99 reasons I’m in ‘Limulus Love’

It’s no secret that I love those horseshoe crabs. Well someone on Twitter this week asked me why I am so crazy over them so I thought I’d take the time to outline 99 reasons I think Limulus polyphemus are a fascinating species.

  1. Three Nobel Prizes were awarded to scientists who did some or all of their research using horseshoe crab physiology.
  2. As far as the horseshoe crab’s Latin name translation, Limulus mean ‘askew’ and polyphemus is taken from a one-eyed giant in Greek mythology.
  3. The very intriguing name of Xiphosura (Greek ‘Xiphos’ meaning sword and ‘ura’ meaning tail) was given to the order of the Atlantic horseshoe crab and its three closest living related species.anatomyhsc
  4. There are 4 living species of horseshoe crabs and only one of those inhabits the western Atlantic waters – the Atlantic horseshoe crab. The other three are found in the Pacific Ocean.
  5. Samurai warrior helmets were modeled after the prosoma of a horseshoe crab.
  6. The body of a horseshoe crab (top picture) is divided into three parts – the prosoma, opisthosoma and telson (tail).
  7. Horseshoe crabs tend to be no more than 7-14” across.
  8. There once was a 50 foot long, 113,000 pound artificial reef horseshoe crab off the coast of NJ.
  9. Takeshi Yamada (pictured 3rd down) is a world-renowned artist often creating masterpieces using horseshoe crab molts.
  10. Horseshoe crabs have remained fairly unchanged over the past 300 million years (that’s 100 million years before there were dinosaurs on earth!).
  11. Horseshoe crabs are the perfect representative for Darwin’s theory that ‘the most adaptable species will prevail’.
  12. Horseshoe crabs are one of the world’s oldest animals.
  13. Before the last ice age, horseshoe crabs didn’t live much farther north than Florida.
  14. Scientists believe that horseshoe crabs (even perhaps many different species of them) were among the most dominant of animals 300 million years ago.
  15. Horseshoe crabs used to be called ‘horsefoot crabs‘ because their shell was thought to resemble a horse hoof.bcs_limuluslove
  16. Horseshoe crabs are sometimes referred to as a ‘living fossil’.
  17. Adult horseshoe crabs are often referred to as ‘walking museums’.
  18. While horseshoe crabs are opportunistic feeders, they are not aggressive animals!
  19. Most people do not understand the value of horseshoe crabs.
  20. People have organized workshops to understand bait alternatives for using horseshoe crabs to catch eels and conch.
  21. Horseshoe crabs are “the single most-studied invertebrate animal in the world”.
  22. While a horseshoe crab’s telson (tail) helps to create the appearance for an intimidating animal, they are not dangerous animals!
  23. Horseshoe crabs are so misleading – they’re actually more closely related to scorpions and spiders than crabs!
  24. Horseshoe crabs do not have mandibles, antennae, or pincers like true crabs.
  25. Native Americans ate horseshoe crab meat, used the shell to bail water, and used the tail as a spear tip.
  26. A juvenile horseshoe crab is easily identifiable because they look just like adults (see 4th picture down).
  27. Horseshoe crabs molt, or as naturalist Samuel Lockwood stated, “it is spewing itself from its own mouth”.
  28. Horseshoe crab molts are excellent shelter for mud crabs, sand shrimp, and spider crabs.
  29. A female’s lucky number is 17. That’s how many times they’ve molted before they’re ready to mate.
  30. As a horseshoe crab gets older and molts more often, they venture into deeper waters.
  31. Each time a horseshoe crab molts they grow an average on 25%.
