Search Results for: horseshoe crabs

My awesome, overprotective mom and horseshoe crabs

limuluslove_beachchairscientistwebNo joke. I like horseshoe crabs, but not more than my family. Especially my mom. Let me tell you a story about how incredible she was one particular evening in early June. It was probably about 2002 and I was a seasonal employee for the NJ Division of Fish and Wildlife. The job was awesome in every sense. Except the hours … either really early for tagging stripers along the Delaware Bay or really late to survey HORSESHOE CRABS!

In case you haven’t heard watching the horseshoe crabs come up to the wrackline to spawn is an incredible experience (check out my post on the short and sweet of horseshoe crab spawning here). You might see some Limulus polyphemus the nights near a full moon or new moon right as the sun is going down. But, it’s not until the tide is at its highest point that the ancient fossils really come out of their hiding spots. 2.IMGP1651-Photograph-James-Bulley-1024x680My co-workers and I went about as normal for this event and used the  quadrat to estimate the amount of females and males every six steps (the females are much bigger!). We’d log the numbers on a clipboard. After the length of the beach that was our responsibility we’d head home. It was about 2am one particular morning when we finally made it back to the van. I also worked as a waitress in the summer so it had been a long day. The data sheet was my responsibility. It blew away. It’s really windy by the sea usually!

We didn’t fudge any numbers. I went back the next night … but, not alone. My amazing, overprotective mom came with me. After all, I had to drive about an hour to a small town along the Delaware Bay in the middle of the night. It was going above and beyond. I mean, she’s not a nature-type so this was in pure mama bear mode that she made the trek with me. It was incredible … my mom was totally amazed by the phenomenon too. One minute there were about fifteen horseshoe crabs and the next hour as soon as high tide occurred they were covering the beach! That night I was able to share my love of teaching and horseshoe crabs with someone I loved. She exuded such enthusiasm that I have no doubt it’s one reason I keep this blog and it’s focus of all things horseshoe crabs going. She might have been pulling my arm and thought the whole experience was really gross and icky, but parents know how to let their kids shine and that’s just fine with me.

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NOAA’S Ocean Today provides a great view of the field experience, too. Yes, I did wear a headlamp like those citizen scientists.

What citizen science projects have you participated in lately? Check out what’s going one here.

Do all horseshoe crabs molt?

Once a horseshoe crab reaches their full size they stop molting. Their shells then come to host many sessile creatures, including slipper snails.

Once a horseshoe crab reaches their full size they stop molting. Their shells then come to host many sessile creatures, including slipper snails.

All horseshoe crabs molt – until they reach adulthood. They grow on average a quarter of their size each time they shed. Females grow to be about two feet across and males a bit smaller. Molting occurs several times during the first few years and slows as they age. It usually takes 17 molts to reach sexual maturity  at age 9-11.

Studies have proven that adults do not molt because the age of organisms living of the crab’s shell. For instance, scientists Bottom and Ropes (1988) completed a study to determine that large slipper snails (Crepidula fornicata) were at least 8 years old on a sample of specimens. This would then make the average age of horseshoe crabs in the Delaware Bay to be 17 years old.

Also, the deteriorated carapace of some horseshoe crabs, as well as the presence of internal chitinous rods that hold the carapace in place are also evidence that older horseshoe crabs do not molt.

Why is the blood of horseshoe crabs blue?

Horseshoe crabs use hemocyanin to distribute oxygen throughout their bodies. Hemocyanin is copper-based and gives the animal its distinctive blue blood. We use an iron-based hemoglobin to move oxygen around.

The blood of this living fossil has the ability to  clot in an instance when it detects unfamiliar germs, therefore building up protective barriers to prevent potential infection. This adaptation has made the blood of the horseshoe crab quite desirable to the biochemical industry.

Image (c) wired.com

How have horseshoe crabs been able to remain unchanged for centuries?

In case you have not had the opportunity to get your hands on the new book, Horseshoe Crabs and Velvet Worms, about animals that have remained unchanged through time (Richard Fortey) here is a video from the BBC  on how the horseshoe crab has been able to survive through the ages.

I am particularly fond of this clip because the horseshoe crab expert notes that the horseshoe crab, while an opportunistic and a generalist, is not an aggressive animal.

Please feel free to comment if you’re one of the few that has eaten horseshoe crab eggs.

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

Why are horseshoe crabs essential to biotechnology?

First of all, let’s chat biotechnology, or, ‘biotech’, as those in the industry call it.

The concept of biotech has been around for ages, just, not given the fancy term. For instance, planting seeds to produce food, fermenting juice for wine and churning milk into cheese are all processes that use some derivative of a plant or animal to benefit mankind. In the biotechnology and pharmaceutical fields of today, the Atlantic horseshoe crab (Limulus polyphemus) blood is a very important component in the process for testing drugs that can benefits humans.

Their blood is used for the  Limulus Amebocyte Lysate (LAL) test is used to test for gram negative bacteria contamination in certain products before being released to the public. Horseshoe crab blood cells (amoebocytes) attach to harmful toxins produced by some types of gram negative bacterias. What is unique with the LAL, is that LAL does not distinguish between living or dead gram negative bacteria and detects either.

