Phenotypic characteristics of hybrid <scp> F ₁ </scp> of <scp> <i>Opsariichthys bidens</i> </scp> (♀) ×  <scp> <i>Zacco acanthogenys</i> </scp> (♂) and its embryonic, larva–juvenile metamorphosis development

In the present study, an intergeneric cross was conducted between Opsariichthys bidens (♀) and Zacco acanthogenys (♂);the morphological characteristics of the hybrid offspring generation (F₁) were observed and recorded at various periods of the development of the embryos and young larvae; and comparative analyses of the external morphological data of the adult fish and the parameters of their external shape framework were carried out. Results demonstrated that hybrid fertilized eggs maintained at (25 ± 1)°C water temperature completed hatching within 42 h 47 min post-fertilization, requiring an accumulated temperature of 1026.72°C·h. Embryonic development consisted of 7 distinct phases subdivided into 28 developmental stages. Newly hatched larvae exhibited a mean total length (TL) of 5.23 ± 0.06 mm, with complete yolk-sac absorption occurring by 7 days post-hatching (dph). Early developmental growth patterns (0-30 dph) conformed to the quadratic equation: y = 0.02096x² + 0.23443x + 5.6249 (R² = 0.9559), where y represents TL (mm) and x denotes days post-hatching. Morphological analysis revealed that meristic traits of hybrid progeny predominantly aligned with the maternal lineage, whereas morphometric ratios exhibited intermediate values between parental species. Principal component analysis and cluster analysis of morphometric proportions and framework parameters demonstrated closer similarity to maternal characteristics. Linear discriminant analysis confirmed distinct phenotypic differentiation among the three groups (parental species and hybrids).