MEIOTIC MATURATION AND PROGENY OF OOCYTES FROM TRIPLOID JAPANESE PEARL OYSTERS (PINCTADA-FUCATA-MARTENSII) FERTILIZED WITH SPERMATOZOA FROMDIPLOIDS

Oocytes from two female triploid pearl oysters were fertilized with sp ermatozoa from one diploid male (3n X 2n cross) to observe meiotic mat uration in the eggs and the resultant larvae and juveniles. Meiosis an d development up to the 4-cell stage was virtually identical to that i n the diploid control. Karyotype analysis of 6-h-old larvae revealed h igh levels of aneuploidy and a broad distribution of chromosome number (21-59 with a mode of 32-34) while control larvae exhibited a diploid chromosome number of 28. Veliger larvae at 21 h were highly abnormal (82.2% and 92.2%). Survival to 4 months was very low (5.8 x 10(-2)% an d 7.5 x 10(-2)%) compared with those in the control (1.9% and 5.1%), a nd only diploid and triploid progeny were found at this stage. These r esults suggest that aneuploids in the 3n x 2n cross died during the la rval stage and only euploid juveniles survived up to 4 months.