22/09/2025
✨ Did you know this giant snail helps save coral reefs? 🐌🌊
Meet the horned helmet (Cassis cornuta). It’s the largest of the helmet shells and can grow up to 35 cm.
🔹 Reproduction
Females lay enormous egg masses, often upside down under overhangs. Each mass holds thousands of eggs, which hatch into planktonic larvae before settling on the reef. That’s what you see in this photo and in our area, they also lay near wrecks and other rocky outcrops.
🔹 Diet
Slow-moving but powerful, the horned helmet preys on sea urchins and starfish, including the venomous crown-of-thorns starfish. By doing so, it helps protect reefs from one of their biggest natural threats.
🔹 Mauritius Connection
Found right here on our reefs, this gastropod plays a vital role in keeping coral ecosystems healthy by eating the crown-of-thorns, as this population can get out of control at times. The helmet snail is also valued for its shell so it’s an instance of humans having a large impact on the health of the reef as the crown-of-thorns eats 6-13 square meters of coral tissue per year but when there is an outbreak, they each consume even more and at a significantly faster rate. This is why this snail is protected in Queensland as the Great Barrier Reef has had its fair share of crown-of-thorns outbreaks over the years. Even the slowest creatures can make a big impact 💙.
👉 What unusual marine life has surprised you on a dive? Share below! 👇
