Zoological Studies

Vol. 53, 2014

Short-term effects of thermal stress on the responses of branchial protein quality control and osmoregulation in a reef-associated fish, Chromis viridis

Cheng-Hao Tang1,2*, Ming-Yih Leu2,3, Katrina Shao4, Lie-Yueh Hwang5 and Wen-Been Chang2,3

1Institute of Marine Biotechnology, National Dong Hwa University, 2 Houwan Road, Checheng, Pingtung 944, Taiwan
2National Museum of Marine Biology and Aquarium, Pingtung 944, Taiwan
3Institute of Marine Biodiversity and Evolutionary Biology, National Dong Hwa University, Pingtung 944, Taiwan
4Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106-9610, USA
5Taishi Station, Mariculture Research Center, Fisheries Research Institute, Council of Agriculture, Taishi, Yulin 636, Taiwan

Background: Changes in ambient temperature seriously affect physiological regulation and biochemical reactions in ectotherms. However, transient elevation in oceanic temperature occurs naturally during the day. Short-term elevation in the ambient temperature affects different physiological responses in marine fish, including cellular protein stability and osmotic balance of the internal environment. Since fish gills are vital osmoregulatory organ which directly contacts external environment, activation of cytoprotective responses to maintain gill cell viability and biological function is essential for fish survival under challenging environmental conditions. The purpose of this study was to investigate the short-term effects of elevated temperature on physiological regulation in the gills of a marine teleost, blue green damselfish (Chromis viridis).
As part of the stress response, plasma glucose levels were induced by short-term hyperthermic exposure (12 h). Furthermore, upregulation of the levels of gill heat shock proteins (HSPs) and ubiquitinated proteins was essential for preventing the accumulation of protein aggregations in branchial cells of C. viridis under hyperthermic stress. The specific activity of branchial Na+/K+-ATPase (NKA), however, significantly reduced while the amount of protein was similar between normal and high-temperature groups.
Conclusions: The present study provided the evidence to illustrate that activation of the branchial protein quality control mechanism to carry out cytoprotective response was involved in coping with thermal stress. However, plasma osmolality and muscle water content, respectively, that slightly but evidently increased and decreased might result from impaired osmoregulatory ability due to hyperthermia-decreased gill NKA activity.

Key words: Thermal stress; Blue-green damselfish; Protein quality control; Osmoregulation.

*Correspondence: E-mail: ce: wtang@mail.ndhu.edu.tw