Performance of Tripfoid Pacific Oysters, Crassostrea gigas: Gametogenesis

Abstract

Triploid Pacific oysters, Crassostrea gigas, were produced by treating newly fertilized eggs with cytochalasin B. After a year of growth, diploid and triploid oysters were sampled throughout the reproductive season to determine the effect of triploidy on gamete formation and sexual expression. Relative to diploids, gametogenesis in triploids was retarded but not absent: both male and female triploids produced some gonad. Gametogenesis in most triploid males resulted in spermatid production; all triploid males produced numerous spermatocytes. Oocyte formation in most triploid females was severely retarded, although some triploid females produced numerous eggs. Hermaphroditism in the triploid population was markedly higher than in diploids: 29 versus 1%, respectively. The ratio of males:females was the same in diploids and triploids.

Responses of diploid and triploid Pacific oysters Crassostrea gigas to Vibrio infection in relation to their reproductive status

“…This result was not repeated on the other dates, suggesting that triploid oysters might have reduced resistance during the reproductive period, possibly due to some sort of reproductive cost. This hypothesis is supported by the fact that histological analysis revealed a significant development of gonadic tissue in both triploid groups, indicating a significant allocation to reproduction in these individuals, as reported in some previous studies (Allen and Downing, 1990;Normand et al, 2009). Additionally, it is probable that the measurements of gonadic occupation did not fully reflect the amount of energy devoted to reproduction in triploid oysters, notably because they have the tendency to resorb reproductive tissue before reaching full maturity (Allen and Downing, 1990;Normand et al, 2008;Shpigel et al, 1992).…”

“…Knowing that such reproductive tissue degeneration processes are far more common in triploid than in diploid oysters (Allen and Downing, 1990;Shpigel et al, 1992), the disturbed reproductive tissue development in triploid oysters might result in some additional underestimated costs. It appears difficult in this context to precisely estimate the energetic allocation to reproduction in triploid individuals, a practical problem that was already pointed out in a previous study .…”

Comparative studies of the growth, survival, and reproduction of diploid and triploid Kumamoto oyster, Crassostrea sikamea

“…The reproductive stage was determined through qualitative classification of the five stages described by Allen and Downing () with modifications made by Cox, Smith, Nell, and Maguire (): early development, late development, mature, spawning, and spent. Early development is defined as the beginning of gamete formation.…”

Seasonal variation of the glycogen enzyme activity in diploid and triploid Pacific oyster gonad during sexual maturation

“…In accordance with previous studies (Tabarini, 1984;Allen and Downing, 1986;Akashige and Fushimi, 1992;Utting et al, 1996;Ruiz-Verdugo et al, 2001), we found that glycogen content of triploid oysters was significantly higher than that of diploids during the gametogenesis period. The reasonable explanation is that triploid is sterile (Tabarini, 1984;Allen and Downing, 1986;, and that the higher glycogen content is resulted because a relatively smaller proportion of metabolic flux is directed towards reproductive output (Allen and Downing, 1990; …”