  32. A horseshoe crab exoskeleton is made up of chitin – a material with wound healing properties.
  33. Horseshoe crabs spend most of their lives hidden.
  34. At the turn of the 19th century, horseshoe crabs were valued as a fertilizer, particularly for poultry, corn, and tomatoes.
  35. Today fishermen use horseshoe crabs as bait to catch eels and whelk.
  36. The threatened loggerhead sea turtle feasts on adult horseshoe crabs.
  37. American eel, killifish, silversides, summer flounder, and winter flounder rely on horseshoe crabs eggs and larvae for food.
  38. Horseshoe crab eggs are green.
  39. Horseshoe crab eggs are rich in fat and protein.
  40. Horseshoe crabs are big midnight snackers and love to feast on worms and mollusks.Horseshoe-crab-eggs-larvae-visible
  41. The mouth of the horseshoe crab will tickle your fingers if you’re lucky enough to have a job where you get to show people how they eat.
  42. Horseshoe crabs use their legs to chew up food and guide food into their mouths right in between their legs.
  43. Horseshoe crab legs are so strong they can crush a clam.
  44. Horseshoe crabs are expert javelinists – using their telson (tail) to act as a rudder and right itself when it tips over.
  45. The 13 pairs of horseshoe crab appendages are very multipurpose – using them for locomotion. burrowing, food gathering, and/or water flow.
  46. Horseshoe crabs use their dozen legs to swim upside down in the open ocean.
  47. Horseshoe crabs (predictably) participate in an annual orgy each May and June when thousands descend on the eastern Atlantic coastline to spawn (see fourth image down).
  48. Horseshoe crabs have a ritual of spawning during high tides of the new and full moons in May and June.
  49. Horseshoe crabs reach sexual maturity around the ages of 9-12.
  50. Horseshoe crabs tend to live a long time, usually 10 years or so after they’ve sexually matured.
  51. If horseshoe crabs can keep their gills moderately damp their survive to the next high tide in case they were to get hsc_orgystranded.
  52. Horseshoe crabs are great vessels for other animals.
  53. The highest concentration of horseshoe crab spawning on the Atlantic coast takes places along the Delaware Bay.
  54. Approximately 10 horseshoe crabs will survive to adulthood from each of the 90,000 eggs a female lays during her spawning cycle.
  55. A female horseshoe crab will lay almost 20 clutches of eggs each season.
  56. It’s a community effort making certain the eggs get fertilized. Often times many males with aggregate to a female (the males not attached are known as ‘satellite’ males.
  57. In adult males, the second pair of claws (having a distinguishable “boxing-glove” appearance) are used to grasp females during spawning.
  58. If it wasn’t for horseshoe crab eggs, many migratory shorebirds wouldn’t be able to survive.
  59. Many think there is a link between the decline in shorebird populations and horseshoe crab over-harvesting.
  60. The four most abundant species of shorebirds (relying on horseshoe crab eggs) along the Delaware Bay shore are the red knot, ruddy turnstone, semipalmated sandpipers, and sanderlings.
  61. Almost 50% of the red knot population uses Delaware Bay as mid-point stopover to consume thousands of horseshoe crab eggs. These robin-sized birds impressively travel from southern Argentina to the Canadian high Arctic to breed.
  62. The horseshoe crab-shorebird phenomenon helps to generate a large portion of the $522 million  annual ecotourism industry in Cape May County, NJ.satmenhsc
  63. The world’s leading authority of horseshoe crabs is Dr. Carl N. Shuster, Jr.
  64. In March of 2001, NOAA Fisheries Service established the Dr. Carl N. Shuster, Jr. Horseshoe Crab Sanctuary in federal waters off of the  Delaware Bay.
