The archaeogastropod molluscHaliotis iris: tissue and blood metabolites and allosteric regulation of haemocyanin function

Abstract

SUMMARY We investigated divalent cation and anaerobic end-product concentrations and the interactive effects of these substances and pH on haemocyanin oxygen-binding (Hc-O2) in the New Zealand abalone Haliotis iris. During 24 h of environmental hypoxia (emersion), d-lactate and tauropine accumulated in the foot and shell adductor muscles and in the haemolymph of the aorta, the pedal sinus and adductor muscle lacunae, whereas l-lactate was not detected. Intramuscular and haemolymph d-lactate concentrations were similar, but tauropine accumulated to much higher levels in muscle tissues. Repeated disturbance and short-term exposure to air over 3 h induced no accumulation of d- or l-lactate and no change in [Ca2+], [Mg2+], pH and O2-binding properties of the native haemolymph. The haemolymph showed a low Hc-O2 affinity, a large reverse Bohr effect and marked cooperativity. Dialysis increased Hc-O2 affinity, obliterated cooperativity and decreased the pH-sensitivity of O2 binding. Replacing Mg2+ and Ca2+ restored the native O2-binding properties and the reverse Bohr shift. l- and d-lactate exerted minor modulatory effects on O2-affinity. At in vivo concentrations of Mg2+ and Ca2+, the cooperativity is dependent largely on Mg2+, which modulates the O2 association equilibrium constants of both the high-affinity (KR) and the low-affinity (KT) states (increasing and decreasing, respectively). This allosteric mechanism contrasts with that encountered in other haemocyanins and haemoglobins. The functional properties of H. iris haemocyanin suggest that high rates of O2 delivery to the tissues are not a priority but are consistent with the provision of a large O2 reserve for facultatively anaerobic tissues during internal hypoxia associated with clamping to the substratum.

Short-Term Estivation and Hibernation Induce Changes in the Blood and Circulating Hemocytes of the Apple Snail Pomacea canaliculata

“…Hemocyanin concentration was estimated according to the method described by Behrens et al [ 30 ]. Fresh blood was diluted 30-fold in buffer (glycine 50 mM, EDTA 10 mM, pH 8.8), and absorbance was measured with a spectrophotometer at 346 nm.…”

Effects of acclimation temperature and exposure time on the scope for growth of the blackfoot Pāua (Haliotis iris)

“…Haemocyanin level was then determined from the absorbance at 346 nm using the Unicam 8625 UV/Vis spectrophotometer with a D2 lamp. Haemocyanin concentrations (Hcy) were calculated using a practical extinction coefficient determined from copper analysis (E mM Hcy, 1 cm = 22.84 for millimolar Hcy measured in a 1-cm cuvette) (Behrens et al 2002;Ragg and Taylor 2006):…”

“…In molluscs, haemocyanin transports oxygen and assists in immune responses (Jaenicke et al 2009). Elevating temperature can raise haemocyanin to transport more oxygen to the tissue, thus increasing haemolymph protein (Behrens et al 2002;Giomi and Pörtner 2013). Lu et al (2016) found that temperature affected both haemolymph sodium and potassium concentrations of the gazami crab (Portunus trituberculatus).…”