Study
Vertebrates without erythrocytes and blood pigment
Ruud, Johan T.
Nature, 1954
Examined the blood of Antarctic icefish, which had been reported by whalers to be colourless, and measured its oxygen-carrying capacity and cell content.
- Studied in
- Channichthyidae
- Sample size
- specimens examined from Antarctic waters
These fish have essentially no red blood cells and no haemoglobin. Their blood carries oxygen only in physical solution, at roughly a tenth of the capacity of ordinary fish blood.
What it means
The authors' reading, and ours. Where they differ, that difference is the point.
How the authors put it
A vertebrate can live without haemoglobin, in cold well-oxygenated water, with compensating changes to heart and circulation.
How NatureHQ reads it
A genuinely astonishing result and one NatureHQ is careful with. The icefish is not a better-designed animal; the current reading is that it lost something and compensated, which is a different and more interesting story than an adaptation to the cold.
- A short observational report; the physiological compensations were characterised much later.
What this study is used for on NatureHQ
One study can inform several subjects. Here is everywhere this one is cited.
Icefish
Antarctic icefish have no haemoglobin and colourless blood. The evidence points to a loss they got away with in cold, oxygen-rich water — not an improvement, and not an adaptation to the cold.
Icefish
No advantage to lacking haemoglobin has ever been demonstrated in icefish. The suggestion that thinner blood is easier to pump in the cold is a hypothesis, and the compensations the fish maintain are expensive.
Published by: Nature PortfolioPublished in a Nature Portfolio journal.
Checked against Crossref on 2026-09-28, and they agree on the title, the authors and the year.
NatureHQ summarises research in its own words and does not reproduce published text. Reviewed 2026-09-03.