Age at sexual maturity among male polar bears ( Ursus maritimus ) and timing of the mating season were studied by microscopic and macroscopic analysis of the reproductive organs from 165 male and 92 female Greenland polar bears. Males became sexually mature in the spring following their fifth bir...
J Markofsky,A Perlmutter 摘要: Aging was studied in the male, annual Cyprinodont fish, from East Africa, Nothobranchius guentheri. Median life-span of the population was 14 months at 21–25°. It was observed that there was variability in the onset of sexual maturity. When the population ...
Transfer from 8 to 16-h photoperiods at 5 weeks of age had no effect on AFE. At 7 weeks there was a bimodal response with some pullets subsequently showing advanced maturity and others not. Maximum stimulation of early maturity (31 days on average for the two genotypes) was obtained at ...
Age determination, validation, growth and minimum size of sexual maturity of the Greenland smooth cockle (Serripes groenlandicus, Bruguiere, 1789) in Easte... The Greenland smoothcockle () has a circumpolar distribution in the northern hemisphere. Despite such a wide range and potential commerci...
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Experiments with prepubertal hamsters were undertaken to determine if the appearance of spermatozoa with fertilizing capacity in the cauda epididymidis is related to age and/or body weight and whether the development of sperm function coincides with complete maturation of the mating behaviour pattern. ...
We present the first study of bone microstructure in Suuwassea emilieae, a diplodocoid sauropod from the Morrison Formation. Although the holotype of Suuwassea was recently identified as a subadult, bone histology demonstrates that this individual had reached sexual maturity at approximately 75–80...
Irrespective of genotype, plasma FSH for pullets given a decrease in illuminance at 63 or 112d showed a tendency for less change than did constant-illuminance controls. 3. There was no significant difference in sexual maturity for ISA Brown maintained on 3 or 25lux, but Shaver White pullets ...
The influences of age (4 to 12 wk), sexual maturity status, and sex on hypothalamic-pituitary-adrenal (HPA) axis responsiveness were investigated by measuring changes in peripheral basal levels of corticosterone (B) and responses to 10 min of physical restraint in a crush cage or injection of...
—After performing the miracles that take us from conception to birth, and then to sexual maturation and adulthood, natural selection was unable to favor the development of a more elementary mechanism that would simply maintain those earlier miracles forever. The manifestations of this failure are ca...