Sun et al.: Reproductive biology of Makaira nigricans 
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Figure 2 
Micro-images of whole oocytes and sectioned oocytes of blue marlin ( Makaira nigricans) from dissecting and light 
microscopes, respectively. (A) CN, chromatin nucleolar oocytes; PN, perinucleolar oocytes; PV, previtellogenic oocytes; 
(B) VT, vitellogenic oocytes; HY, hydrated oocytes; (C) POF, postovulatory follicles; AO, atretic oocyte. Scale bars: 
100 microns. 
Oogenesis and ovarian development 
The most advanced group of oocytes for each ovary 
were classified as 1) unyolked — oocytes that had not 
begun vitellogenesis (chromatin nucleolar oocytes and 
perinucleolar oocytes, Fig. 2A); 2) early yolked — oocytes 
in the early vitellogenic stage (previtellogenic oocytes, 
Fig. 2A); 3) advanced yolked — oocytes in an advanced 
vitellogenic stage (vitellogenic oocytes, Fig. 2B); and 4) 
hydrated — unovulated hyd rated oocyte stage (hydrated 
oocytes, Fig. 2B). Furthermore, the presence or absence 
of postovulatory follicles and atresia of yolked oocytes 
were identified and recorded for the determination of 
ovarian maturation (Fig. 2C). 
The ovaries of 394 females could be staged into six 
ovarian development stages based on microscopic char- 
acteristics and the most advanced group of oocytes 
(Fig. 2 and Table 1). Ovaries were classified as im- 
mature (OM1) if they were packed with unyolked oo- 
cytes, maturing (OM2) when the unyolked oocytes 
were growing to early yolked oocytes, and mature 
(OM3) if they contained advanced yolked oocytes, but 
did not exhibit atresia. Ovaries that contained a mi- 
gratory nucleus and hydrated oocytes, but for which 
no POFs were found, or for which there were unovu- 
lated hydrated oocytes and POFs, were classified as 
spawning-spawned (OM4). Ovaries with early yolked, 
advanced yolked, and atretic oocytes were assigned to 
the recovery stage (OM5). For resting ovaries (OM6), 
the unyolked oocytes were not packed as orderly as 
those in immature ovaries, and a few atretic oocytes 
were observed occasionally. 
