Juveniles Are More Resistant to Warming than Adults in 4 Species of Antarctic Marine Invertebrates

Abstract

Juvenile stages are often thought to be less resistant to thermal challenges than adults, yet few studies make direct comparisons using the same methods between different life history stages. We tested the resilience of juvenile stages compared to adults in 4 species of Antarctic marine invertebrate over 3 different rates of experimental warming. The species used represent 3 phyla and 4 classes, and were the soft-shelled clam Laternula elliptica, the sea cucumber Cucumaria georgiana, the sea urchin Sterechinus neumayeri, and the seastar Odontaster validus. All four species are widely distributed, locally abundant to very abundant and are amongst the most important in the ecosystem for their roles. At the slowest rate of warming used (1°C 3 days−1) juveniles survived to higher temperatures than adults in all species studied. At the intermediate rate (1°C day−1) juveniles performed better in 3 of the 4 species, with no difference in the 4th, and at the fastest rate of warming (1°C h−1) L. elliptica adults survived to higher temperatures than juveniles, but in C. georgiana juveniles survived to higher temperatures than adults and there were no differences in the other species. Oxygen limitation may explain the better performance of juveniles at the slower rates of warming, whereas the loss of difference between juveniles and adults at the fastest rate of warming suggests another mechanism sets the temperature limit here.

Elevated temperature causes metabolic trade-offs at the whole organism level in the Antarctic fish Trematomus bernacchii

“…This agrees well with low acclimation capacities reported for Antarctic marine ectotherms and acclimation times of 21-36 days reported for other Antarctic fish species (Peck et al, 2014).…”

“…Usually, the earliest life stages are more temperature sensitive, while juveniles and growing adults can exploit the largest range in thermal habitats. In reproductively mature adults, thermal tolerance decreases again, as oxygen has to be supplied to eggs and sperm, lowering thermal capacity (Pörtner and Farrell, 2008;Pörtner and Peck, 2010;Peck et al, 2013). Because of the size and maturation stages of T. bernacchii used in this experiment, animals can be considered to be juveniles.…”

Age-related thermal response: the cellular resilience of juveniles

“…Given the expression profiles for the older animals at 3°C, it is almost as if the older animals are shutting down their metabolism in response to a challenge rather than producing an active cellular response. In other experiments, younger animals also have a better respiratory response to sedimentation, they rebury faster and survive better after an injury, with an enhanced immune response and survive to higher upper lethal temperatures Husmann et al 2011;Peck et al 2013). Hence, the expression data described here support not only the physiological results but also those of previous expression studies in which the younger animals were shown to display a more rapid and active cellular response to stress (Husmann et al 2014;Clark et al 2013).…”

“…However, analysis of the expression profiles using age as the variable factor did show significant differences between young and old animals. These data emphasised the importance of age underlying environmental stress responses, as identified in previous experiments involving the environmental challenges of sediment deposition, iceberg scour, physical injury, microbial infection, hypoxia and heat Husmann et al 2011Husmann et al , 2014Clark et al 2013;Peck et al 2013). Mitochondrial respiratory chain …”

Shore-level size gradients and thermal refuge use in the predatory sea star Pisaster ochraceus: the role of environmental stressors

“…Third, we conducted laboratory experiments to determine whether differences in thermo-and desiccation-tolerance between size classes can explain the observed pattern. According to the oxygen-limitation hypothesis (Pörtner 2002(Pörtner , 2006, and supporting evidence (Peck et al 2009(Peck et al , 2013, we hypothesized that smaller individuals can withstand higher temperatures than larger ones because they have a proportionately larger re spiratory surface area relative to volume of tissue.…”