Heteroploid mosaic tetraploids of Crassostrea virginica produce normal triploid larvae and juveniles as revealed by flow cytometry

Autotetraploid Pacific oysters (Crassostrea gigas) obtained using normal diploid eggs: induction and impact on cytogenetic stability

“…low cytogenetic stability of tetraploids originating from the TrD+PB1 method fully agree with the recently published results concerning tetraploids from C. gigas (Zhang et al 2014a,b) and C. virginica (Matt and Allen 2014), which were inducted using the same method. In these studies, the majority of oysters initially identified as being tetraploids are no longer so during the course of their development, with the emergence of a high proportion of mosaic and aneuploid oysters.…”

“…This notably explains the fact that, in these studies, many oysters identified by flow cytometry as being "tetraploids" were discovered to be in reality aneuploids. In agreement with the results of Zhang et al (2014a), and in disagreement with those published by Matt and Allen (2014), our results show that the individual mosaics, so identified in our work by the two detection methods, all presented gills with different percentages of eutetraploid cells (with 40 chromosomes) and cells that were most often aneuploid (hypo-tetraploid, hypo/hyper-triploid, hyper-diploid). The simultaneous presence of both eutetraploid cells and aneuploid cells does not fit with an explanation of the reversion being due to the total loss of one or several sets of chromosomes, but rather reinforces the idea that the reversion is a gradual phenomenon in which the shift from tetraploidy to a more stable state occurs via a progressive loss of chromosomes during the successive mitotic divisions.…”

“…Thus, with the aging of individuals, and across generations, it appears to be particularly difficult for these tetraploids to maintain their genetic stability as pure biotypes or broodstocks. Finally, although tetraploids faithfully make tetraploids when crossed with themselves and triploids when crossed with diploids, they also frequently produced offspring which were not of the desired ploidy class and/or which were of lower biological performances Allen et al, 1999;Hand et al, 1999;Mc-Combie et al 2005b;Guo et al 2009;Zhang et al 2010a, Zhang et al 2010b, Zhang et al 2014aZhang et al 2014b;Matt and Allen 2014). Thus, producing new tetraploids directly from diploids without the use of any genetic material from triploids would be a significant improvement.…”

“…It represents also a serious commercial challenge on account of tetraploids being used as genitors for the commercial production of all-triploids (Zhang et al 2010a,b;Matt and Allen 2014). The aneuploidies and reversions observed in tetraploids can thus have serious consequences for both the sustainability of tetraploid broodstock itself as well as their triploid offspring, whose cytogenetic quality, and hence zootechnical performance, can no longer be guaranteed.…”

Incomplete sterility of hybrids produced byCrassostrea hongkongensisfemale × Crassostrea gigasmale crosses

“…Furthermore, this study presented three points regarding incomplete sterile hybrids for oyster farming and breeding. First, a high degree of sterility in hybrids, such as in a triploid oyster, can prevent the diversion of energy towards reproduction development during the mature stage, allowing the organism to maintain good meat quality for the market year‐round, which is a solution to the problem of poor meat quality in diploid species during the reproductive stage (Nell ; Ahmed, Koike, Strüssmann, Yamasaki, Yokota & Watanabe ; Guo ; Piferrer, Beaumont, Falguière, Flajšhans, Haffray & Colombo ; Matt & Allen ; Weber, Hostuttler, Cleveland & Leeds ). Second, these sterile hybrids can avoid causing reproductive contamination or genetic contamination to local oyster populations, allowing them to maintain their biodiversity (Guo & Allen ,b, ; Ibarra, Hernández‐Ibarra, Cruz, Pérez‐Enríquez, Ávila & Ramírez ; Thresher, Grewe, Patil, Whyard, Templeton, Chaimongol, Hardy, Hinds & Dunham ).…”