Expression of Hsp70, Na/K ATP-ase, HIF-1α, IL-1β and TNF-α in captive Pacific bluefin tuna (Thunnus orientalis) after chronic warm and cold exposure

+ /K + ATP-ase, HIF-1α, IL-1β and TNF-α in captive Pacific bluefin tuna (Thunnus orientalis) after chronic warm and cold exposure a b s t r a c t a r t i c l e i n f o Keywords: Bluefin tuna Gene expression HIF-1α Hsp70 IL-1β Na + /K + ATP-ase TNF-α temperature Bluefin tuna (Thunnus spp.) are recently evolved teleosts with exceptional physiological and morphological specializations, whose aquaculture has become an increasing sector of the bluefin fishery. We studied the molecular expression of target gene transcripts in respect to experimental chronic cold and warm exposure in Pacific bluefin tuna liver, spleen, kidney and gill. The genes of interest were chosen as representative " biomarkers " , shown to change in fish exposed to temperature challenges: chaperon molecules (Hsp70); proteins engaged in active transport (Na + /K + ATP-ase); oxygen-dependent genes (HIF-1α); and cytokines (IL-1β, TNF-α). In captive Pacific bluefin tuna, these genes showed constitutive expression in all organs examined. A seven-week chronic exposure to cold temperature resulted in shifts in expression levels of oxygen-dependent HIF transcripts in spleen and gill, and Hsp70 in spleen, while other gene transcripts remain unaffected. The results indicate that a long-term exposure to cold imposes physiological pressure on this endothermic fish species, especially on haemaotopoietic and gas-exchange organs. We suggest that these two genes can be considered as potential biomarkers for thermal shifts in captive bluefin. Tunas represent the most valuable fisheries and finfish aquaculture product currently recognized, with more than a half of the total world production concentrated in the Mediterranean Sea. Ranching operations also extend globally to many regions including North America and Australia (Miyake et al., 2003; Fromentin and Powers, 2005). However, wild bluefin tuna fisheries have reached a plateau and efforts to ranch tunas and complete the aquaculture cycle have rapidly expanded. The expansion of bluefin tuna production through aquaculture largely depends upon our ability to maintain captive populations of bluefin tunas for rearing, reproduction and fingerling grow out. To improve the capacity to keep bluefin, reduction of the health risks and environmental influences will have to be defined. Molecular tools for characterizing the captive population health status and its physiology as the response to abiotic factors must be established in the captive environment, bur prior to that we need to detect and quantify appropriate parameters, indicative of fish response. Gene expression as an indicator of fish health …