This article was originally published on Sikho.ai. Read the full guide there.
Imagine a lizard that doesn't hunt insects or bask on sunny branches. Instead it plunges into cold ocean waters, dives nearly 100 feet deep, and scrapes algae off underwater rocks with razor-sharp teeth. This is the marine iguana — Earth's only ocean-foraging lizard.
In our full guide on Sikho.ai, we explore every adaptation. Here is the short version.
A One-of-a-Kind Evolutionary Story
Every other lizard species on Earth eats land-based food. The marine iguana, which lives only on the Galápagos Islands, evolved roughly 4.5 million years ago to exploit an untapped resource: the abundant algae growing in the cold Pacific waters around the islands.
Natural selection favored individuals with traits suited to ocean foraging. Over millions of years, this created the highly specialized marine reptile we see today.
Extreme Diving Abilities
Large males can dive 30 meters (98 feet) deep and stay underwater for up to one hour. Most spend just 5-10 minutes per dive. Their slow heartbeats and ability to tolerate cold water for extended periods are key adaptations.
The Salt-Sneeze
Marine iguanas eat salty algae. They get rid of the excess salt through specialized nasal glands that concentrate sodium chloride into a brine — which they expel by literally sneezing it out. This produces the characteristic white salt crusts you see on their faces.
Why They Matter
Marine iguanas are a textbook example of adaptive evolution and a flagship species for understanding how life evolves in extreme environments. They are also threatened — only ~22,000 remain in the wild.
Read the complete deep-dive on Sikho.ai's blog.
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