Dietary administration of tyramine upregulates on immune resistance, carbohydrate metabolism, and biogenic amines in Macrobrachium rosenbergii

Enhancement of immunity and disease resistance in Litopenaeus vannamei through injection of tyramine formulated with polyethylene glycol

This study investigates the prolonged effect of immune disease resistance in Litopenaeus vannamei through the administration of tyramine (TA) formulated with polyethylene glycol (PEG). Facing the challenges of intensive farming, environmental stress, and global climate changes, innovative approaches to improve shrimp health are essential. The research focuses on the role of biogenic amines in stress response and immune regulation, demonstrating that TA, especially when combined with PEG, significantly prolongs immunity and resistance against Vibrio alginolyticus. The experimental design included administering TA, PEG, and TA-PEG, followed by evaluations of immunity, lactate and glucose levels, and immune-related gene expressions. Results showed notable prolonged effects in total hemocyte count, phenoloxidase activity, and phagocytic activity in the TA-PEG group, indicating enhanced immune activation period. Additionally, the expression of prophenoloxidase system-related genes was significantly upregulated in the TA-PEG group. Furthermore, the TA-PEG group exhibited a significantly higher survival rate in a susceptibility test against V. alginolyticus. The results of this study confirm that the combined use of PEG can effectively extend the immunostimulatory duration of TA.

Expression of octopamine/tyramine receptors and immune regulation in Litopenaeus vannamei under acute and chronic thermal stress

This study investigated the impact of hyperthermal (34 °C) and hypothermal (14 °C) stress on the expression of the octopamine/tyramine receptor (LvOA/TA-R) and immune parameters in Litopenaeus vannamei, which is a species critical to the aquaculture industry. Given the sensitivity of aquatic organisms to climate change, understanding the physiological and immune responses of L. vannamei to temperature variations is essential for developing strategies to mitigate adverse effects. This research focuses on the immune response and expression changes of LvOA/TA-R under acute (0.5, 1, and 2 h) and chronic (24, 72, and 168 h) thermal stress conditions. Our findings reveal that thermal stress induces changes in LvOA/TA-R expression and impacts immune responses. Immune parameters such as total haemocyte count, differential haemocyte count, phenoloxidase activity, respiratory bursts, lysozyme activity, clearance efficiency, and phagocytosis exhibited a general trend of significant decline under the stress conditions. LvOA/TA-R had a higher expression in haemocyte under hyperthermal stress. The study elucidated that thermal stress modifies the expression of the LvOA/TA-R and diminishes immune functionality in L. vannamei, underscoring the potential influence of climate change on industry.

The immunostimulatory effects of Theobroma cacao L. pod husk extract via injection and dietary administrations on Macrobrachium rosenbergii and its resistance against Lactococcus garvieae

The extract from Theobroma cacao L, pod husk served as the immunostimulant to enhance the immunity and resistance against Lactococcus garvieae of Macrobrachium rosenbergii. In this study, we employed the injection method and dietary administration method to determine the effect of cocoa pod husk (CPH) on M. rosenbergii. The non-specific immune parameters and disease resistance were evaluated after the prawn injected with 1 μg prawn^-1 CPH extract (C1), 3 μg prawn^-1 CPH extract (C3), and 5 μg prawn^-1 CPH extract (C5) for 1, 3, and 7 days. The results showed a significant increase of total haemocyte count (THC), differential haemocyte count (DHC), phenoloxidase (PO) activity, respiratory bursts (RBs), and phagocytic activity and clearance efficiency to L. garvieae. The non-specific immune parameters, physiological parameters, and disease resistance and growth performance were evaluated after the prawn fed with 1 g kg^-1 CPH extract diet (CD1), 3 g kg^-1 CPH extract diet (CD3) and 5 g kg^-1 CPH extract diet (CD5). The results showed a significant increase in all immune parameters and showed a significant decrease in physiological parameters. No significant difference was observed in growth performance of prawn fed with the CPH containing diet. Both injection and dietary method showed a significant increase in disease resistance against to L. garvieae. We therefore recommend that CPH extract can be used as a immunostimulant for prawn by dietary administration to regulate immune responses, and carbohydrate metabolism lead to enhance resistance against pathogen.