Will jumping snails prevail? Influence of near-future CO2, temperature and hypoxia on respiratory performance in the tropical conchGibberulus gibberulus gibbosus

Abstract

Tropical coral reef organisms are predicted to be especially sensitive to ocean warming because many already live close to their upper thermal limit, and the expected rise in ocean CO 2 is proposed to further reduce thermal tolerance. Little, however, is known about the thermal sensitivity of a diverse and abundant group of reef animals, the gastropods. The humpbacked conch (Gibberulus gibberulus gibbosus), inhabiting subtidal zones of the Great Barrier Reef, was chosen as a model because vigorous jumping, causing increased oxygen uptake (Ṁ O2 ), can be induced by exposure to odour from a predatory cone snail (Conus marmoreus). We investigated the effect of present-day ambient (417-454 µatm) and projected-future (955-987 µatm) P CO2 on resting (Ṁ O2,rest ) and maximum (Ṁ O2,max ) Ṁ O2 , as well as Ṁ O2 during hypoxia and critical oxygen tension (P O2,crit ), in snails kept at present-day ambient (28°C) or projectedfuture temperature (33°C). Ṁ O2,rest and Ṁ O2,max were measured both at the acclimation temperature and during an acute 5°C increase. Jumping caused a 4-to 6-fold increase in Ṁ O2 , and Ṁ O2,max increased with temperature so that absolute aerobic scope was maintained even at 38°C, although factorial scope was reduced. The humpbacked conch has a high hypoxia tolerance with a P O2,crit of 2.5 kPa at 28°C and 3.5 kPa at 33°C. There was no effect of elevated CO 2 on respiratory performance at any temperature. Long-term temperature records and our field measurements suggest that habitat temperature rarely exceeds 32.6°C during the summer, indicating that these snails have aerobic capacity in excess of current and future needs.

Near-future ocean warming and acidification alter foraging behaviour, locomotion, and metabolic rate in a keystone marine mollusc

“…Elevated pCO 2 , according to OA scenarios for the year 2100 and beyond, had no significant impact on metabolic rate of S. striatus at ambient temperature (28 °C). Similar results were found for another mollusc, the tropical humpbacked conch (Gibberulus gibberulus gibbosus) 58 , where there was no effect of elevated pCO 2 on respiratory performance at any of the tested temperatures (range 28-33 °C) (also see ref. 11 ).…”

Are global warming and ocean acidification conspiring against marine ectotherms? A meta-analysis of the respiratory effects of elevated temperature, high CO2and their interaction

“…This is also supported by the data, as several of the acutely performed measurements of AAS reveal a typical bell-shaped increase–optimum–decrease-type response [robust shell ( Littoraria undulata ; Patnaik et al. , 1985 ); bald notothen ( Lowe and Davison, 2006 ); sockeye salmon ( Oncorhynchus nerka ; Eliason et al , 2011 ); shorthorn sculpin ( Myoxocephalus scorpius ), Arctic sculpin ( Myoxocephalus scorpioides ) and Arctic staghorn sculpin ( Gymnocanthus tricuspis ; Seth et al ., 2013 ); goldfish ( Carassius auratus ; Ferreira et al ., 2014 ); rainbow trout ( Oncorhynchus mykiss ; Chen et al ., 2015 ); European crayfish ( Astacus astacus ) and giant tiger prawn ( Penaeus monodon ; Ern et al , 2015 ); humpback conch ( Gibberulus gibberulus gibbosus ; Lefevre et al , 2015 ); and bonefish ( Albula vulpes ; Nowell et al ., 2015 )]. Intriguingly, a study on a high-Arctic population of blue mussel ( Mytilus edulis ) acclimated to 1°C ( Thyrring et al , 2015 ) found that AAS during an acute temperature challenge was highest at 7°C, even though this population probably never experiences a temperature higher than 5°C during the warmest month of the year.…”

“…The variability detected in the response in to elevated CO 2 is also reflected in AAS, which decreases in some studies [jumbo squid ( Rosa and Seibel, 2008 ); yellowstriped and fourline cardinalfish ( Munday et al ., 2009 ); and Shiba shrimp ( Dissanayake and Ishimatsu, 2011 )], but not in others [ambon damsel ( Pomacentrus amboinensis ), lemon damsel, brown dottyback ( Pseudochromis fuscus ; Couturier et al ., 2013 ); European sea bass ( Pope et al . 2014 ); red drum ( Esbaugh et al ., 2016 ); small-spotted catshark ( Green and Jutfelt, 2014 ); and humpbacked conch ( Lefevre et al ., 2015 )], and in fact, even increases in a third, albeit small, group [spiny chromis damselfish ( Rummer et al ., 2013 ); and Atlantic halibut ( Gräns et al ., 2014 )]. Overall, these outcomes were not influenced by methodology, because the proportion of studies finding an effect vs. no effect, and an increase vs. a decrease, was the same for studies measuring during exercise or after chasing.…”

“…to avoid unfounded speculation, some studies reflect little or only vaguely upon the mechanistic cause for the observed response, whether it was a reduction (e.g. Rosa and Seibel, 2008 ; Dissanayake and Ishimatsu, 2011 ; Tirsgaard et al , 2015b ) or no change ( Schalkhausser et al , 2013 ; Lefevre et al , 2015 ). Given the hypothesis that CO 2 acts as a limiting factor, it is counterintuitive to find that increases in some animals exposed to elevated CO 2 .…”

Physiological Challenges to Fishes in a Warmer and Acidified Future

“…Moreover, since GABA A receptors also occur in the nervous system of many aquatic invertebrates, the problem may not stop at fish. Studies on a tropical marine gastropod, the humpbacked conch (Gibberulus Gibberulus gibbosus), have indicated that, although these snails can readily tolerate projected rises in water temperature (42), they too display behavioral changes when exposed to 1,000 atm of CO 2 (66). By contrast, air-breathing animals (including humans), would most likely not have to worry about altered GABA A receptor function.…”