The formation and growth characteristics of a novel allotriploid fish

Triploid fish are highly valued in aquaculture for their rapid growth and sterility. In this study, a novel allotriploid fish (3nWC, 3n = 150) was obtained through an inter-ploidy cross between diploid hybrid crucian carp (WR-II, 2n = 100, ♀) and autotetraploid carp (4nNC, 4n = 200, ♂). The chromosome numbers, morphological traits, gonadal development, growth rates, muscle fibers, muscle nutrition, intestinal structure, and the transcript levels of growth-related genes in 3nWC were examined. Fertility and hatchability rates of the hybrid crosses reached 94.62% and 86.37%, respectively, demonstrating its potential for large-scale breeding applications; 3nWC is an allotriploid fish with 150 chromosomes; 3nWC exhibits morphological characteristics that are intermediate between parents; the ovaries and testis of 3nWC exhibited stagnation and degenerative changes, leading to gonadal sterility; a marked enrichment of essential amino acids (EAA) and total essential amino acids (TAA) was detected in the muscle of triploid 3nWC relative to its diploid parent red crucian carp ( Carassius auratus red var., RCC; 2n = 100). Furthermore, 3nWC exhibited faster growth, muscle hypertrophy, muscle hyperplasia, and greater fold height and goblet cell density compared to its parents. Finally, the transcript levels of growth-related genes, such as pituitary adenylate cyclase-activating polypeptide ( pacap ), myogenin ( myog ), and growth hormone ( gh ), exhibited significantly increased levels in 3nWC. The creation of this novel allotriploid is of great significance to the study of fish genetic breeding and fish growth characteristics. • A novel allotriploid fish (3nWC) derived from inter-ploidy crossing of diploid and tetraploid fish. • 3nWC show gonadal sterility in both sexes. • 3nWC showed positive advantages in growth, muscle fibers, muscle nutrition and gut structure. • 3nWC is important for the study of fish genetic breeding and growth characteristics.