Abstract:
Opsariichthys uncirostris is a small, omnivorous freshwater fish with slightly predatory behavior. It has diverged into two subspecies,
O. uncirostris amurensis (northern China) and
O. uncirostris bidens (southern China), with distinct physiological adaptations to their respective northern and southern geographic climates.
O. uncirostris amurensis is characterized by a shorter maturation cycle (precocious maturity), whereas
O. uncirostris bidens exhibits faster growth rates. With the growing consumer demand for stream fish, aquaculture production has intensified. However, this has led to increased inbreeding, resulting in declining seed quality and disease resistance, which has impeded sustainable industry development. To address this issue, there is an urgent need to develop new strains with superior traits. This study aimed to conduct a comparative morphological analysis of these two subspecies and perform a diallel cross to evaluate heterosis in embryonic development, larval viability, and growth performance. The ultimate goal was to produce a novel hybrid strain that outperforms both parental lines, providing a genetically improved stock to support the high-quality development of the industry. In this study, we measured morphological trait indices of
O.
uncirostris bidens (Minjiang River Population) and
O.
uncirostris amurensis (Songhua River Population). Through path and correlation analyses, the influence of each trait on body weight, and the embryonic development and growth of the offspring of the complete diallel crossing between two populations were evaluated and analyzed. Morphological quantifiable trait analysis showed that the morphological differences between different genders in the two populations of
O.
uncirostris amurensis and
O.
uncirostris bidens were mainly concentrated in aspects such as the overall contour of the fish body, head shape, and fish body size. Among them, the TRL/BL standardized index of female
O.
uncirostris amurensis was the largest (0.47 ± 0.02). The PFL/BL standardized index of male
O.
uncirostris bidens was the largest (0.18 ± 0.01). Stepwise discriminant analysis identified 10 significant traits, leading to a discriminant equation with an overall accuracy rate of 98.33% to distinguish the two populations (
F = 38.881
X1 - 53.252
X2 - 59.503
X3 - 7.545
X4 + 22.466
X5 + 22.387
X6 - 20.866
X7 - 0.306
X8 + 0.228
X9 + 0.376
X10 - 6.082). Correlation analysis showed that the 17 growth traits of the two groups were positively correlated with body weight. Path analysis showed that, the correlation coefficient between body weight and body thickness was the largest (0.93). In
O. uncirostris amurensis, the correlation coefficient between total length and body weight was the largest (0.92). Embryonic development times for offspring from shortest to longest were as follows: self-crossed progeny of
O. uncirostris bidens (SS, 37 h 28 min), progeny of
O.
uncirostris bidens male ×
O.
uncirostris amurensis female (SN, 38 h 6 min), progeny of
O.
uncirostris amurensis male ×
O.
uncirostris bidens female (NS, 40 h 57 min), and self-crossed progeny of
O.
uncirostris amurensis (SS, 42 h 8 min). Analysis of the growth differences and mid-parent heterosis of the complete diallel crossing progeny showed the progeny of NS group hybrids exhibited heterosis in body weight and total length at 30, 60, and 90 days after hatching, with superior parent heterosis observed at 30 and 60 days after hatching. The SN group hybrid progeny showed mid-parent heterosis for body weight at 90 days after hatching. The study demonstrated the hybridization between the Minjiang River population of
O.
uncirostris bidens and the Songhua River population of
O.
uncirostris amurensis has certain heterosis , providing a valuable reference for a new breed development.
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