Learn a lot about horse­shoe crabs

Maryland Independent - - Sports - Jamie Drake

When I was grow­ing up my fam­ily would go to Ocean City ev­ery sum­mer for a fun­filled va­ca­tion at the beach.

Even af­ter a whole week of surf and sun, we were never quite ready to go home when it was time, so my dad would drive us up to Re­hoboth Beach on the way out of town and we’d check out their beach and board­walk for some last minute fun and lunch at Grotto Pizza.

One year, on the morn­ing of our last day at the beach, my sis­ter and I found a trove of dead horse­shoe crabs washed up on shore. Think­ing it was a good idea to bring them home with us, we col­lected as many as pos­si­ble in our beach tow­els and stowed them in the back of my mom’s car. As we drove to Re­hoboth for lunch that day, the mer­cury started ris­ing. It was go­ing to be a hot one.

The horse­shoe crabs baked for sev­eral hours in the blis­ter­ing sun in the back of my mom’s car while we ex­plored the beach and ate lunch. When we were fi­nally ready to drive home and opened up the car, the stench that greeted us was too foul for words. My dad dis­patched of the of­fen­sive car­casses im­me­di­ately and we drove home with the win­dows down, try­ing not to gag too much. Our great idea prob­a­bly cost my mom a few hun­dred dol­lars when she traded in her car a cou­ple years later. The smell lin­gered.

Since then, I’ve never had too much of an in­ter­est in horse­shoe crabs. My fam­ily and I have seen them on oc­ca­sion at the beach and had the chance to han­dle the spec­i­mens at the Calvert Ma­rine Mu­seum in Solomons. We are aware they are liv­ing fos­sils, rel­a­tively un­changed since be­fore the time of the di­nosaurs. And that long spiked tail? It’s not a stinger. Horse­shoe crabs are harm­less and the tail is used by the crab to flip it­self up­right if it gets turned over.

But horse­shoe crabs have quite an in­ter­est­ing story. Ear­lier this month, the South­ern Mary­land Audubon So­ci­ety spon­sored a field trip to Flag Ponds Na­ture Park in Lusby and I tagged along to learn more about this funny look­ing crea­ture.

This wasn’t just any field trip ei­ther, it was a night­time ad­ven­ture that started at 9 p.m. on a Sun­day night. I wasn’t re­ally think­ing things through when I in­vited my 5-year-old daugh­ter to ac­com­pany me on this out­ing that started just af­ter her bed­time.

We met up with nat­u­ral­ist Andy Brown who knows a lot about horse­shoe crabs, and a lot about birds and na­ture in gen­eral. He started off the night by ask­ing the au­di­ence if any­one knew what an arach­nid is. A lot of hands shot up and some peo­ple shouted out “spi­der,” but there were some con­fused looks from a few peo­ple who won­dered if they were in the right place.

As it turns out, horse­shoe crabs aren’t crabs at all. They are part of a group of an­i­mals closely re­lated to the arach­nid fam­ily. There­fore their cousins are more likely to be spi­ders and scor­pi­ons rather than lob­sters and true crabs. That’s some­thing I didn’t know. But just like Mar yland’s most fa­mous crabs, horse­shoe crabs have to molt to grow big­ger.

Horse­shoe crabs have blue blood. And, no, I don’t mean they are re­lated to Prince Wil­liam and Princess Kate. Their blood is ac­tu­ally bright blue. Brown handed around a vial of the blue stuff and asked us to be very care­ful. Horse­shoe crab blood has a lot of med­i­cal prop­er­ties that make it quite valu­able, with a price tag of about $15,000 for just one quart. That lit­tle vial prob­a­bly con­tained a few hun­dred dol­lars worth of horse­shoe crab blood.

We were cu­ri­ous just how horse­shoe crab blood is col­lected. There are no farm-grown horse­shoe crabs to do the job, so wild ones are caught and about 30 per­cent of their blood is har­vested. Then they are re­leased back into the ocean. Each year about a quar­ter of a mil­lion horse­shoe crabs do­nate their blood so med­i­cal de­vices and vac­cines

are safe for hu­man use.

Lately, sci­en­tists are won­der­ing if this prac­tice is harm­ing the horse­shoe crab pop­u­la­tion. It is es­ti­mated that up to 30 per­cent of crabs don’t sur­vive af­ter be­ing bled, and the har­vesters re­lease the horse­shoe crabs far from where they were cap­tured to avoid re­cap­tur­ing and bleed­ing them again.

I can’t imag­ine be­ing forcibly moved to a new ter­ri­tory is very good for a crab’s sur­vival.

A tag­ging pro­gram is now in place to keep track of ex­actly where the crabs live and spawn. While their nat­u­ral range spans the en­tire east coast, the tag­ging pro­gram has shown that some crabs re­turn to the same beaches year af­ter year to spawn. That’s pretty in­cred­i­ble.

And the rea­son the Audubon So­ci­ety takes

an in­ter­est in horse­shoe crabs? Their eggs pro­vide the fuel for thou­sands of mi­grat­ing birds each year. The red knot, a bird that mi­grates 10,000 miles from Ar­gentina to the high arc­tic to breed, stops off in Delaware Bay to gorge on eggs at the peak of the horse­shoe crab spawn. With­out the

horse­shoe crab eggs to feast upon, th­ese birds wouldn’t have the en­ergy re­serves to make such a long and ar­du­ous trip. It’s amaz­ing how na­ture is in­ter­con­nected.

Af­ter talk­ing about horse­shoe crabs for a few min­utes, the group walked about a mile down to the edge of the Chesapeake

Bay. The moon wasn’t full, but there was enough light so we could see our way on the beach with­out flash­lights, which is a good thing be­cause horse­shoe crabs have 10 eyes that are light sen­si­tive.

The wind was whip­ping that night which made the surf rougher than ideal, but we still found a few fe­male

horse­shoe crabs bur­row­ing in the sand to de­posit their eggs. The male crabs, which are sig­nif­i­cantly smaller than the fe­males, will con­gre­gate around a fe­male in hopes of fa­ther­ing some of the off­spring. But we only saw pairs of crabs that night.

jamiedrake­out­doors@ out­look.com

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