Crabs save human lives!

horseshoe crab IMG_0182_1©Maria de Bruyn resOn a trip to Huntington Beach State Park in South Carolina, we took a few walks along the Atlantic shoreline. There I saw the remains of numerous horseshoe crabs (Limulus polyphemus) as their empty shells were scattered among sea pork and sea weed on the beach.

Horseshoe crabs, which can become quite large, live in shallow ocean waters on soft sandy or muddy bottoms. They occasionally come on shore to mate. Behind their five sets of legs (the remains of which are seen in the photos below), they have book gills, which exchange respiratory gases. Two gills are seen sticking up in the center of the first photo.

horshoecrab IMG_0115_1©Maria de Bruyn horseshoe crab IMG_0117_1©Maria de Bruyn res

The gills are also occasionally used by the crabs to swim, which they usually do upside down.

horseshoe crab IMG_8506©Maria de Bruyn resWhen I posted photos of my crab shell spottings on Project Noah, a fellow Noah member informed me that the horseshoe crabs are used in medicine. So I decided to read up on them and discovered how they are utilized. These crabs have hemocyanin instead of hemoglobin in their blood to carry oxygen (this colors their blood blue). Their blood also contains amebocytes, which defend these creatures against pathogens. The blood of the horseshoe crabs is harvested to obtain the amebocytes to make a product that used to detect bacterial endotoxins in human medical applications.

The US Food and Drug Administration mandates that any intravenous drugs and forms of medical equipment that come into contact with patients’ bodies must pass through horseshoe crab blood to help rule out contamination with endotoxins. This includes items such as needles, surgical implants and pacemakers.

horseshoe crab IMG_8503©Maria de Bruyn res horseshoe crab IMG_0124_1©Maria de Bruyn res

horseshoe crab IMG_0164_1©Maria de Bruyn resTo obtain the supplies, about 600,000 crabs are caught each year and drained of about 30% of their blood before being returned to the ocean. Some 10-30% of the crabs do not survive the procedure and others are injured, becoming unable to mate and reproduce. As a consequence of the harvests, these magnificent arthropods, whose lineage dates back 450 million years ago, are now becoming threatened and alternative toxin-detection methods are needed. There is a website devoted to these interesting crabs. Walks on the beach can lead to new knowledge as well as enjoyment!

A marine mystery for the uninitiated

sea pork IMG_0159_1©Maria de Bruyn resFor my friends who know me as a staunch vegetarian, it might come as a surprise that I have become fascinated with sea pork (Aplidium stellatum). It is one of the most colorful yet odd forms of sea life I have personally encountered.

My introduction to this interesting creature occurred on Topsail Island in May 2013, where I found two specimens on the beach.

Sea pork IMG_7631© Maria de Bruynres sea pork IMG_7029© Maria de Bruyn

sea pork IMG_0136_1©Maria de Bruyn res

Then, on 19 January this year, I saw some sea pork again – oodles and oodles of it, actually, accompanied by sea liver as well!

So what is sea pork, you might ask? Each blob or globule is a tunicate: an invertebrate animal that can be one individual or a collection of individuals that reproduce to form colonies measuring an inch or more in height. The larvae look a bit like tadpoles until they join to create the colonies, living in water-filled sac-like structures that are rubbery or cartilaginous to the touch.

sea pork IMG_0152_1©Maria de Bruyn ressea pork IMG_0161_1©Maria de Bruyn resThese creatures are marine filter feeders. The sacs have two tubular siphons, through which water is drawn in and expelled during feeding and respiration. The zooids extract nutrients from the water.

What are zooids? These are the reddish-colored individuals that form a colony. You can see them in circular groups under the sac’s tunic, which varies in color, including creamy pinks, orange, green, red, lavender, deep purple and black. The colonies can become large, spreading 12 inches or more and weighing up to 10 pounds.

sea pork IMG_0153_1©Maria de Bruyn res sea pork IMG_0154_1©Maria de Bruyn res
Sea pork was given this name because the rubbery tunic bleaches to white, resembling salt pork or fatback, after the colony dies. While alive, sea pork is eaten by bottom-dwelling fish, sharks and skates.

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Apparently other creatures also find a home on sea pork, including barnacles and sea whips (Leptogorgia).

Sea pork with barnacle IMG_0141_1©Maria de Bruyn ressea pork and sea whip IMG_0126_1©Maria de Bruyn resSea liver (Eudistoma hepaticum) looks similar to sea pork, but the tunic is softer. It is said to feel slimy in comparison to sea pork but the consistency seemed the same to me.

sea liver IMG_0186_1©Maria de Bruyn ressea pork IMG_0147_1©Maria de Bruyn resHowever, the difference may be more apparent when they are in their natural habitat, fastened to the sea floor or some other substrate rather than torn loose from their underground homes and cast ashore.

I spent some time throwing live sea pork back into the ocean until I came on a stretch of beach that was covered with these blobs; I hoped the tide would come in and carry the creatures back to their watery homes where they might continue their colonial lives.

 

unknown alga IMG_0177_1©Maria de Bruyn resI now have a query in to a Smithsonian marine botanist for help in identifying this organism. A scientist at the North Carolina Museum of Natural Sciences ruled it out as a marine invertebrate and said he and colleagues surmised it is a marine alga. Suggested IDs are welcome!