All these data were treated by correspondence analysis; this showed that, except for some rare cases of death which can be attributed to massive parasitic infestation or generalized cancer, the whole captive population of lesser mouse lemurs is suffering from a syndrome that leads to renal insufficiency and death. Most of the observed pathologies are considered as being associated with aging in mammals. But captive Microcebus murinus died between 3 and 4 years of age, whereas their potential life survival is 13 years. Our hypothesis is that these pathologies arise due to an overload of cortico- and medulloadrenal secretions. The above-mentioned hormonal imbalance could be induced by stress factors occurring in captivity, the most important of which would be social stress.

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Section: Interstitial Cellssupporting

confidence: 74%

Stress-effects in Microcebus murinus

Perret¹

1982

IJFP

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“…M. murinus is typically a photoperiod-dependent species, and several circannual rhythms have been demonstrated. In addition to seasonal variations in reproductive function in both sexes [14][15][16], body weight, body temperature, locomotor and feeding ac tivities. thyroid, adrenocortical and adrenomedullary functions undergo cyclic changes that are regulated by variations in day length [14,[17][18][19][20][21].…”

Section: Methodsmentioning

confidence: 99%

“…Seasonality Seasonal and circadian variations in plasma testosterone concentrations in the male lesser mouse lemur, under natural pho toperiod conditions in Paris, are now well known [15,16,24], During the non-breed ing season (autumn), the testes are complete ly involuted without gametogenic activity, plasma testosterone levels are low (= 5 ng/ml) and no apparent diurnal changes arc present. In early winter, the testes enlarge to 5-10 times their quiescent volume, complete sper matogenesis is found and plasma testosterone concentrations reach 50-70 ng/ml (among the highest values recorded for mammals).…”

Section: Photoperiodic Regulation Of Sexual Functionmentioning

confidence: 99%

Environmental and Social Determinants of Sexual Function in the Male Lesser Mouse Lemur (Microcebus murinus)

Perret¹

1992

IJFP

181

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Environmental factors that regulate the sexual activity of male lesser mouse lemurs have been studied experimentally with more than 60 captive animals over an 8-year period. In this nocturnal Malagasy prosimian, variation in day length is the primary factor controlling seasonal sexual activity. Plasma testosterone concentrations were low (= 9 ng/ml) during short days and reached 60 ng/ml during long days (>12-hour day). This cyclic pattern persists unchanged when artificial photoperiodic rhythms are applied and is not altered by ageing. The timing of puberty is also regulated by photoperiodic changes. Nevertheless, the sexual activity of the male lesser mouse lemur can be dramatically modified by the social environment. In heterosexual groups, behavioural and physiological components of sexual activity are depressed in all males except the dominant one, whose aggressive interactions are always successful. Intermale sexual inhibition was shown to be mediated by chemical cues present in the urine of dominant or isolated males but not in urine of subordinate individuals. The inhibitory signals possess lipophilic properties and are not contingent on the gonadal activity of the urine donor but are linked to adrenocortical activity. By contrast, chemical signals stimulating the reproductive function of all males are found in the urine of females, the presence of which is required for the establishment of clear dominance among grouped males. Endocrine mechanisms underlying intermale sexual inhibition by chemical cues were analysed. Variations in prolactin strongly suggest that olfaction interacts with the photoperiodic regulation of reproductive function, leading to changes in the sensitivity of the negative feedback effect of testosterone on gonadotrophin secretion. Inhibitory or stimulatory effects of chemical signals are discussed in the context of their functional significance for wild populations.

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“…Sexual inhibition is mediated by chemical cues present in the urine of the dominant male [7,9]. Reproductive activity and body mass are influenced by social rank and variation in day length [6][7][8][10][11][12][13][14][15][16]. In the wild, reproduction starts with the beginning of the rainy season, just after a period of decreased food supply during the dry season [15].…”

Section: Introductionmentioning

confidence: 99%

Body Mass in Wild Microcebus murinus over the Dry Season

Fietz¹

1998

IJFP

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The main aim of this field study was to compare adult male and female grey mouse lemurs (Microcebus murinus) with respect to body size, seasonal changes in body mass, onset of reproductive activity and sex ratio of captured animals. M. murinus was studied in the dry deciduous forest of western Madagascar. The lemurs were trapped in capture/recapture sessions during the dry season of 1993 (August, September, October). In order to verify results of studies in captivity concerning body mass and rank order among males, distribution patterns and body mass of males and females were examined. The results of this study indicate that rank in males is related to body mass and testes size, rather than determined by body size. Heavier males occurred closer to females, possibly facilitating access to breeding opportunities. There was no sexual dimorphism in body size. Differences between the sexes in seasonal changes in body mass, and in numbers of each sex caught, indicate that males and females have different activity patterns during the dry period, when food availability is restricted.

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Annual Variation in the Plasma Testosterone in Microcebus murinus

Cited by 23 publications

References 23 publications

Stress-effects in Microcebus murinus

Stress-effects in Microcebus murinus

Environmental and Social Determinants of Sexual Function in the Male Lesser Mouse Lemur (Microcebus murinus)

Body Mass in Wild Microcebus murinus over the Dry Season

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