Histological examination of gametogenesis in genetic triploid Crassostrea ariakensis in Chesapeake Bay

Combating the loss of the oyster resource in Chesapeake Bay has been ongoing for decades. Focus has turned recently to the non-native Suminoe oyster, Crassostrea ariakensis and the possibility of its introduction as reproducing diploid or a triploid for aquaculture only. In field tests, triploid C. ariakensis has exhibited high survival, growth, and disease tolerance in Chesapeake Bay. As reported for several other shellfish species, triploidy often results in abnormal or arrested gametogenesis. Documenting the extent of gamete development in triploid C. ariakensis is an important biological variable addressing the risk associated with non-native introduction. Nine diploid females and one tetraploid male were used as parents for this triploid spawn. These genetic triploids were deployed at six sites along Chesapeake Bay ranging from low salinity ( similar to 13ppt) to high salinity ( similar to 35ppt). Diploid native controls were sampled at each site to track the "normal" cycle of gametogenesis. Paraffin histology of triploids revealed abnormal gamete production typical of triploid. However, a few sites produced unusually mature ova and spermatozoa for triploids. Samples late in the season indicated spawning had occurred in both diploid and triploid males and females.