25/05/2026
On May 21st, 2026, we were lucky enough to observe a pair of Tri-spine horseshoe crabs (Tachypleus tridentatus) mating on the beach of Pangatalan. A rare and precious sighting.
The smaller individual is the male: he attaches himself to the back of the female for several days during mating and egg-laying in the sand.
In Shark Fin Bay, horseshoe crabs are relatively common… but rarely seen. During the day, they stay buried in the mud at the bottom of the bay.
🌙 Nighttime is when you’re most likely to encounter them as they emerge to feed — except during mating season, when pairs come into shallow waters near the beach to spawn.
Despite its name, the horseshoe crab is not actually a crab, but a true “living fossil” with blue blood that helps save human lives every day.
This ancient arthropod — more closely related to spiders and scorpions than crustaceans — has roamed Earth’s oceans for over 450 million years, surviving dinosaurs and four mass extinctions with almost no change in appearance.
Its most fascinating secret flows through its veins: blue blood. Unlike humans, whose blood uses iron to transport oxygen, horseshoe crabs use copper. Even more incredible, their blood contains unique immune cells (amebocytes) that instantly react to bacterial toxins by forming a gel.
This extraordinary property is so valuable that an extract from their blood (the LAL test) is used worldwide to test the sterility of vaccines, implants and surgical equipment. If you’ve ever received an injection, you owe part of your safety to this incredible animal.
One last fun fact ✨
As they grow, horseshoe crabs must shed their shell. During their youth, they molt between 16 and 19 times before reaching adulthood. Once sexually mature (around 10 years old), they stop molting and can live up to 20 years.
A fascinating, discreet… and essential creature 💙
➡️ Follow us to continue exploring the incredible wildlife of Pangatalan together.
Blancpain
AFD - Agence Française de Développement
Embassy of France to the Philippines and Micronesia
Shark Fin Bay MPA Network
Palawan Council for Sustainable Development
WWF
Mission Blue
SMILO - Small Islands Organisation
Marine Conservation Institute
The Blue Quest
Cressi
DUNE WORLD