In most cases, the atresic cytoplasm stained more intensely, becoming darker compared with that of healthy oocytes.
Characteristics of atresia were observed in early and late vitellogenic oocytes (atresic immature oocytes), and in mature oocytes (atresic mature oocytes), beginning in April and throughout gametogenesis and postspawning resorption (Fig.
(1) Atresic volume fraction (AVF): the number of grid points occupied by AO divided by the total number of grid points occupied by all oocyte types.
(4) Minimum atresic impact (MAI): the minimum impact of atresia on the oocyte population, expressed as
The MAI was based on three assumptions: (1) MVF (composed of healthy, mature oocytes) represented the oocyte volume fraction with a high probability of being spawned as healthy; (2) AVF represented the oocyte volume fraction with no probability of being spawned as healthy oocytes; the fates of MVF and AVF were therefore known; (3) The fate of IVF was unknown as it could either remain healthy or become atresic. This index, therefore, represents the minimum oocyte volume fraction known to be atresic, compared with the total oocyte volume fraction whose fate is known.
3): active development, mostly vitellogenic oocytes (516-2,743 [micro][m.sup.2]); ripeness, comprising postvitellogenic oocytes (1,073 2,930 [micro][m.sup.2]); partial spawning with residual oocytes (145 2,939 [micro][m.sup.2]); and spent stage, mostly
atresic oocytes (331 2,001 [micro][m.sup.2]).