Metabolic Demand, Oxygen Supply, and Critical Temperatures in the Antarctic BivalveLaternula elliptica

Abstract

Oxygen consumption ( ), heartbeat rate and form, and cirMo 2 culating hemolymph oxygen content were measured in relation to temperature in the large Antarctic infaunal bivalve Laternula elliptica. After elevations in temperature from 0Њ to 3Њ, 6Њ, and then 9ЊC, and heartbeat rate rose to new levels, whereaṡ Mo 2 maximum circulating hemolymph oxygen content fell. At 0ЊC, was 19.6 mmol O 2 h Ϫ1 for a standard animal of 2-g tissuė Mo 2 ash-free dry mass, which equates to a 8.95-g tissue dry-mass or 58.4-g tissue wet-mass animal. Elevation of metabolism following temperature change had acute Q 10 values between 4.1 and 5, whereas acclimated figures declined from 3.4 (between 0Њ and 3ЊC) to 2.2 (3Њ-6ЊC) and 1.9 (6Њ-9ЊC). Heartbeat rate showed no acclimation following temperature elevations, with Q 10 values of 3.9, 3.2, and 4.3, respectively. Circulating hemolymph oxygen content declined from 0Њ to 3Њ and 6ЊC but stayed at a constant Po 2 (73-78 mmHg) and constant proportion (∼50%) of the oxygen content of the ambient water. At 9ЊC, and heartbeat rate both peaked at values 3.3 times thosė Mo 2 measured at 0ЊC, which may indicate aerobic scope in this species. After these peaks, both measures declined rapidly over the ensuing 5 d to the lowest measured in the study, and the bivalves began to die. Hemolymph oxygen content fell dramatically at 9ЊC to values between 2% and 12% of ambient water O 2 content and had a maximum Po 2 of around 20 mmHg. These data indicate an experimental upper lethal temperature of 9ЊC and a critical temperature, where a long-term switch to

Plasticity in shell morphology and growth among deep-sea protobranch bivalves of the genus Yoldiella (Yoldiidae) from contrasting Southern Ocean regions

“…These turbulent and complex oceanographic processes increase heterogeneity in a system that may otherwise be considered highly stenothermal and stable (Barnes et al, 2006;Clarke et al, 2009). Small changes in temperature are known to cause drastic changes in metabolic rates of Antarctic benthic invertebrates in shallow water (Peck et al, 2002;Peck et al, 2004) but to date there is no published work on metabolic rates of deep-sea Antarctic invertebrates.…”

Oxygen limited thermal tolerance in fish?

“…Early evidence collected in marine invertebrates (annelids and sipunculids) demonstrated a transition to anaerobic metabolism (including mitochondrial anaerobiosis) at both cold and warm temperature extremes (Zielinski and Pörtner, 1996;Sommer et al, 1997), later on confirmed in crustaceans (Frederich and Pörtner, 2000) and molluscs, i.e. bivalves, gastropods and cephalopods (Pörtner and Zielinski, 1998;Pörtner et al, 1999;Peck et al, 2002;Sokolova and Pörtner, 2003). Studies in a sipunculid (Sipunculus nudus, Zielinski and Pörtner, 1996) and the spider crab (Maja squinado, Frederich and Pörtner, 2000) investigated the pattern of coelomic fluid/haemolymph oxygen tensions in relation to warming and/or cooling and demonstrated development of hypoxia which preceded the onset of anaerobic metabolism towards both cold and warm temperature extremes.…”

“…Inclusion of Antarctic marine invertebrates in this picture revealed very narrow windows of thermal tolerance in these organisms, in a temperature range just above freezing. An early transition to "heat" induced anaerobiosis between 2 and 6 • C seen in bivalves reflected the permanently low temperatures of Antarctic seas Peck et al, 2002).…”

Production of reactive oxygen species by isolated mitochondria of the Antarctic bivalve Laternula elliptica (King and Broderip) under heat stress

“…Portner,2 001), however, display a pejus temperature at 4 8C, beyond which a decreased level of aerobic scope limits ecological performance (activity and reproduction) and hence survival of the animals. Aerobic scope is lost and transition to anaerobic metabolism occurs between 6 and 9 8C (Peck et al, 2002). According to Portner (2001), pejus temperatures are more indicative of the limits of geographical distribution of a species, than the temperature extreme an organism can tolerate passively for some time until it dies.…”