Using triploid-tetraploid technology for oyster production
When it comes to oyster seed production, the triploid-tetraploid technology is the option that delivers. But verification on different stages and facets are necessary to make it work.
"Accurate ploidy determination is absolutely required for the application of this technology," said Huiping Yang et al, of the IFAS Extension - University of Florida, in Production and Performance of Triploid Oysters for Aquaculture.
"Ploidy verification of broodstock before spawning can ensure that hatchery efforts are carried out as planned. Ploidy confirmation of larvae at swimming stage can ensure early detection of possible polyploid outcome. And ploidy validation of seed labeled as triploids before shipment can ensure that no mishandling occurred during the larval and seed rearing process."
The establishment of tetraploid breeding stocks is integral to 100 percent triploid seed production of triploid oyster.
"Commercial triploid oysters are typically produced by crossing tetraploids with normal diploids to yield 100 percent triploid seed. This approach allows for implementation by commercial hatchery operations and has supported oyster farming operations throughout the world," they said.
The other method of producing triploids involves inhibiting the release of polar bodies I or II. It is not commonly used for commercial triploid seed production, it was explained, because of several downsides.
Production of 100 percent triploid offspring is rarely achieved. Triploid survival is also lower than larval survival in other groups. Chemicals used to inhibit polar bodies may be a threat to human health.
Oysters normally spawn in spring and fall and after spawning, especially in summer, diploid is thin, watery and considered unpalatable. Triploid, considered sterile with poor gonad development, retains its superior meat quality throughout the year and, thus, meets the year-round demand.
It has more to offer on top of this.
Compared to diploid, triploid demonstrated much better performance indicators in juvenile and adult stages in almost all of the studied shellfish species.
The superior growth of triploids in almost all oyster species studied was confirmed at the adult stage, when a study reported a growth rate that was192 percent faster than diploids. In some cases, it was even faster because of selective breeding of tetraploid broodstock.
The authors stressed that environmental factors can also affect growth and survival of triploid oysters.
At present, triploid Pacific oyster accounts for about 50 percent of the production on the U.S. West Coast and nearly 100 percent of the seed production in the Chesapeake Bay.
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