FEFU scientists have developed a technique for producing a sustainable population of triploid oysters

The technology for the creation of a stable population of triploid oysters has been developed by scientists at the FEFU Institute of the World Ocean. Through their efforts, the specialists have achieved a 50% survival rate for young triploid oyster larvae, compared to only 30% under normal conditions. This breakthrough has been achieved through the implementation of a new method that has been successfully tested at the Dalstam-Marine Company. This innovative approach has allowed for the cultivation of oysters with an average body weight 82.9% higher than that of diploid oysters. The project was supported by the government's Priority 2030 programme, which aims to promote scientific research and innovation in the field of marine biology. The biologists focused on triploid oysters, which have three sets of chromosomes. This allows them to direct all their energy to growth and mass development rather than reproduction. This unique characteristic enhances their survival rate and ensures the preservation of their commercial value throughout the year.

Triploid oysters can be produced by chemical and physical methods or by crossing tetraploid males with diploid females. The high commercial cost and toxicity of chemical agents limit their use in producing triploids. While the method of crossing tetraploids with diploids can be effective in terms of commercial benefits, it poses significant environmental risks due to the potential for sterilising natural populations of Pacific oysters. Therefore, physical techniques, such as heat shock, which are less costly and environmentally friendly, are increasingly being used to control chromosome sets in bivalves.

FEFU scientists conducted an experiment on the thermal induction of triploidy in Pacific oysters and tested various methods for determining ploidy. For the first time in Far Eastern aquaculture practice, specialists employed the method of thermally inducing organismic polyploidy in Crassostrea gigas, a Pacific oyster species. This involves a brief change in water temperature in a container containing fertilized oocytes. The scientists evaluated the effectiveness of this method, monitoring the survival and development of the larvae, as well as the growth and development of the oyster under real production conditions at Dalstam-Marin. The overall survival rate of triploid larvae was found to be 2.4 times higher than that of diploid larvae after 22 months of cultivation. At this point, 80.9% of the triploids had reached commercial size, compared to only 57.9% of the diploids. The average weight of the triploid oysters after 24 months of cultivation was found to be 124.6 ± 2.7 grams, which is a 43% increase compared to the weight of the diploid oysters.

"The known fact that triploids of the Pacific oyster triploids exhibit faster growth and achieve a greater mass compared to normal diploid individuals. This highlights the need for the development and implementation of safe biotechnological methods in mariculture practices. This research has highlighted the prospect of using short-term temperature effects on fertilised oocytes to produce triploid oysters for commercial purposes", said Anna Anisimova, PhD in Biological Sciences, Associate Professor of the Department of Cell Biology and Genetics at the FEFU Institute of the World Ocean.

At the same time, the oysters have fully retained their nutritional value and taste qualities. The scientists note that the effectiveness of the technology depends on the type of exposure chosen during the experiment. They plan to continue this research in order to optimise it, which is of important practical interest for regional aquaculture. This approach doesn’t involve genetic modification and is therefore completely safe for consumers.

As part of the "Technologies for Monitoring the Health Status and Improving Growth Rates of Aquaculture Facilities" project under the Priority-2030 Program, biologists are investigating the causes of diseases and developing preventive measures for valuable aquatic species such as trepang, scallops, mussels, crabs, and other marine organisms. In industrial aquaculture settings, these organisms live in crowded conditions, so outbreaks of infection can quickly lead to massive mortality, causing significant losses to businesses. By 2030, it is planned to establish a pilot production of probiotic dietary supplements for shellfish as well as to develop a range of methods for genomic breeding and rapid diagnosis of infectious diseases in commercially significant aquatic species.