Bighead carp (Hypophthalmichthys nobilis) is a key aquaculture species, with the head and its orbital fat being a commercially valuable product. To elucidate the molecular basis of growth variation, we performed comparative transcriptome analysis of orbital fat from extreme growth phenotypes at juvenile (6 months) and market-size (18 months) stages. In juveniles, slow growth was linked to upregulation of stress-responsive genes (sgk1, fkbp5, lipg), while fast growth correlated with higher expression of stress-buffering (crhbp) and nutrient-signaling (rbp2, mgea5) genes. At 18 months, divergent growth aligned with opposing lipid metabolic states: a pro-anabolic profile (dgat2, fads2) supported fast growth, whereas a catabolic profile (cpt1b, ppargc1a) was associated with slow growth. These results demonstrate stage-specific transcriptional reprogramming in orbital fat underlying growth variation. This study provides a molecular framework for orbital fat-mediated growth regulation and highlights potential candidate genes for molecular breeding in bighead carp.

In this work, an electrochemical sensor based on a Fe₃O₄/STAB/chitosan nanocomposite was developed for the detection of nitrite. The nanocomposite exhibited positive charges on its surface, high conductivity, favorable biocompatibility, and strong antifouling ability, enabling electrostatic adsorption of nitrite and thereby enhancing detection sensitivity. A glassy carbon electrode (GCE) modified with this material was employed for nitrite measurement using differential pulse voltammetry (DPV). Under optimized conditions, the Fe₃O₄/STAB/chitosan/GCE showed excellent analytical performance for nitrite detection, with a detection limit of 0.151 mg/L. Recovery rates of nitrite in real samples ranged from 95.02% to 107.93%, with relative standard deviations between 0.91% and 5.23%. Moreover, the modified GCE displayed excellent selectivity, reproducibility, and repeatability for nitrite detection. Therefore, this work provides a novel strategy for nitrite monitoring in aquaculture.