Modulated Expression and Activities of Ruditapes philippinarum Enzymes After Oxidative Stress Induced by Aerial Exposure and Reimmersion.

Hongtao Nie,Xiwu Yan,Dongdong Li,Zihan Zhou,Baiying Guo,Kunyin Jiang

doi:10.3389/fphys.2020.00500

Abstract

Ruditapes philippinarum, is an economically and scientifically important bivalve mollusk. Its tolerance of aerial exposure has long been considered an important trait for its survival under acute environmental stress. In this study, the effects of air exposure at high and low temperatures (28 and 4°C) on the survival, antioxidant and metabolic enzyme activities, and the expression of antioxidant and immune-related genes in R. philippinarum were investigated. The activities of antioxidant and metabolic enzymes [superoxide dismutase (SOD), α-amylase, and proline hydroxylase (PHD)] were significantly affected by aerial exposure and reimmersion (reoxygenation) at both low (4°C) and high (28°C) temperatures. Moreover, the mRNA expression of α-amylase, SOD, and C-type lectin was also examined, which reveals these genes were significantly affected by aerial exposure challenge. In addition, the effects of aerial exposure and reimmersion on survival rate were calculated to evaluate the recovery capacity of Manila clam after aerial exposure at high and low temperatures. All individuals survived under low temperature aerial exposure for 24 h and reimmersion for 120 h. However, individuals died after reimmersion for 12 h following high temperature aerial exposure, and mortality peak occurred at 48 h. These data indicate that long-term aerial exposure during the transportation of clams should be in a low temperature environment. This study demonstrates that enzyme expression and activities linked to the stress response increase during the aerial exposure of R. philippinarum and provide useful information for future work on the molecular basis of tolerance of aerial exposure stress.

Highlights

The Manila clam, Ruditapes philippinarum, is an economically and scientifically important marine bivalve species with a wide geographic distribution, extending from Europe to Asia (Zhang and Yan, 2006, 2010)
The changes in physiological indices during the process of resistance to air exposure were investigated by monitoring the changes in the metabolic and antioxidant enzyme activities of R. philippinarum under the stress imposed by aerial exposure and reimmersion in water at different temperatures
This study provides new insights into the physiological and biochemical mechanisms underlying aerial exposure tolerance in R. philippinarum and extends our understanding of the physiological changes that occur in response to low oxygen availability, the fundamental adaptive physiology of this organism, and the molecular mechanisms operating during aerial exposure

Summary

Introduction

The Manila clam, Ruditapes philippinarum, is an economically and scientifically important marine bivalve species with a wide geographic distribution, extending from Europe to Asia (Zhang and Yan, 2006, 2010). Its ability to cope with abiotic and biotic stresses is vital to its survival because it has an Response of Clam to Aerial Exposure intertidal benthic lifestyle, and is subjected to cycles of emersion and reimmersion during the tidal cycle. Emersion times are longest for animals in the high intertidal zone, so these individuals are often subjected to aerial exposure. Many aquatic species, such as shellfish, can experience aerial exposure during their harvest and transportation. Little is known about the mechanisms underlying the regulation of the physiological and immune responses to aerial exposure in the Manila clam (Yin et al, 2017)

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