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Spring is Here: Volunteers Help Horseshoe Crabs

Spring is Here: Volunteers Help Horseshoe Crabs

The horseshoe crab is a marvel by today’s standards. The creatures have been around hundreds of millions of years, making them living fossils and older than the dinosaurs.

There are many features of the horseshoe crab that makes it extraordinary – their eyes, their blood, their ability survive all this time – and yet, they’re in decline. So, what do we know about them and how can we help them?

First things first, horseshoe crabs are harmless to humans. They’re carnivores, but only like eating soft things like worms. They also have a claw at the tip of eight of their ten legs, as well as pincer-like arms, but these aren’t a threat to someone holding the crab.

The tail of the creature is long and rigid, and while it might look quite threatening, the main purpose of it is to help the crab flip over if its gets stuck on its back. The entire creature, besides its tail, is covered by a carapace or shell, and when the crab lies on the sea bed, it looks very much like a species of ray.

From above, the horseshoe crab looks more like a ray than a crustacean

Of the crab’s ten eyes, one pair is able to detect both visible and ultraviolet light. The eyes are located all over the body, including on its tail and its shell – the latter’s main function is to help the crab easily find a mate during spawning season.

The crabs have relatively poor eyesight, considering their many eyes. But these eyes haven’t changed in all the time of their existence, and so offer incredible insight into science and what we can learn about our own eyes.

Another amazing aspect of the horseshoe crab is its blood, which is blood. While human blood is red because of the iron in it, the crab’s blood contains copper.

The blood also contains something called amebocytes, which play an important role in protecting the crab from bacteria, viruses, and infections, much like our white blood cells do. However, unlike white blood cells, when the blood detects a foreign body, it coagulates around the invader, suffocating it until it is no longer a threat.

Scientists have found that blood harvested from a horseshoe crab can be used to detect infection in human surgical procedures, as well as in medical research. But don’t worry – taking the blood from a crab doesn’t mean killing it. They catch a crab, bleed it a little and release it back in the ocean.

As we said earlier, despite the horseshoe crab’s incredibly long history, the numbers have been declining over recent years. Some of this is down to them being caught to use as bait for eel fishing, but a part of it is also loss of habitat – an all-too-familiar story for lots of declining species around the world.

The crustaceans primarily live in shallow waters, but make their way to the shore to mate. Although they can do this at any time of year, swarms of crabs arrive on the coasts of the US in Spring to mate. Then, in May and June, the female lays her eggs in the sand and the male fertilises them. The potential parents then have to make their way back to the ocean, but the receding tide can leave some of the crabs stranded.

But help is at hand in the shape of a volunteer programme in New Jersey. “ReTURN the Favor” has been set up by a coalition of non-profit groups that enlist the help of volunteers to help rescue those crabs who haven’t quite made back on their way home.

Mating horseshoe crabs - Many get stranded on the return trip to the ocean

The programme was started in 2013, with volunteers returning in 2014 and this Spring. Last year, more than 500 people showed up to rescue almost 32,000 horseshoe crabs along Delaware Bay, which lies between the states of New Jersey and Delaware.

But New Jersey isn’t the only place hoping to help save horseshoe crabs. Biologists in Florida are also asking for the public’s help in observing the marvellous creatures. This initiative is being led by the Florida Fish and Wildlife Commission (FWC).

Kelly Richmond, FCW Public Information Specialist, said that volunteers would help provide extra sets of eyes. With more people observing the crustaceans, the FCW will hopefully be able to get a more accurate idea of how many horseshoe crabs arrive on their beaches this Spring.

“Although horseshoe crabs spawn year-round in Florida, Spring is a prime time for them to congregate and spawn along sand beaches and shallow coastal waters around the Sunshine State,” she explained.

We can learn a lot from these amazing creatures, not least of which, about their ability to survive as long as they have. And as with any creature whose numbers are dwindling, we should do whatever we can to help them survive even longer. You never know – they might yield the key to the longevity and one day return the favour.

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