Meiotic maturation and progeny of oocytes from triploid Japanese pearl oysters ( Pinctada fucata martensii) fertilized with spermatozoa from diploids

Abstract

Oocytes from two female triploid pearl oysters were fertilized with spermatozoa from one diploid male (3n × 2n cross) to observe meiotic maturation in the eggs and the resultant larvae and juveniles. Meiosis and development up to the 4-cell stage was virtually identical to that in the diploid control. Karyotype analysis of 6-h-old larvae revealed high 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 × 10 −2% and 7.5 × 10 −2%) compared with those in the control (1.9% and 5.1%), and only diploid and triploid progeny were found at this stage. These results suggest that aneuploids in the 3n × 2n cross died during the larval stage and only euploid juveniles survived up to 4 months.