Document Type : Short Communication
Windowpane oyster, Placuna placenta from Sonmiani on the coast of Pakistan was studied. They are pearl producing oysters well-known in south Asia. The sex-ratio in this species was found to be close to 1:1 Mendelian ratio with number of females being slightly greater than males. No sexually undifferentiated and hermaphrodite oyster was found. Five stages of gametogensis, developing, ripe, partially spawned, spent and resorbing were identified in male and female oysters. Spawning in males and females was observed throughout the year with peak in spring and autumn and a brief resting period in winter. Gonad index in males was 1 to 5, whereas, in females ranked 1 to 4. This value was never ranked 5 in females as continuous spawning occurred throughout the year except December.