BYSSUS GROWTH IN WINGED PEARL OYSTER PTERIA PENGUIN (RODING, 1798)

Relationships between shell morphological traits and byssus dimensions in adult winged pearl oysters Pteria penguin are described to include a more detailed description of byssus growth in juveniles under typical culture conditions. Byssus growth, byssus diameter (BD) relations between the byssus and shell traits [shell height; total wet weight (TW)], byssus occurrence, and the size distributions in samples collected monthly or bimonthly over a 1-y duration were recorded. Pearl oysters exhibited continuous shell growth and weight increase over the experimental period, but byssal measurements exhibited a different pattern. The increase in BD decreased as oysters aged and no further increase was observed after day 267. Moreover, BD/TW ratio exhibited a steadily diminishing trend as P. penguin aged. The relationships between the BD and the shell traits in 68-day-old oysters proved to be insignificant, probably because the oysters were neither heavy nor large enough to exhibit the relationships, but later, when oysters increased in size and weight, the relationships became significant. Byssus diameter was determined to be slightly more closely related to the weight of the animal than the size of the shell, and oysters at day 183 exhibited comparatively higher r(2) values than oysters at day 366 of cultivation. The occurrence of oysters without byssus decreased gradually during cultivation from 30% initially to 0 after a year of cultivation.