Quantitative microscopic structure of testis in adult Arabian rams, raised under closed grazing system in Khuzestan province of Iran, was studied in four seasons over a one year period. For this purpose, thirty adult rams were randomly selected and the live weight and scrotal circumference of rams were recorded. At the beginning of each season, among the study group, four rams were randomly sel...

The following article is a summary of research on the influence of season on the reproductive processes in undomesticated animals. The results presented below show: a/ an annual hormonal profile of domestic pig and wild boar crossbreed and the antioxidant blood system in the different seasons, b/ the possibility of gonadptropic hormone stimulation in chinchillas which are in diestrus or inferti...

Cyclical parthenogens, which combine asexual and sexual reproduction, are good models for research into the ecological and population processes affecting the evolutionary maintenance of sex. Sex in cyclically parthenogenetic rotifers is necessary for diapausing egg production, which is essential to survive adverse conditions between planktonic growing seasons. However, within a planktonic seaso...

Although the amount of energy that males and females invest in reproduction is an integral component of theories explaining the evolution of particular mating strategies, few studies have actually determined the amount of energy that each sex allocates to reproduction. We compared how energy is expended by male and female Anolis carolinensis lizards during both the breeding and postbreeding sea...

Toward the end of the breeding season, migratory songbirds face crucial tradeoffs between the timing of reproduction, molt, and migration. Using stable hydrogen isotopes, we show that male American redstarts investing in high levels of reproduction late in the season adopt a unique strategy of combining molt and migration. Tail feathers molted during migration also reflect less orange-red light...

The seasonally determined demographic structure of two semi-arid rodents, both agricultural pest species (the leaf-eared mouse (Phyllotis darwini) in Chile and the multimammate mouse (Mastomys natalensis) in Tanzania), is analysed using capture-mark-recapture (CMR) statistical models and measures for elasticity (the relative change in the growth rate due to a relative unit change in the paramet...

background: brownbanded bamboo sharks (chiloscyllium punctatum) is one of the cartilaginous fish that lives in the persian gulf. objectves: the purpose of the present study is to study the effects of thyroid hormone on reproductive system of this specious. methods: in this investigation, 36 individual of brownbanded bamboo sharks (chiloscyllium punctatum) in both autumn (before reproduction) an...