  65. Horseshoe crab blood is blue (see 7th picture down).
  66. Horseshoe crab blood is blue because it contains copper-based hemocyanin to distribute oxygen throughout their bodies (We use an iron-based hemoglobin to move oxygen around).
  67. Horseshoe crabs are essential to biotechnology.
  68. Horseshoe crabs are one of the pioneers in using marine organisms to save human lives.
  69. Horseshoe crabs are what we have to thank for our flu shots.
  70. Horseshoe crabs are sometimes referred to as ‘man’s best friend’.
  71. Horseshoe crabs are often captured to have their blood drained, all in the name of science.
  72. Horseshoe crabs can be released after they have their blood drained.
  73. Horseshoe crab blood cells (amoebocytes) congeal and attach to harmful toxins produced by some types of gram negative bacterias.
  74. Limulus Amoebocyte Lysate (LAL) is the name of the clotting agent made using their blood to detect microbial pathogens in medical intravenous fluids, injectable drugs, and supplies.
  75. The global market for LAL is approximately $50 million per year.
  76. The adaptation for the ability of the horseshoe crab’s blood to congeal in the presence of either living or dead gram negative bacteria has never been able to be reproduced.
  77. Horseshoe crabs have used in the development of wound dressings and surgical sutures.
  78. Horseshoe crabs have a body shape that poses difficulty for predators.wireddotcom_drainblueblood
  79. Horseshoe crabs have ten eyes.
  80. The vision of a horseshoe crab is equally as impressive at night as it is during the day with the use of their lateral eyes.
  81. With a pair of compound eyes, each with 1,000 black disks, horseshoe crabs can see to each side, ahead, behind, and above.
  82. Scientists have learned quite a bit about how human eyes function from research with cells found in horseshoe crab eyes.
  83. Horseshoe crabs have a lateral inhibition mechanism using their eyes which allows them to distinguish mates in murky water.
  84. Horseshoe crabs need a book to breathe, that is – ‘book gills‘ to be more specific.
  85. Horseshoe crab gills have small flaps resembling the pages of a book.
  86. Horseshoe crabs tell time with their tail.
  87. Horseshoe crabs have a heart that cannot beat on its own.
  88. Horseshoe crabs eat through their brain.
  89. Horseshoe crabs chase females that run away!
  90. The black disks, also known as ‘ommatidia‘, found in the compound eyes of the horseshoe crab are the largest known retinal receptors in the animal kingdom.
  91. Horseshoe crabs are able to adapt to vast changes in salinity (i.e., they’re euryhaline).
  92. Horseshoe crabs are able to adapt to vast changes in oxygen availability (i.e., they’re euryoxic).
  93. Tracking juvenile horseshoe crabs with your eyes can be a great way to spend time at the beach.hsceyecloseup
  94. You can also track horseshoe crabs and other wildlife with your iPhone while at the beach.
  95. You can get involved in helping stranded horseshoe crabs and ‘Just flip ‘em’ (see last picture).
  96. If you are a classroom teacher in Maryland you can raise horseshoe crabs as a way to increase student’s ocean literacy.
  97. Monitoring programs, like this one in Long Island Sound, are helping to advance the understanding of horseshoe crabs and their impact on humans.
  98. Development, pollution, water quality, and over harvesting have impaired the horseshoe crab’s habitat.
  99. Today and in the future we have the chance to protect horseshoe crab populations at a sustainable level for ecological and commercial uses.smilowitz

