The camelids (camels, llamas and alpacas) diverged from the lineage leading to the true ruminant species at least
40 MYA. The female camel is a seasonal breeder and only ovulates in response to mating. The CL develops within a few days, functionally plateaus around day 8 9 postcoitum, and then promptly regresses. Thus the conceptus must initiate its signal within about a week of conception if the pregnancy is to be maintained. In nonpregnant dromedary camels, basal concentrations of PGF2a rise and progesterone levels fall after day 8 of the cycle, thereby implicating PGF2a as the luteolytic factor, although oxytocin appears not to be involved. The nature of the antiluteolytic signal remains unknown, but it is almost certainly not IFN-t.
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