Neocalanus tonsus has a life cycle that includes a number of active growing stages and a long resting period. Neocalanus breeds in deep water at the end of winter. The eggs hatch into free-swimming larvae (nauplii) that bear little resemblance to adults. They feed, grow and start to make their way up to surface waters. They moult six times during their upward journey, developing into advanced larvae (copepodites) with elongated segmented bodies. They feed in surface waters during spring and summer, moulting another four times. At the end of summer the copepodites descend between 500 and 1,300 metres, where they enter a resting stage. They eat nothing for six or so months during autumn and winter. At the end of winter they moult a final time and emerge as adults, ready to breed.
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Source: J. M. Bradford-Grieve and others, ‘Potential contribution that the copepod Neocalanus tonsus makes to downward carbon flux in the Southern Ocean.’ Journal of Plankton Research 23, no. 9 (2001): 963–975.