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In this paper, we suggest an alternative mechanism based on the failure of polar body emission, followed by fertilization of multiple haploid nuclei through polyspermy and subsequent competition of Z and W bearing cells within chimeric embryos.
Although the occurrence of failure of polar body extrusion is obvious from the observations of chimeric birds, the idea that it could be the first step of offspring sex ratio bias has been entirely overlooked.
Specifically, it is believed to be determined at the first meiotic division (MI), during which the sex chromosomes segregate (Rutkowska and Badyaev 2008). Importantly, the observed SR biases could be likewise explained by an alternative mechanism, which is also molded by hormones and acts during MI.
Recent evidence suggests that offspring SR bias via segregation distortion might be induced by acute hormonal treatment (Gam et al. The main idea of our hypothesis (Figure 1) is that hormonal fluctuations caused by external factors encountered by the female alter the normal process of MI by blocking segregation of the first polar body (PB)—a phenomenon responsible for the occurrence of mixed-sex chimeras in birds (Hollander 1975; Zhao et al. As a result, the first PB with its full set of chromosomes remains in the active cytoplasm of the ovum.
In 2015, we implemented a sanatorium snack feeding program for eight weeks during the summer.Environmental and social effects on offspring sex ratio bias in birds are among the most studied topics in evolutionary biology.Although it is established that offspring sex is determined at the stage of the first meiotic division, there is no direct evidence for the common belief that the bias happens via nonrandom sex chromosome segregation.Donations of unused diapers, incontinence pads, mattress sheets (cribs and twin beds) are valued and welcomed for ages four to adult. Our long term goal is to provide non-emergency dental care for all the orphans.