Combined assessment of data obtained in in vitro assays and in vivo fish tests reveals information on the underlying mechanism of action of the tested substance in fish, for example, reduced fertilization rate due to inhibition of androgen receptor activity in males.
In haplodiploid species a reduced fertilization rate leads to the production of more sons.
Selection for the reduced fertilization rate leads to a spread of these alleles through both the infected and uninfected population, eventually resulting in the population becoming fixed for both the PI- Wolbachia infection and the reduced fertilization rate.
Matalliotakis et al. recently found a significantly reduced fertilization rate in women with BMIs of at least 24 kg/m, when compared with those with BMIs of less than 24 kg/m (58.9 vs. 51.7%%) [ 10].
For mature male parr, both decreased body and gonad growth may give an additional disadvantage through reduced fertilization rates during breeding.
Despite the bulk of previous studies, some researchers have found reduced fertilization rates in obese women [ 2– 5], but others have not [ 18– 20].
We found that not only did the KO males produce similarly reduced fertilization rates (Fig. 2 B) but also there was a difference in the status of cumulus oophorus.
Decreased pH had a significant effect in reducing fertilization success, with temperature significantly increasing fertilization.
In our study, despite similar ratios of mature oocyte counts obtained in all weight groups, decreased fertilization and clinical pregnancy rates are suggested as factors related to decreased oocyte quality related to reduced fertility rates.
The ultimate result of this process is the fixation of mutant alleles reducing the fertilization rate both in the infected and in the uninfected segments of a population.
In agreement with previous findings that obesity is associated with an impaired response to fertility treatments and negatively affects pregnancy outcome [ 16, 17], we found that overweight patients had less fertilized and 2PN embryos as well as reduced fertilization and 2PN rates, which may be attributed to the metabolic disturbances of obesity-related AAs such as BCAA and glutamic acid.
