Aging and Loss of Fertility in Male and FemaleBrachionus plicatilis(Rotifera)

Summary The decline with age of mictic female susceptibility to fertilization and male capacity for fertilization is characterized for the rotifer Brachionus plicatilis. All mictic females were susceptible to fertilization until age 4 hr. Susceptibility then declined non-linearly according to the quadratic equation Y = 140.6—14.3X + 0.36X 2. By age 24 hr, sexual females no longer could be fertilized. Only 83% of newborn males were capable of fertilization. This level of fertility held until age 8 hr, then declined linearly. The age when 50% of individuals were no longer fertile was termed the length of fertilizability 50(LF50) and is 7.9 hr (16.7% of lifespan) and 18.8 hr (26.1% of lifespan) for females and males, respectively. Newborn males had an average of 30.1 ± 1.40 motile sperm. Males transferred a mean of 2.3 motile sperm into the pseudocoelom of females on each insemination. Sperm inseminated per copulation closely corresponds to the mean number of resting cysts produced by fertilized females. It is not likely that resting cyst production is limited by sperm availability.