Ocean warming enhances malformations, premature hatching, metabolic suppression and oxidative stress in the early life stages of a keystone squid.
BACKGROUND
The knowledge about the capacity of organisms' early life stages to adapt to elevated temperatures is very limited but crucial to understand how marine biota will respond to global warming. Here we provide a comprehensive and integrated view of biological responses to future warming during the early ontogeny of a keystone invertebrate, the squid Loligo vulgaris.


RESULTS
Recently-spawned egg masses were collected and reared until hatching at present day and projected near future (+2°C) temperatures, to investigate the ability of early stages to undergo thermal acclimation, namely phenotypic altering of morphological, behavioural, biochemical and physiological features. Our findings showed that under the projected near-future warming, the abiotic conditions inside the eggs promoted metabolic suppression, which was followed by premature hatching. Concomitantly, the less developed newborns showed greater incidence of malformations. After hatching, the metabolic burst associated with the transition from an encapsulated embryo to a planktonic stage increased linearly with temperature. However, the greater exposure to environmental stress by the hatchlings seemed to be compensated by physiological mechanisms that reduce the negative effects on fitness. Heat shock proteins (HSP70/HSC70) and antioxidant enzymes activities constituted an integrated stress response to ocean warming in hatchlings (but not in embryos).


CONCLUSIONS
The stressful abiotic conditions inside eggs are expected to be aggravated under the projected near-future ocean warming, with deleterious effects on embryo survival and growth. Greater feeding challenges and the lower thermal tolerance limits of the hatchlings are strictly connected to high metabolic demands associated with the planktonic life strategy. Yet, we found some evidence that, in the future, the early stages might support higher energy demands by adjusting some cellular functional properties to increase their thermal tolerance windows.
Laboratório Marítimo da Guia, Centro de Oceanografia, Faculdade de Ciências da Universidade de Lisboa, Cascais, Portugal. rrosa@fc.ul.pt
Rui
R
Rosa
Marta S
MS
Pimentel
Joana
J
Boavida-Portugal
Tatiana
T
Teixeira
Katja
K
Trübenbach
Mário
M
Diniz
D000064:Acclimatization / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000378:metabolism; D001267:Atlantic Ocean; D002374:Catalase / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000196:embryology; D047108:Embryonic Development; D004734:Energy Metabolism / Q000502:physiology*; D005982:Glutathione Transferase / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism; D015227:Lipid Peroxidation; D049834:Loligo / Q000033:anatomy & histology* / Q000196:embryology* / Q000378:metabolism; D018384:Oxidative Stress / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology; D013482:Superoxide Dismutase / Q000378:metabolism; D015996:Survival Rate; D013696:Temperature
D006360:Heat-Shock Proteins; C005394:octopine; D001120:Arginine; D002374:Catalase; D013482:Superoxide Dismutase; D005982:Glutathione Transferase