Horseshoe Crab: Monster or Miracle

This post was insired by a Twitter conversation I had with @oceanshaman and by the fact that it is one of many creatures that I was terrified of as a kid, but as I learn more, I realize my fears are unfounded.

I went to North Carolina with about 20 other family members every summer for a handful of years. I played in the water a lot, but was completely terrified of anything that moved and lived in the ocean–fish especially. But one afternoon while waist-deep in the water, I felt something crawl over my left foot and by the time I had looked down, it was going over my right one.  As soon as my foot was free of its prickly, slow gait, I fled the water screaming to seek refuge at my ‘safe’ beach towel. 

What Is A Horseshoe Crab?

Like many things, this creature is misnamed. It is not a true crab, but

more closely related to spiders, ticks, and scorpions.  It is a remnant of its ancient lineage and hasn’t physically changed much for 250 million years.  In fact, their shape is really the only thing that resembles a crabs, who have gills while these ‘crabs’ have book lungs. 

In fact, its taxonomy explains this creature very well:

Phylum: Arthropoda Subphylum: Cheilcerata Class: Merostomata Subclass: Xiphosura  Order: Xiphosurida  Family: Limulidae
Genus: Limulus Species: polyphemus

…Or a joint-legged animal with no jaws having a mouth surrounded by legs and a sword-like tail with one living member left in the family having large compound eyes on the sides of its head.

Sounds like I just described a monster, doesn’t it?  It fits perfectly with the creature I felt crawling over my foot. But this fierce, primative-looking creature from the deep is nothing more than a worm slurper.

Dangerous or A Passive Predator

Remember reading above that this creature had no jaws and a mouth surrounded by legs? With this in mind, I am sure you are thinking that it would be rather difficult to chew. Indeed! When a horseshoe crab crawls over the sandy bottoms, it senses worms and mollusks with its claw-tipped feet. Once a food item is found, it picks it up with those claws, passes it to where its legs meet its shell.  Once there, the legs rip up the food as the horseshoe crab walks and the food bits that make it to the bristles near its shell are eventually passed to the mouth to be consumed. The horseshoe crab also has a gizzard-like organ in which sand helps further grind up the food. 

Book gills are to the right

So all the armor and fierce decoration on this creature works more as a deterrent than as a weapon.  The little claws on the end of the legs are not strong enough to break a person’s skin and since it has no jaw, it can’t bite, but it is possible to get pinched by placing your fingers near where the legs meet the body. The tail looks sharp as if it were the same as a stingray, but if you watch a horseshoe crab for a while, you’ll see the tail is necessary for maneuvering in the sand and surf. In fact, this creature is docile enough to keep in aquarium touch tanks that you can find across the country.

Interesting Features

It’s often stated that horseshoe crabs have 10 eyes, but more specifically they have one set of compound eyes, which look most like eyes to us, and a pair of simple eyes towards the front of the shell and then a collection of light sensing cells scattered around the top. In total, areas that can ‘see’ and detect light equal ten, but not ten blinking eyes that most people picture.

It’s really easy to tell males and females apart. Females, for one, are much larger than their male counterparts, but to be sure flip the crab over and look at the first clawed foot.  If it looks like they rest of them, then it’s a female [or maybe an immature male].  But if the first claw looks like an oven mit or boxing glove, then it’s a male.  He uses this specialized claw to hang on to an egg laying female while she digs holes in which to deposit her eggs. As the male is along for the ride, he is pulled over the newly deposited eggs and fertilizes them. It takes almost a decade for horseshoe crabs to mature.

Important–Of Course!

Since there really isn’t anything to worry about when handling a horseshoe crab and it only eats worms and other invertebrates, is there really any reason to worry about this creature?

Indeed, there is! As an important spoke in the food web, the horseshoe crab serves as a food item for many creatures, as do the eggs of the horseshoe crabs and the larvae that briefly float around in the water column. Birds, fish, and crabs eat the eggs and larva of the crabs and adults are eaten by sea turtles.  Not just a food source, they also house many creatures, from barnacles to worms in their gills. Though not listed as endangered, they do warrant protection.

But if you’re not interested in who eats whom out in the deep, then maybe this will be of interest.  In some states you are not allowed to harvest horseshoe crabs except to allow for their blood to be drawn.  Their blood is used in standard testing for detecting impurities in our IVs and other medical fluids. They don’t go and bleed the horseshoe crabs dry, though. They catch wild individuals, draw some blood, and then release them back to the same location from which they were caught.  So if you’ve ever been to the hospital, you have a horseshoe crab to thank for not getting any microbial infections from your IVs!

Sources/Good Reads:

Horseshoe Crab Biology

Horseshoe Crabs, SCDNR

Horseshoe Crab.org

Scenic Sunday: Living Beach

For more beautiful photography, please visit Scenic Sunday!

You’ll be glad you did!

Beaches are beautiful places, that usually goes without saying, but when you sit on the beach, you aren’t alone, even if you see no other being in sight!

The beach is teeming with interstitial microorganisms, little microscopic creatures that call home the space found between sand particles. But you don’t need a microscope to see other inhabitants that often go unnoticed for there are many just below your feet and the waves!

This little fellow below is called the Sea Pansy, although to me it looks like just one petal from a pansy or more like a leaf.  Hard to believe, but it’s related to corals and anemones with its closest relative being the sea pen.  Like coral, it is a colony, a whole colony, of polyps. These creatures are bag-shaped generally with one end open and the other attached to a surface [think of an anemone, a single bag-shaped polyp attached to the surface at one end and open with tentacles at the other].

