Evidence for the Growth Superiority and Delayed Ovarian Development in Tetraploid Loach Misgurnus anguillicaudatus

The diploids and tetraploids of cyprinid loach Misgurnus anguillicaudatus coexist in many natural habits. The tetraploids generally exhibit superior growth performance and delayed gonadal development compared with diploids. To investigate the regulation mechanism of growth superiority and ovarian development in tetraploids, we first conducted a long-term culture experiment and histological observation. The tetraploids exhibited a higher growth performance and delayed ovarian development. Meanwhile, at a genetic level, an average of 6891 differentially expressed genes (DEGs) between diploids and tetraploids were identified from the brain, pituitary, liver, gonad and muscle using the RNA-seq method. Among these DEGs, as expected, some candidate genes, including IGF family genes, somatostatin, leptin, cyp19a1b, gth alpha, lh beta and fsh beta, were detected, which play critical roles in the regulation of growth and gonad development of fish. In particular, the genes related to GH/IGF axis and growth factors, signal transduction, gonadal hormone and appetite were significantly increased in tetraploids. The clustering analyses of the key candidate genes showed that most key genes were up-regulated in the pituitary and gonad of tetraploids instead of other tissues. The dynamics of these key genes provide valuable genetic evidence for clarifying the growth superiority and delayed gonadal development of tetraploids. Moreover, this study also provides some clues for unveiling the genetic superiority of polyploidy species in other phenotypes.

Automated summary

In this study, the coexistence of diploids and tetraploids in the cyprinid loach was investigated. The tetraploids showed superior growth performance and delayed ovarian development compared to diploids. At the genetic level, numerous differentially expressed genes were identified between diploids and tetraploids, including candidate genes involved in growth and gonad development regulation. The up-regulation of key candidate genes was particularly prominent in the pituitary and gonad of tetraploids. Overall, this study provides valuable genetic evidence for understanding the growth superiority and delayed gonadal development of tetraploids, as well as insights into the genetic superiority of polyploidy species in other phenotypes.