Temporal analysis of pikeperch (Sander lucioperca) under heat stress: an integrated study from histological, physiological and transcriptomic perspectives.

Global warming has a significant impact on fish physiology and behavior. As the primary site for nutrient digestion and absorption, the intestine is particularly vulnerable to metabolic disruption under heat stress. However, the intestinal response mechanisms of pikeperch under such conditions remain poorly understood. In this study, we combined histological analysis, enzyme activity assays, and transcriptomics to explore the time-dependent dynamic response of the pikeperch intestine to heat stress. Intestinal histopathological analysis revealed a significant increase in goblet cell numbers at 3 h. This was followed by blurred villus borders and tissue vacuolization at 6 h, and further progression to dilated central lacteal gaps and a vacuolated lamina propria by 12 h. The Malondialdehyde (MDA) was significantly up-regulated at 6 h post-heat stress, then slightly decreased at 12 h. Furthermore, the antioxidant enzymes including peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT), all showed a transient increase, peaking before declining. This physiological timeline was corroborated by transcriptional profiling, which uncovered a coordinated response initiating with metabolic dysregulation (3 h), transitioning through oxidative stress and cell fate commitment (6 h), and culminating in repair and immune processes (12 h). Our study not only filled a research gap regarding the intestinal response of pikeperch to heat stress but also provided a theoretical framework for supporting the healthy aquaculture of this species.