Metabolic and behavioural adaptations during early development of the Antarctic silverfish, Pleuragramma antarcticum
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The Antarctic silverfish Pleuragramma antarcticum is a keystone species in the Ross Sea ecosystem, providing one of the major links between lower and higher trophic levels. Despite the importance of this species, surprisingly little is known of its early development and behaviour. Here, we determine the metabolic capacity of Pleuragramma embryonated eggs and larvae and make comparisons with developing stages of another notothenioid, the naked dragonfish Gymnodraco acuticeps. We also show that although large numbers of embryonated eggs of Pleuragramma are found floating among the platelet ice of Terra Nova Bay, they are able to sink prior to hatching in late spring, likely reducing the risk of exposure to the potentially lethal, ice-laden surface environment. Applying Stoke’s law, we determine the change in density required for embryonated eggs to sink at the measured rate and then consider possible mechanisms by which this might occur. Significantly, newly hatched larvae are positively gravitactic and negatively phototactic, such that their swimming behaviour also directs them away from the risk of freezing in the icy surface waters. Measurement of the acute thermal tolerance shows that Pleuragramma larvae have, on average, a sustainable swimming performance breadth of about 17°C, which is significantly greater than that of other adult notothenioids. Although it lacks significant antifreeze capacity in its early developmental stages, Pleuragramma has other attributes that may ensure survival over a wider range of environmental temperatures than other more stenothermal Antarctic notothenioids. How it might adapt to prolonged environmental change arising from phenomena such as global warming, however, requires further investigation.
KeywordsPleuragramma Developmental descent Metabolism Behaviour Phototaxis Gravitaxis Thermal tolerance Ross Sea ecosystem
This work was supported by the National Science Foundation, Office of Polar Programs (#02-31006) and the Human Frontier Science Programme (RGP003/2009-C). The field activity at Stazione Mario Zucchelli was supported by the Italian Antarctic Project PNRA as part of the project ECOFISH (2004/8.04). We thank Paul Cziko, Eva Pisano and Lauren Fields for their input, our colleagues at Stazione Mario Zucchelli and Scott Base for their help and companionship in the field, and our referees (JT Eastman and DG Ainley) for their helpful comments.
Conflict of interest
The authors declare that they have no conflicts of interest.
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