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Table 2.
Description of the maturity stages of B. amphigramma gonads based on modified gonad maturity schemes from Ntiba and Jaccarini (1990).
TestesOvaryOvary
MaturityExternal featuresExternal featuresHistological features
Stage 1 Immature virgins Long, slender and thread like translucent structures occupying 33% of the abdominal cavity. Long, slender and thread like structures, red in color and occupying 33% of the abdominal cavity Largest oocytes have a maximum diameter of 25 μ m. Many oocytes have small nucleus relative to the size of the thick staining cytoplasm. Ovary wall is 53 μ m thick 
Stage 2a Developing virgins Ribbon like structures slightly bigger than 1, grayish-whitish in color and occupy 50% of the abdominal cavity. Firm and ribbon like slight increase in size, pink in color and occupy 50% of the abdominal cavity, oocytes are discernable. Largest oocytes have maximum diameter of 54 μ m. large circular nucleus. Oocytes have no definite shape. ovary wall is 85 μ m thick 
Stage 2b Recovering Same as those in 2a but slightly bigger and firmer. Same as those in 2a but softer and plump to the touch Same as stage 2a except for the many residual atretic oocytes. 
Stage 3 Maturing Broad and thick, dark white color blood vessels visible externally and milt oozes out from cut surface. Occupying 70% of the abdominal surface. Broad and thick occupying 70% of the abdominal cavity red or reddish brown. Blood vessels visible externallyand. oocytes visible though ovary wall. Largest oocytes have a diameter of 91 μ m. Many oocytes with cytoplasmic vacuoles present. Oocytes are contained in well organized ovigerous lamellae, and ovary wall is 200 μ m. 
Stage 4 Ripe Further increase in size occupying 90% of the abdominal cavity. White in color. Milt oozes out on slight pressure. Distended and occupying 90% of the abdominal cavity Blood vessel disappearing and oocytes can be seen clearly through the ovary wall. Largest oocyte has a diameter of 109 μ m. Many oocytes with cytoplasmic vacuoles still present. Largest oocytes are filled with eosinophilic yolk granules. Ovigerous lamellae present but some disappearing. 
Stage 5 Running Fully distended occupying almost all the abdominal cavity exudes milt on slight pressure. Fully distended with granular surface occupying all of the abdominal cavity Largest oocytes have a maximum diameter of 121 μ m. Many oocytes have thickly staining yolk granules. Some late oocytes have oil globules in the cytoplasm. 
Stage 6 Spent Shrunken and flaccid, walls are harder and wrinkled. No milt oozes out on pressure and blood vessels are visible externally. Ovary is not fully empty. Residual oocytes present. Flaccid and red in color. Ovary wall is thick. Largest oocytes have a maximum diameter of 95 μ m. Smaller oocytes have thickly stained cytoplasm. Numerous blood vessels at the periphery of the residual oocytes. Post ovulatory follicles present. 
TestesOvaryOvary
MaturityExternal featuresExternal featuresHistological features
Stage 1 Immature virgins Long, slender and thread like translucent structures occupying 33% of the abdominal cavity. Long, slender and thread like structures, red in color and occupying 33% of the abdominal cavity Largest oocytes have a maximum diameter of 25 μ m. Many oocytes have small nucleus relative to the size of the thick staining cytoplasm. Ovary wall is 53 μ m thick 
Stage 2a Developing virgins Ribbon like structures slightly bigger than 1, grayish-whitish in color and occupy 50% of the abdominal cavity. Firm and ribbon like slight increase in size, pink in color and occupy 50% of the abdominal cavity, oocytes are discernable. Largest oocytes have maximum diameter of 54 μ m. large circular nucleus. Oocytes have no definite shape. ovary wall is 85 μ m thick 
Stage 2b Recovering Same as those in 2a but slightly bigger and firmer. Same as those in 2a but softer and plump to the touch Same as stage 2a except for the many residual atretic oocytes. 
Stage 3 Maturing Broad and thick, dark white color blood vessels visible externally and milt oozes out from cut surface. Occupying 70% of the abdominal surface. Broad and thick occupying 70% of the abdominal cavity red or reddish brown. Blood vessels visible externallyand. oocytes visible though ovary wall. Largest oocytes have a diameter of 91 μ m. Many oocytes with cytoplasmic vacuoles present. Oocytes are contained in well organized ovigerous lamellae, and ovary wall is 200 μ m. 
Stage 4 Ripe Further increase in size occupying 90% of the abdominal cavity. White in color. Milt oozes out on slight pressure. Distended and occupying 90% of the abdominal cavity Blood vessel disappearing and oocytes can be seen clearly through the ovary wall. Largest oocyte has a diameter of 109 μ m. Many oocytes with cytoplasmic vacuoles still present. Largest oocytes are filled with eosinophilic yolk granules. Ovigerous lamellae present but some disappearing. 
Stage 5 Running Fully distended occupying almost all the abdominal cavity exudes milt on slight pressure. Fully distended with granular surface occupying all of the abdominal cavity Largest oocytes have a maximum diameter of 121 μ m. Many oocytes have thickly staining yolk granules. Some late oocytes have oil globules in the cytoplasm. 
Stage 6 Spent Shrunken and flaccid, walls are harder and wrinkled. No milt oozes out on pressure and blood vessels are visible externally. Ovary is not fully empty. Residual oocytes present. Flaccid and red in color. Ovary wall is thick. Largest oocytes have a maximum diameter of 95 μ m. Smaller oocytes have thickly stained cytoplasm. Numerous blood vessels at the periphery of the residual oocytes. Post ovulatory follicles present. 
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