Myth debunked: Delaware Bay not an annual pit stop for all shark species

A fan of Beach Chair Scientist on Facebook recently asked me to demystify a rumor she had heard. This is what she wanted to know: “I was told that over the course of a year, at least one of every species of shark can be found in the Delaware Bay. Do you know if this is true?” I asked Jim Wharton, frequent BCS guest blogger and shark expert, to tackle this one. This is his response.

Sadly, it is not true. There are at least 500 species of sharks in the ocean. They range in size from six inches to sixty feet. They can be found in water ankle deep to the abyssal depths … from the tropics to polar ice caps. To find a nexus point like this anywhere in the ocean would miraculous. Sharks are just too diverse.

Still, there are sharks in Delaware Bay. Anglers might encounter sand tigers, sandbar (brown) sharks, smooth dogfish, and spiny dogfish with other occasional visitors (including at least one record of a juvenile white shark). In fact, the National Marine Fisheries Service has identified the Bay as ‘Essential Fish Habitat’ for several species of Federally protected ‘Highly Migratory Species’ including sandbar sharks, sand tigers, and smooth dogfish. This designation recognizes the critical foraging and nursery habitat the Bay provides for these important species.

Sand tiger shark at the Georgia Aquarium. Image (c) Underwater Times

Dr Dewayne Fox’s lab at Delaware State University is working to create a conservation plan for the sand tiger sharks in the Bay. These distinctive, snaggletoothed sharks are very popular in public aquariums. Despite their fearsome appearance, they rarely interact with people. Sand tigers are top predators and represent a critical keystone species in the ecology of Delaware Bay. Dr. Fox and his students are implanting passive acoustic transmitters inside sharks to better understand their movement patterns. The transmitters emit an identifiable ‘ping’ that is collected by strategically located listening stations to help researchers track the animals in the Bay. Understanding how the sharks use the Delaware Bay is essential to identifying critical habitat for protection. You can learn more about Dr. Fox’s work here.

Sand tigers, by way, are freakish and fantastic creatures that are well-worth saving. No sharks have swim bladders, but sand tigers gulp air at the surface to make themselves neutrally buoyant. Sand tigers are one of many species that explode the myth of the shark in constant motion, frequently found lying near-motionless on the sandy bottom. Sand tigers are fish-specialists, with more-than-a-mouthful of narrow, prong-shaped teeth for grabbing slippery prey. They like to hang-out in large aggregations and may actively cooperate to herd schools of fish. Most fantastic of all…baby sand tigers are “embryonic cannibals.” Sand tiger embryos quickly exhaust their meager yolk sacs and start in on the undeveloped eggs…but they don’t stop there. The largest embryo in each uterus (yes, sharks have two) attacks and consumes its brothers and sisters in the ultimate form of sibling rivalry.

Good references for more on sand tigers:

  • Castro, J. I. (2011). The sharks of North America. Oxford: Oxford University Press.
  • Compagno, L. J. V., Dando, M., & Fowler, S. L. (2005). Sharks of the world. Princeton: Princeton University Press.

Thanks for sharing you knowledge, Jim! Check out his other BCS posts on sharks here.

A naturalist’s must-see destination: Cape May County (and, the rest of south Jersey)

Earlier this year I was happy to see that the federal government had awarded New Jersey a $1 million grant to protect the ecologically sensitive wetlands in Cape May County (“Where Nature Smiles for 30 Miles” and where my hometown is located). The New Jersey Department of Environmental Protection (DEP) will use the money to purchase 140 acres to add to the existing 17,000-acre Cape May Wetlands Wildlife Management Area. These wetlands are not only where I fell in love with the natural world, but are also home to many species of migratory birds and act as a nursery for many commercially important species of fish that spawn in the estuaries.

So with a combination of my pride in the DEP’s award and my feelings that an ‘ode to home’ in the Where We Live series is long overdue, I decided to take the time to compile a list of “10 unique and interesting natural history or maritime features of south Jersey”. I am sure there are plenty more out there, so please feel free to comment below or send me an email at info@beachchairscientist.com if you have any additional comments or questions.

1. South Jersey sits to the east of the Delaware Bay. The Delaware Bay boasts the second-highest concentration of shorebirds in North America (second to Quivira, Kansas which is mid-point in the United States). The Bay is mid-point in travel for many birds that travel from the warm weather of South America up to the Arctic. The Bay is also a perfect wintering habitat for many species of songbirds and waterfowl.

2. The world’s largest population of Atlantic horseshoe crabs (Limulus polyphemus) spawn in Delaware Bay.

3. At the entrance of the Delaware Bay is the Cape May Lighthouse, built in 1859, which documents the beginning of Cape May County’s nautical history. There is also the Hereford Inlet Lighthouse, built in 1874, on the Atlantic Ocean side of the Cape May County peninsula in North Wildwood. Speaking of Cape May, the famous Cape May diamonds people have been looking for since the 1880’s are actually quartz crystals that wash up as smooth rock.

