The mechanisms that control growth and reproduction have received considerable attention by molecular and cellular endocrinologists, yet there has been relatively little effort to link these two aspects of physiology. On the other hand, evolutionary biologists have long commented on the relationship between growth and reproduction in many species, yet have generally neglected the mechanisms und...

A multigroup SIR epidemiological model is used to study the effects of group-targeted vaccination strategies on disease control and prevention. The model takes into consideration both proportionate and preferential mixing patterns between groups. We show that the dynamical behaviors of the model are determined by the control reproduction number R(v) and, under certain conditions, by the type-re...

The seasonality of reproductive activity in the ewe in temperate latitudes is controlled by photoperiod. Its annual variations control the temporal organization of the sexual cycle by changing the activity of the gonadotrophic axis. Cyclic oestrous behaviour usually appears in the ewe at the end of summer or the beginning of autumn and finishes in winter or at the very beginning of spring. Seas...

the pollution of aquatic ecosystems may affect natural reproduction of fish populations by decreasing the fertilization efficiency. among the various sources of pollution, heavy metals are important group, being found in both freshwater and marine environment. the present study investigated changes of sperm characteristics of caspimyzon wagneri when exposed to manganese (mn). spermatozoids were...