Buoyancy adaptations in a swim‐bladderless Antarctic fish

Joseph T. Eastman, Arthur L. DeVries

Research output: Contribution to journalArticlepeer-review


The endemic Antarctic teleosts of the suborder Notothenioidei are bottom dwellers. They lack swim bladders, are heavier than seawater, and feed on or near the bottom. The midwaters surrounding the Antarctic continent are productive and underutilized by fishes. There is an evolutionary trend toward pelagism in some notothenioids. We discovered that the largest Antarctic fish, Dissostichus mawsoni, was neutrally buoyant. Attainment of neutral buoyancy was associated with specializations of the skeletal, integumentary, muscular, and digestive systems. The skeleton had a low mineral content and contained considerable cartilage. Scales were also incompletely mineralized. Static lift was obtained from extensive lipid (mostly triglyceride) deposits. A 2–8 mm subcutaneous lipid layer accounted for 4.7% of the body weight. White muscle also contained much lipid–23% on a dry weight basis, or 4.8% of the body weight. Microscopic examination suggested that the liver was active in lipid metabolism, although it was not an organ of buoyancy. Stellate (perisinusoidal) cells with many lipid droplets were a very prominent cytological component of the liver. These specializations made Dissostichus neutrally buoyant and capable of inhabiting the food‐rich Antarctic midwaters.

Original languageEnglish (US)
Pages (from-to)91-102
Number of pages12
JournalJournal of Morphology
Issue number1
StatePublished - Jan 1981

ASJC Scopus subject areas

  • Animal Science and Zoology
  • Developmental Biology


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