Stress responses to mild and acute temperature decrease for two strains of sea cucumber Apostichopus japonicus

Abstract

In order to understand the effect of low temperature shock to Apostichopus japonicus, we measured the concentration of soluble proteins, soluble sugars and five ions (Ca2+, Mg2+, Na+, Cl− and NO) derived from different organs to evaluate the adaptive capacities and stress responses to mild temperature decrease (MTD, initial temperature was set at 14°C and decreased from 8°C to −2°C by step changes of 2°C, temperature was decreased to each temperature through 24h) and to rapid temperature decrease (ATD, step changes of 2°C over 1.5h) in the laboratory. Two commercial strains of A. japonicus, hybrid Shuiyuan No. 1 sea cucumbers (Ss) and Dalian local sea cucumbers (Ls), were used as test animals. In the MTD treatments, concentrations of soluble proteins and soluble sugars on the whole showed similar trends of an initial increase, a subsequent decrease and then an increase to a level similar to or higher than the initial level. Ca2+ concentration increased to the maximum level at 4°C and did not return to the original concentration. The concentrations of Mg2+ and Cl− increased significantly to a higher level, which was maintained until the end of the experiment. However, the concentrations of Na+ and NO showed an opposite trend: an initial decrease in concentration to a low concentration that was maintained until the end of the experiment. In contrast, in the ATD experiment, the concentration of soluble proteins, soluble sugars, Mg2+, NO and Na+ showed a tendency for fluctuation or decrease. Only Ca2+ and Cl− concentrations showed a rising trend. Earlier responses and faster homeostatic ability were observed for Ss individuals than for Ls individuals, indicating a greater cold tolerance. Such findings provide the basis for improving aquaculture techniques for A. japonicus, particularly for providing a new stress-resistant sea cucumber variety for A. japonicus culture in farm ponds. Statement of relevanceThe manuscript titled “Stress responses to mild and acute temperature decrease for two strains of sea cucumber Apostichopus japonicus” was finished by Junhao Ning, Yaqing Chang, Wei Liu, Jian Song, Weijie Zhang and Jun Ding, we all made contribution to this manuscript and agreed with the authors' sorting order.This paper is first submitted in your journal. Neither the entire paper nor any part of its content has been published or has been accepted elsewhere. It is not being submitted to any other journal.We believe the paper may be of particular interest to the readers of your journal because the study reports that: (1) a preliminary relationship between the changes of soluble proteins, soluble sugars and five biogenic ions in A. japonicus and cold stress is established in the study; (2) the turning point of stress reaction in A. japonicus when suffering low-temperature was found at 0°C or at 2°C; and (3) we provide a new stress-resistant sea cucumber variety for A. japonicus culture in farm ponds.