4. At 3800 Boardwalk Mall in Wildwood you can see the 43rd Wyland Whaling Wall, “Humpbacks off the Jersey Coast” (pictured right). Wyland is known as “one of America’s most unique creative influences, and a leading advocate for marine resource conservation”.

5. The A.J. Meerwald, New Jersey’s official Tall Ship, began life as a sailing schooner built for oystering,  but was commandeered during World War II to serve as a fireboat on the Delaware Bay.

6. The Stone Harbor Point is one of the few parcels of New Jersey’s coast that has not been stabilized (86% of the shoreline has been stabilized) leaving a remarkable wide open space that has been shaped (and reshaped) by waves and tides for centuries. It also has one of the last thickets of bayberry left on New Jersey’s coast.

7. The Marine Mammal Stranding Center in Brigantine has the impressive achievement of responding to over 3,900 strandings of whales, dolphins, seals, and sea turtles (all, of course, done with a permit and authorization from the state and federal governments).

8. In south Jersey you’ll also find the Pine Barrens, a distinctive natural area spanning over  1 million acres of the Outer Coastal Plain (pictured left) in southern and central New Jersey. Dr. Witmer Stone, an early New Jersey natural scientist described the area as “always sandy and thickly covered with more or less scrubby vegetation, interspersed with swamps and infested by hordes of mosquitoes”. This area is particularly prone to fires and some species, such as the rare pygmy Pitch Pine, have become adapted to the fires and count on the fires to reproduce. The sandy soil of the Pine Barrens is sometimes referred to as sugar sand.

9. Blueberries were officially named the state fruit in 2004. New Jersey produces the second most blueberries in the world (Maine is first). Hammonton is considered the “Blueberry Capital of the World”.

10. After the federal government designated the Outer Coastal Plain as an American Vinticultureal Area, south Jersey started up on the wine trend! Now south Jersey has more than 20 fully functioning wineries and vineyards.

As Jacques Cousteau said, “People protect what they love“. I am sure you can tell from this blog that I do love the ocean. This love no doubt came from growing up in south Jersey and spending time everyday at the beach or the nearby Bay.  Here’s a poem I wrote (almost 12 years ago) about the area. I hope you’re inspired to learn about the natural history of your own area – especially on this upcoming Earth Day weekend.

Cheers!

Atlantic horseshoe crab infographic

Whether we know it or not, the Atlantic horseshoe crab has made a significant impact on many of our lives. The significance of this living fossil can be found in its capacity to resist change for millions of years, its special copper-based blood is crucial to the medical field, and its ability to provide food for millions of migratory birds year after year.

Where have all the horseshoe crabs gone?

If you’ve kept on eye on the sandy shores of the Atlantic Ocean or eastern Gulf of Mexico over the past twenty years you’ve noticed a significant decline in the number of horseshoe crabs, Limulus polyphemus, covering the beach. As a marine educator and naturalist in my past life, I always said the decline was due to over harvesting for bait and pharmaceutical needs. This is only half the reason. Recently scientists also noted that climate change, with the sea level rise and temperature fluctuation, may be a cause of the decline.

Tim King, a scientist with the United States Geological  Survey, thinks that what happened during the Ice Age could happen again. With climate change comes a loss of habitat and a loss of diversity. These issues could have severe implications, not only for horseshoe crabs, but also for species that rely on them for sustenance. For instance, along the Delaware Bay the red knot eats the horseshoe crabs eggs at the midpoint of their migration. In the Chesapeake Bay, loggerhead sea turtles are struggling to find one of their favorite food sources, horseshoe crabs, and are retreating elsewhere to find food. Now that the link of a decline in the horseshoe crab population and climate change has been made fisheries managers can take this into consideration.

Images (c) Greg Breese, US Fish and Wildlife Service