Octopuses Have Three Hearts and Blue Blood
Octopuses are among the most alien creatures on Earth — with three hearts, blue copper-based blood, and the ability to edit their own RNA.
A quick, easy-to-understand overview
Three Hearts!
Octopuses have three hearts:
- Two branchial hearts pump blood through the gills
- One systemic heart pumps blood through the rest of the body
Fun fact: the systemic heart actually stops beating when the octopus swims!
Blue Blood
Instead of iron-based hemoglobin, octopuses use copper-based hemocyanin. This makes their blood blue!
Super Smart
Octopuses can open jars from the inside, use tools, recognize individual human faces, and escape from almost any container.
A deeper dive with more detail
The Alien Intelligence of Octopuses
Octopuses offer insights into alternative evolutionary paths to intelligence.
Circulatory System
The three-heart system evolved to compensate for hemocyanin's inefficiency as an oxygen carrier.
| Property | Hemocyanin | Hemoglobin |
|---|---|---|
| Metal | Copper | Iron |
| Color | Blue | Red |
| Cold water efficiency | Better | Worse |
Distributed Nervous System
The octopus has ~500 million neurons. Two-thirds are in the arms, not the brain. Each arm can react independently.
RNA Editing
Coleoid cephalopods extensively edit their mRNA, allowing rapid adaptation of neural proteins without permanent DNA changes.
Key Points
- Octopuses diverged from our lineage ~750 million years ago
- They represent completely independent evolution of complex intelligence
- Their short lifespan (1-5 years) limits cultural transmission
Full technical depth and nuance
Cephalopod Biology: Convergent Intelligence
Octopus hemocyanin (OcHc) is a massive multi-subunit metalloprotein (~3.5 MDa) with cooperative oxygen binding (Hill coefficient n ≈ 2-4).
The neural architecture features ~500 million neurons organized fundamentally differently from vertebrates, with each arm containing ~40M neurons in semi-autonomous ganglia.
Adar enzymes convert adenosine to inosine at ~60% of coding transcripts in the nervous system, representing a trade-off between DNA-level evolution and transcriptomic plasticity.
Key Points
- Extensive RNA editing challenges the central dogma's simplicity
- The distributed cognition has inspired decentralized robotics architectures
- Cephalopod skin contains opsins, suggesting distributed visual processing
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