Crab CRISIS!

There are species around us that are silently disappearing, and we are not even aware that they exist! The Horseshoe crab, a survivor from ages past, is one such species. What can we do?

- PRIYANJANA PRAMANIK

Horseshoe crabs have often been called ‘living fossils’, with their evolutionary history dating back to half a billion years ago, and the four living species looking extremely similar to the fossilised remains of their ancestors. Around the world, horseshoe crabs are disappearing, either because of the loss of their habitats and breeding grounds, or due to overharvesting. I was lucky enough to encounter some of these fascinating animals in the Indian Sundarbans.

About 480 million years ago, the world was a very different place. Oceans covered everything north of the tropics, while the bulk of the world’s land, including southern Europe, Africa, South America, Antarctica and Australia, was concentrated into a supercontinent called Gondwana. Plants did not have leaves, and the first air-breathing fish were starting to evolve into amphibians. Life existed, sure, but we would not have recognized most of this alien planet.

The oceans, much shallower than today, were filled with a dizzying variety of life, from ancient fish species to cephalopods (like squid and octopus) and trilobites. Also among them were horseshoe crabs of the family Limulidae – arthropods, just like today’s scorpions and spiders. While horseshoe crabs may look like crabs, they are not related to them at all.

Most of these ancient life forms disappeared 250 million years ago, when nine-tenths of life and 95% of marine plants and animals were killed off. Scientists are not sure of exactly what caused this mass extinction, but perhaps it was the volcanic eruptions in modern-day Siberia, which released huge amounts of greenhouse gases in the air, making global temperatures soar, and acidifying the oceans.