Scientists from the UK have identified the first fish species known to undergo hibernation during the winter.
Publishing their results in the journal PLoS One, Hamish Campbell, Keiron Fraser, Charles Bishop, Lloyd Peck and Stuart Egginton studied the physiology of the Antarctic fish Notothenia coriiceps, and found it to suppress metabolic activity irrespective of water temperature during winter months.
While many mammals, birds, reptiles and amphibians are capable of hibernating over winter, fishes were thought to be incapable of doing so because the reduction in metabolic rate in fishes is directly proportional to the decrease in water temperature and they appear to be incapable of further suppressing their metabolic rate independently of temperature.
Video: British Antarctic Survey
The authors monitored the growth and physiology of N. coriiceps in an inshore area off Rothera Research Station (British Antarctic Survey), Adelaide Island, Antarctica; growth rate was measured over a single winter, while swimming activity, heart rate and metabolism were recorded by miniature electronic devices over a full annual cycle.
They found that N. coriiceps in their study exhibited a significant winter decrease in activity, heart rate, metabolism and growth (the fish that could not normally be handled in the summer months were sluggish and unresponsive when caught by SCUBA divers during the winter).
This decrease is not due to temperature (as is the case for other fishes), because the Antarctic marine environment is thermally stable the whole year round. It is thought that light (photoperiod) is an environmental cue that causes the fish to hibernate.
Fish have an overt sensitivity to light and the seasonal extremes of photoperiod at high latitudes in the absence of thermal change make it an obvious environmental cue for N. coriiceps.
The study demonstrates that at least some fish species can enter a dormant state similar to hibernation that is not temperature driven and presumably provides seasonal energetic benefits.
For more information, see the paper: Campbell, HA, KPP Fraser, CM Bishop, LS Peck and S Egginton (2008) Hibernation in an Antarctic fish: on ice for winter. PLoS ONE 3, e1743. doi:10.1371/journal.pone.0001743