Ploidy and growth performance of hybrid progeny between tetraploid Misgurnus anguillicaudatus and Paramisgurnus dabryanus.

Experimental crossings were made between tetraploid loach ( Misgurnus anguillicaudatus, T for short) and diploid large-scale loach ( Paramisgurnus dabryanus, P for short), resulting in T×T, T×P and P×P crosses (female before male). Meanwhile, a part of T×P cross was cold shocked to inhibit second meiosis (T×P-0 for short). Fertility rate, hatching rate and survival rate of T×T, T×P, P×P and T×P-0 were measured. Flow cytometry and chromosome count were taken to identify ploidy statuses of the four crosses. Results showed that T×T, T×P and P×P were, respectively, tetraploidy (4n = 100), triploidy (3n = 74) and diplody (2n = 48), while 89.19 per cent of T×P-0 of 12 months old were pentaploidy (5n = 124, T×P-0-5n for short) and the others were triploidy. Morphological data of the four crosses of 12 months old showed that morphological characteristics of T×P and T×P-0-5n loach were between those of their parents, while T×P-0-5n loach presented a smallest head length/body length. Total lengths of T×P and T×P-0-5n were significantly larger than those of T×T and P×P, showing hybrid vigour. This study will provide valuable information for production of polyploidy loach and breeding programmes of the two loaches and other closely related species. [ABSTRACT FROM AUTHOR]