The Influence Of Blood Gas Properties On Gas Tensions And Ph Of Ventral And Dorsal Aortic Blood In Free-SwimmingTuna, Euthynnus Affinis

Abstract

We have developed a technique for capture, anaesthetization, instrumentation and release of tuna and have made the first determinations of blood gas values in dorsal and ventral aortae of free-swimming tuna. Dorsal aortic Po2 varied from 34.5 to 91.7 mmHg, and Pcoco2 ranged from 3.7 to 7mmHg. Dorsal aortic blood [pHa = 7.77 ± 0.04 (8), mean ± one S.E.M. (N)] was more alkaline than ventral aortic blood [pHv = 7.65 ± 0.02 (7)]. Warming dorsal aortic blood from 25 to 35 °C in a closed system caused Po2 and PCOCO2 to rise and pH to fall. Oxygen-combining curves forwhole blood were sigmoid [mean Hill's number = 1.72 ± 0.05 (11), range 1.57-2.0]and P50 over the pH range found in free-swimming animals was 21 ± 1.75(8) mmHg. The CO2-induced Bohr coefficient (ΔlogP50/Δ pH) was −0.59 ± 0.046(30). Unusual features of CO2-combining curves are attributed to a significant Rooteffect. Although these in vitro properties of tuna whole blood are at variance withother published data on tuna they nevertheless substantiate our determinations madein vivo.

Temperature independence of haemoglobin–oxygen affinity in smalleye Pacific opah (Lampris incognitus) and swordfish (Xiphias gladius)

“…This is not the case as closedsystem warming greatly increased the P O2 of swordfish blood (Fig. 6B), and similar results have been reported for bigeye tuna (Thunnus obesus) and kawakawa (Euthynnus affinis) (Jones et al, 1986;Lowe et al, 2000). It seems unlikely that O 2 would be lost from the arterial vessels upstream of the capillaries, especially given the arterioles and venules of vertebrate heat-exchanging retia, as well as the diffusion distance between them, are about an order of magnitude greater than the vessels of a rete specialized for gas exchange, the swim bladder rete (Carey et al, 1985;Clark et al, 2008;Graham and Dickson, 2001;Lemons et al, 1987;Stevens et al, 1974).…”