Physico-immunological Characterizations of Exogenous Substances (Palmitoleic Acid and Okadaic Acid) in Bivalves

Abstract

Abstract

Physico-immunological Characterizations of Exogenous Substances (Palmitoleic Acid and Okadaic Acid) in Bivalves

Chi Cheng Major in Veterinary Pathobiology and Preventive Medicine Department of Veterinary Medicine The Graduate School of Seoul National University

Palmitoleic acid (PA), an algicidal compound, is used against Alexandrium tamarense

however, its impacts on scallops are still unclear. Okadaic acid (OA) is produced by dinoflagellates during harmful algal blooms and is a diarrhetic shellfish poisoning toxin. This study evaluated the effect of harmful algal blooms-related environmental substances on scallops to gain a better understanding of effect of algicide PA and the toxicity of algal toxin OA, and then help improve the intensive breeding and long-term sustainability of scallop farming. Therefore, in the current investigation, various immunological parameters (total hemocyte counts (THC), reactive oxygen species (ROS), malondialdehyde (MDA), glutathione (GSH), lactate dehydrogenase (LDH), and nitric oxide (NO), superoxide dismutase (SOD), acid phosphatase (ACP), alkaline phosphatase (ALP), lysozyme activities, and total protein content) were assessed in the hemolymph of scallops at 3, 6, 12, 24, and 48 h post-exposure (hpe) to different concentrations of PA (20, 40, and 80 mg/L) and OA (50, 100, and 500 nM). Moreover, the expressions of immune-related genes (CLT-6, FREP, HSP90, PGRP, MT, Cu/ZnSOD, MnSOD, PrxV, and BD) were also investigated after exposing bay scallop for 3, 6, 12, 24, and 48 h to any of three different concentrations of PA and OA. Results showed that the lysozyme activity was decreased in scallop treated with PA at 12, 24 and 48 hpe, as compared to control. Although, the SOD activity was higher in all PA treated groups but the significant increment was observed only in 20 mg/L of PA treated group at 12, 24 and 48 hpe. The ACP activities were enhanced from 6–48 hpe in 80 mg/L of PA treated group, as compared to control. The total protein level was enhanced in all the PA treated groups, especially in 40 mg/L of PA treatment group at 3 hpe and in 80 mg/L of PA treatment group at 6, 12, 24 and 48 hpe. THC decreased in PA-treated groups, whereas ALP increased significantly in all of the PA treatment groups at 3 hpe, after which it significantly decreased. The LDH and NO levels were significantly enhanced in the high and medium concentration group. Notably, the GSH level increased in all PA treatment groups at each time interval. Our study also revealed that after treatment with different concentrations of PA, variable effects on the expression of genes involved in the immune system response were observed. Our research demonstrated that immersing scallops in PA may disrupt the endocrine system or immune responses. Therefore, the present study highlights the potential risk of using the PA as an algicide to control algal bloom outbreaks in the marine environment. Moreover, the current investigation revealed the effects of exposure to OA on the immune responses of bay scallop. Results showed that SOD and ACP activities were decreased between 24–48 hpe. The ALP, lysozyme activities, and total protein levels were also modulated after exposure to different concentrations of OA. The ROS, MDA, and NO levels and LDH activity were enhanced after exposure to different concentrations of OA

however, both THC and GSH decreased between 24–48 hpe. The expression of immune-system-related genes was also assessed at different time points during the exposure period. Therefore, these results provide a better understanding of the response status of bivalves against DSP toxins. Overall, our investigation suggest that the exposure to algicide PA and algal toxin OA had negative effects on the antioxidant and non-specific immune responses, and even disrupted the metabolism of bay scallops, making them more vulnerable to environmental stress-inducing agents

Key words: Mollusks, Immunological Response, Bay Scallop, Algicide, Algal Toxin, Palmitoleic Acid, Okadaic Acid Student number: 2014-31493