Synthesis and recycling of antifreeze glycoproteins in polar fishes

Clive W. Evans, Linn Hellman, Martin Middleditch, Joanna M. Wojnar, Margaret A. Brimble, Arthur L. Devries

Research output: Contribution to journalArticle

Abstract

Evolutionary disparate Antarctic notothenioids and Arctic gadids have adapted to their freezing environments through the elaboration of essentially identical antifreeze glycoproteins (AFGPs). Here we show that this convergence of molecular identity, which evolved from unrelated parent genes, extends to convergence in physiological deployment. Both fish groups synthesize AFGPs in the exocrine pancreas from where they are discharged into the gut to inhibit the growth of ingested ice. Antifreeze glycoproteins not lost with the faeces are resorbed from the gut via the rectal epithelium, transported to the blood and ultimately secreted into the bile, from where they re-enter the gastrointestinal tract. Antifreeze glycoprotein recirculation conserves energy expenditure and explains how high levels of AFGPs reach the blood in notothenioids since, unlike Arctic gadids which also synthesize AFGP in the liver, AFGP secretion in notothenioids is directed exclusively towards the gastrointestinal lumen. Since AFGPs function by inhibiting ice crystal growth, ice must be present for them to function. The two fish groups are thus faced with an identical problem of how to deal with internal ice. Here we show that both accumulate AFGPs within ellipsoidal macrophages of the spleen, presumably adsorbed to phagocytosed ice crystals which are then held until a warming event ensues.

Original languageEnglish (US)
Pages (from-to)259-268
Number of pages10
JournalAntarctic Science
Volume24
Issue number3
DOIs
StatePublished - Jun 1 2012

Keywords

  • AFGP
  • Arctic gadids
  • freeze-avoidance
  • notothenioid
  • polar cod

ASJC Scopus subject areas

  • Oceanography
  • Ecology, Evolution, Behavior and Systematics
  • Geology

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  • Cite this

    Evans, C. W., Hellman, L., Middleditch, M., Wojnar, J. M., Brimble, M. A., & Devries, A. L. (2012). Synthesis and recycling of antifreeze glycoproteins in polar fishes. Antarctic Science, 24(3), 259-268. https://doi.org/10.1017/S0954102012000119