The Sea Pansy, being a whole community working together as one, has a number of different polyps doing different jobs.  The ‘stem’ or what anchors the Pansy down is actually one long polyp. Within the body are a bunch of little polyps with some that do resemble their larger cousin the anemone in shape, with tentacles that protrude from the face of the Pansy and filter particles of food. Unlike the garden variety, this Pansy doesn’t sit upright, but lies flat on the sand.

The *coolest* part is that these seemingly lifeless blobs of goo are bioluminescent! If you can find it at night, poke it! It will light up [kind of like a lightning bug]!! Look for these guys in the swash.

Another neat creature is the Commensal Crab. These small crabs, usually less than an inch or two, live commensally with other creatures. One well known crab is the Oyster Pea Crab; the smallest in this area is the Sand Dollar Crab. The names of these two indicate where these guys prefer to live.  There are also species that like to live with scallops, tube worms, etc. and all appear quite similar, so apologies for not knowing who this fellow is below! I think he’d rather not be on that shell anyway…gives you reason to pause before stepping on or driving over shells!

These are carapaces, the shell on the back of a crab. I would have liked to find the whole crab alive, but these fellows live offshore and are dubbed the swimming crabs because of their paddle-shaped back legs and their method of motion.

The one above is the Ocellated Lady Crab and the one below, as distinct as it is, I can’t find the name for, do you know???

I’m thinking some kind of box crab…

This neat thing is a Moon Snail sand collar, or an egg case.  There are little tiny eggs sandwiched between sand particles. When wet, the thing is gooey and flexible; when dry, it crumbles like dry sand.

Hope you enjoyed reading that as much as I enjoyed researching it! Thank you for visiting!

Sources and Recommended Reading:

Ruppert, Edward E., and Richard S. Fox. Seashore Animals of the Southeast: a Guide to Common Shallow-water Invertebrates of the Southeastern Atlantic Coast. Columbia, S.C.: University of South Carolina, 1988. Print.

Hayes, Miles O., and Jacqueline Michel. A Coast for All Seasons: a Naturalist’s Guide to the Coast of South Carolina. Columbia, S.C.: Pandion, 2008. Print.

Washed Up

DISCLAIMER:  Graphic pictures are included below.  View accordingly!

I’m going to admit something awful and shameful here……I occasionally touch dead things!

Disgusting and dirty, I know!  But sometimes, it’s the best way.  If you’re a naturalist-type, then I’m sure you’ve at least had an inkling to do the same.  Unless you work hands-on with wild animals, dead critters are all you’ve got to work with. 

Now, don’t get too freaked out and let your imagination get the better of you!  I’m not talking about gory dissection and mutilation, just observance of an animal that usually wouldn’t hold still for such close inspection.

I’ll admit that this started at an early age.  The first animal I remember handling was a cardinal.  It crashed into my great grandparents’ window with an always-surprisingly-loud-for-such-a-small-creature thud.  He was a beautiful male, still breathing, but his head rolled around limply.  I remember sticking him in a box filled with pine needles from the ‘magic forest’, thinking he would somehow magically mend.  He didn’t, of course, and probably spent his last minutes either in shock or freaking out that this 8-year-old was going to eat him.  Poor fellow.

Despite his sad demise, I remember the feel of his feathers, the sharp point his little beak, and most of all, his odd, reptilian-looking feel with his long, curled claws. 

Just holding that bird for a few minutes and observing helped reinforce that connection with nature that so many fear is missing in today’s new generations. 

Even working as a park ranger, I observe the same cardinal-in-the-hands type of experience with visitors, young and old, when they touch bison and pronghorn horn sheaths, the fur of a prairie dog, or a 30 million year old fossil.  Observation is one thing, but hands-on experience is another. 

In keeping with this theme, though a little morbid, I’m posting a couple of pictures of what washed up on the beach the other morning after a little storm system blew threw.  It doesn’t take long for anyone visiting a beach to realize that some odd things wash up after storms, and to me, it’s much preferable to jumping in and chasing after all those sea creatures [did I mention I have a slight fear of large fish?!]. 

Mind you, I didn’t touch ALL of these, just a couple.  Wouldn’t want to gross out the husband enough to receive divorce papers!

This is an odd fellow, perhaps a variagated urchin, perhaps not.  Rather tiny either way, probably not all that old, and I thought he might still be alive in there, so I put him back in…but not before taking a picture!

I think this might have been a jellyfish, but I’m not 100% sure it isn’t man-made.  Either way, it caught the evening light in such an odd way.  It if is a jellyfish, my guess is it’s only a part of one, perhaps the some inner, harder core.  Truthfully, I have no idea, but it’s fun to ponder!

This one tells a story.  The little crab leg in proximity to a bunch of scuffle marks in the sand with a nice large hole probably indicate that there was a crab hiding there, some predatory, oportunistic bird or other creature spotted the crab and yanked him from the hole and gobbled him up. 

I’ve spoken with people who just shrug their shoulders at such small things.  I always ask them to imagine themselves as crabs, walking along on a nice beach and you come across your neighbor’s leg and if  they can’t do that, then imagine that was a human leg instead of a crab leg.  A little extreme, but it changes perspectives.

Speaking of extreme, I apologize for the extreme gore of this picture.  Didn’t think I’d find something like this, but there he was.  A male wood duck, in beautiful breeding colors, that became something’s dinner.  Not sure if that was before of after he fell in the ocean, but the reason I found him was because one of his distant relatives was picking at him.  After taking the picture I let the seagull have his dinner back.  Hey, there are tribes in the world that consume monkeys. 

This one hits a heart string.  Poor little juvenile pelican didn’t make it through his first season.  Last time I went to the beach he was still there…anyhoo, getting all teared up.  The hook on the end of his beak is pretty amazing.  It is as hard as granite [probably not literally] and I’m guessing it’s made of the same thing our fingernails are. 

Alright, that’s enough for now.  Apparently life isn’t a guarantee for anyone or anything.