Cyprinid fishes are the most sustainable human food production in aquaculture. However, these fishes in other aquatic systems may contribute to ecological disruption due to their potential as “invasive” species. Polyploidy and distant hybridization are creative genetic tools to establish improvements in growth performance and production efficiency but can also serve conservation goals and act as barriers (sterility) to protect wild fish stocks and their diversity. In other words, these methods are not serving exclusive or opposite research targets but are rather complimentary technologies. Triploidy is recognized and currently utilized as a major tool to eliminate concerns of unintentional release of domesticated fish and to protect the genetic heritage of wild stocks. However, induced triploidy via application of physical shocks also results in high frequency of skeletal deformities and low viability. Therefore, production of meiotic-shock-induced triploids involves inferior survival, compromised marketability (deformities) and significant cost stemming from needs of (individual) confirmation of sterility (polyploidy). Alternatively, crossing diploid and induced tetraploid individuals yields biological triploids that do not undergo physical shocks and thus eliminates the inferior characteristics of induced triploids. In addition, establishment of tetraploid broodstock lines has biological, ethical, and financial incentives.
Tetraploid cyprinids hybrids (goldfish female x common carp male) were obtained (1) by crossing diploid somatic hybrids producing diploid gametes, or (2) by crossing triploid hybrid females with common carp males. We explored the possibility that common carp diploid females fertilized with hybrid producing diploid sperm and progeny subjected to physical shock will result in tetraploidization. Initial outcome of this experiment was highly encouraging as larval stage from this procedure were almost exclusively tetraploids or mosaics (Fig. 1). However, surviving juveniles (4 months old) were confirmed by flow cytometry mostly diploids. We continue to grow this batch of fish and the next generation (diploid gametes) might prove to be the founder of tetraploid linage.