# The Formation of a Novel Intergeneric Hybrid Fish Derived from Megalobrama amblycephala (♀) × Culter dabryi (♂)

## TL;DR

Scientists created a new hybrid fish by combining two species, which grows faster, is fertile, and has better nutrition than its parents.

## Contribution

The study introduces a novel intergeneric hybrid fish with superior growth, fertility, and nutritional traits.

## Key findings

- The hybrid fish (BG) is diploid with 48 chromosomes and predominantly inherits genetic traits from the maternal species.
- BG has 1.81 times the body weight of the green tip culter and exhibits accelerated spermatogenesis.
- BG muscle contains higher crude protein and umami amino acids compared to its parent species.

## Abstract

In this study, we successfully developed a novel hybrid fish (BG) based on distant hybridization between blunt snout bream (BSB, ♀) and green tip culter (GTC, ♂). Genetic characterization confirmed that BG was diploid (2n = 48), exhibiting predominantly maternal (BSB) genetic inheritance with the incorporation of specific paternal (GTC) genomic fragments. BG demonstrated a significantly higher body weight, reaching approximately 1.81-fold that of the GTC. Additionally, it possessed bisexual fertility and accelerated spermatogenesis compared to BSB. Nutritional analyses demonstrated that BG contained a higher crude protein content, increased levels of umami amino acids, and greater concentrations of beneficial polyunsaturated fatty acids than its parents. Collectively, these results indicate that BG combines superior growth performance, reproductive characteristics, and nutritional qualities, establishing its significant potential as an advantageous germplasm resource for aquaculture breeding programs.

Distant hybridization in fish serves to integrate the genetic material from two distinct, distantly related species. In this study, we successfully produced a new hybrid fish (BG) through the intergeneric hybridization of blunt snout bream (Megalobrama amblycephala, BSB, 2n = 48, ♀) and green tip culter (Culter dabryi, GTC, 2n = 48, ♂). The objective of this research was to characterize the genetic, morphological, reproductive, and nutritional features of the hybrid compared with its parents. The DNA content and chromosomal number analysis revealed that BG was a diploid hybrid fish with 48 chromosomes. Integrated analysis of 5S rDNA, mitochondrial DNA, and Sox9 gene sequences revealed that BG predominantly inherited its genetic traits from BSB. Notably, certain gene fragments (376 bp segment of 5S rDNA class II and 718 bp segment of BG Sox9-II) originated from the paternal GTC, demonstrating biparental genomic integration. The growth performance analysis revealed that BG exhibited enhanced growth, achieving a body weight significantly greater than that of BSB and 1.81-fold that of GTC (both p < 0.05). The reproductive analysis indicated that BG possessed bisexual fertility, with testicular histology revealing accelerated spermatogenesis relative to BSB. Additionally, the nutritional analysis of BG muscle revealed elevated levels of crude protein (18.13%) and umami amino acids (5.45%) compared to those in its parents. BG showed higher growth, bisexual fertility, and improved muscle nutritional composition. This hybrid represents a promising resource for cyprinid breeding and aquaculture diversification.