wiki.crvscience.com • 1395 Articles

Science Wiki

AI-assisted, human-supervised knowledge wiki spanning Earth & climate systems, genetics, molecular biophysics, vector entomology, and astrobiology.

← Wiki Index / /

🐙 Cell & Organismal Biology

Ocellated Icefish

The ocellated icefish (Chionodraco rastrospinosus) is an Antarctic fish with transparent, nearly colorless blood. Like all icefishes (Channichthyidae), it has no hemoglobin and no red blood cells, the only adult vertebrates known with this trait.

2 min read • Updated October 2026 • Knowledge Wiki • AI-Assisted & Human-Supervised

The ocellated icefish (Chionodraco rastrospinosus) is an Antarctic fish with transparent, nearly colorless blood. Like all icefishes (Channichthyidae), it has no hemoglobin and no red blood cells, the only adult vertebrates known with this trait.

Photo of Ocellated Icefish (Chionodraco rastrospinosus) — 📷 Photo: Valerie Loeb via Wikimedia Commons • Public domain

🧬 Field Guide Specimen: Open Ocellated Icefish in the CRV Science Field Guide to log the specimen, see its place among the Vertebrates lineages in the Cladogram Explorer, and test your recall in the Red List conservation game.

Blood Without Hemoglobin: How Can It Breathe?

Cold water holds much more dissolved oxygen, and icefish live in very cold, oxygen-rich seas near −1.9 °C. Their blood plasma carries a little oxygen directly. To compensate, they have large hearts, wide blood vessels, a large blood volume and a low metabolic rate. Oxygen also diffuses through their scaleless skin.

A Lost Gene Set

The hemoglobin genes were lost during the evolution of the group in the cold Southern Ocean. Whether the loss was an adaptation or a neutral accident is debated. Warming waters could put these fish at risk. See Climate change.

Antifreeze in the Family

Related Antarctic notothenioid fishes make antifreeze glycoproteins that prevent ice crystals from growing in their blood. Icefish share the same suborder.