Color images of figures 4-9 from the report, The Reproductive Biology of Yellowfin Tuna (Thunnus albacares) in Hawaiian Waters and the Western Tropical Pacific Ocean: Project Summary, by David G. Itano
SOEST 00-01, JIMAR Contribution 00-328
School of Ocean and Earth Science and Technology
University of Hawaii, Honolulu, HI, January 2000

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Figure 4. Transverse section of immature ovaries of yellowfin tuna indicating
oocytes in advancing developmental stages.

Thumbnail of Fig. 4a (a) Stage 1: Immature with early stage, unyolked oocytes @40x. Thumbnail of Fig. 4b (b) Stage 2: Immature, unyolked but developing oocytes @40x.
Thumbnail of Fig. 4c (c) Stage 3: Immature, mix of unyolked (uy) and partially yolked (py) oocytes @40x.  

Figure 5. Transverse section of mature yellowfin ovaries in different stages.

Thumbnail of Fig. 5a (a) Stage 4: Mature reproductively inactive tuna with unyolked (uy), partially yolked (py), & alpha atresia of fully yolked oocytes @100x. Thumbnail of Fig. 5b (b) Stage 5: Mature, potentially reproductive with fully yolked (fy) oocytes present @40x.
Thumbnail of Fig. 5c (c) Stage 6: Reproductively active, fully yolked, oocytes and post ovulatory follicles (po) present @100x. Thumbnail of Fig. 5d (d) Stage 7: Reproductively active, fully yolked oocytes & post ovulatory follicles (po) present with significant atresia of fully yolked oocytes @100x.

Figure 6. Fully yolked yellowfin oocytes in stages advancing toward ovulation.

Thumbnail of Fig. 6a (a) Normal, fully yolked oocyte with well developed yolk globules @100x. Thumbnail of Fig. 6b (b) Coalescent stage oocytes with lipid droplets combined into larger oil droplets (od) surrounding the nucleus (n). Degenerated post ovulatory follicles (po) are evident @100x.
Thumbnail of Fig. 6c (c) Migratory nucleus stage oocyte with lipid combined into one large oil droplet with the nucleus (n) migrating toward the animal pole @100x. Thumbnail of Fig. 6d (d) Early hydrated (eh) oocytes showing disintegration of the nucleus and fusion of yolk globules into larger yolk platelets @40x.
Thumbnail of Fig. 6e (e) Fully hydrated (fh) oocytes with a degenerated post ovulatory follicle (po) evident, indicating daily spawning periodicity @40x.  

Figure 7. Ovary samples from the Hawaii region (Area F) progressing from
a fully yolked to fully atretic, postspawning condition.

Thumbnail of Fig. 7a (a) Stage 8: Some fully yolked oocytes (fy) with significant a (a at) and b (b at) atresia of fully yolked oocytes @100x. Thumbnail of Fig. 7b (b) Stage 9: 100 percent a atresia of fully yolked oocytes @40x.
Thumbnail of Fig. 7c (c) Stage 9: 100 percent a and b atresia of fully yolked oocytes @40x. Thumbnail of Fig. 7d (d) Stage 9: Advanced a (a at) and b (b at) atresia @40x.

Figure 8. Ovary samples progressing from a fully atretic
to reproductively active condition.

Thumbnail of Fig. 8a (a) Stage 10 sample @40x. Thumbnail of Fig. 8b (b) Stage 10 sample with unyolked but developing oocytes @40x.

Figure 9. Postovulatory follicles of differing ages and stages of degeneration.

Thumbnail of Fig. 9a (a) Age zero post ovulatory follicles (po) @100x. Thumbnail of Fig. 9b (b) Good condition post ovulatory follicles less than 6 hours old @100x.
Thumbnail of Fig. 9c (c) Post ovulatory follicles less than 12 hours old @100x. Thumbnail of Fig. 9d (d) Post ovulatory follicles in advancing stages of degeneration with coalescent stage oocytes @100x.
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This page updated March 15, 2000