You do not want anything with a gram negative bacteria contamination. Gram negative contamination include: Escherichia coli, Salmonella, Neisseria meningitidis, Hemophilus influenzae, Klebsiella pneumonia.

The blood of the horseshoe crab has this unbelievable property where it will congeal in the presence of either living or dead gram negative bacteria (both are undesirable). This adaptation has never been able to be duplicated and consequently horseshoe crabs are often captured to have their blood drained and then released, all in the name of science.

Do you have another great question? Check out www.beachchairscientist.com and let us know what you always ponder while digging your toes in the sand!

Are horseshoe crabs dangerous?

No. I mentioned in the very first BCS blog entry that the horseshoe crab is a “sweetheart of an animal” and I will continue to defend that statement. Some people may think that the tail spine, or telson, is poisonous. What the telson is simply used for is to flip the animal over when a wave turns it onto its carapace. The tip of the telson is jabbed into the sand and the horseshoe crab rights itself over, somewhat like the act of throwing a javelin.

Do you have another great question? Check out www.beachchairscientist.com and let us know what you always ponder while digging your toes in the sand!

The short and sweet of horseshoe crab spawning

You may have heard about the phenomena of horseshoe crab spawning … but, do you really know what’s going on? It’s when hundreds of thousands of these ancient arthropods (dating back 400 million years!) make the journey to low-energy sandy beaches along the Atlantic coast, predominately along the Mid-Atlantic region (highest concentration found along the Delaware Bay), around the time of the full and new moons of May and early June to spawn. Here’s the distilled version of the horseshoe crab spawning saga complete with the words you need to know (i.e., “pedipalps” and “satellite” male) if you want to be considered a horseshoe crab expert. Who doesn’t?

https://www.flickr.com/photos/beachchairscientist/

https://www.flickr.com/photos/beachchairscientist/

  1. Journeying from intertidal and deeper waters, male horseshoe crabs arrive near the beach waiting for females.
  2. As the females come closer to shore, males attach to the female’s abdomen. The extra claw, or “pedipalps”, is what the male uses to attach itself to the females.
  3. Not just the one … but, many “satellite” males follow the conjoined pair.
  4. The females dig a depression about 5 to 30 centimeters deep in the upper part of the beach and deposit the clusters of eggs.
  5. External fertilization occurs – Allows for a little extra competition from the “satellite” males!
  6. Repeat steps 1 through 5 multiple times per season, laying 3,650 to 4,000 eggs in a cluster (usually an estimated 88,000 eggs annually!).
  7. In 2 to 4 weeks after fertilization, planktonic larvae hatch from the eggs. Some slow moving larvae may even winter within the nests and hatch out the following spring.
  8. After hatching, larvae swim for about six days before they relax in shallow waters to molt into their first juvenile stage in approximately 20 days.
  9. For the first two to three years of life horseshoe crabs molt many times over, growing a quarter of their size each time. Once sexual maturity is reached they slowdown their molting to once per year.
  10. Horseshoe crabs mature around 10 years of age (or 17 molts) and are known to live to be approximately 20 years of age.

For more information on horseshoe crabs and “99 reasons I am in Limulus Love” check out my horseshoe crab page here.

Horseshoe Crab Round Up: May 2013

And, we’re concluding the first month of the horseshoe crab mating season for 2013. Over the past couple of weeks, many articles have come through the great worldwide web including some new creative introductions on the relationship of Limulus polyphemus and shorebirds, captivating expose on the capture of two horseshoe crab poachers, updates on the plight of the species after Hurricane Sandy, the discovery of a new bait that could reduce the horseshoe crab harvest, and even a information on raising awareness of the role horseshoe crabs since they play a role with QC endotoxin detection tests (but, read more to see that there may be a sustainable alternative). If you have anything other interesting reads for May please post a comment below.

Limulus polyphemus and Shorebirds (including efforts on tagging, etc)
Journey of shorebirds, horseshoe crabs to shore linked through the ages – May 1, 2013
Protecting ancient undersea creatures – May 9, 2013
Being ‘crabby’ might benefit mankind – May 10, 2013
Tagged Horseshoe Crabs at Big Egg Marsh Queens NY… – May 25, 2013
Shorebirds, Horseshoe Crabs and Stewards… – May 26, 2013
Volunteers help tag mating horseshoe crabs on Harbor Island – May 28, 2013

 

The Poaching Adventure
2 arrested for poaching horseshoe crabs from NY – May 28, 2013
It’s Dark, but We See You: Release the Horseshoe Crabs – May 28, 2013
NYPD Busts Horseshoe Crabs Poachers After Chopper Chase – May 29, 2013

After Hurricane Sandy Habitat Restoration
Restoring hurricane-damaged horseshoe crab spawning beaches on Delaware Bay – May 11, 2013
Workers race nature to rebuild Shore habitats before mating, migration season – May 20, 2013
After Sandy, a race against time to save an endangered shorebird – May 25, 2013

New Bait Alternative for Eel and Whelk
New bait may cut horseshoe crab bait use – May 30, 2013
New artificial bait could reduce number of horseshoe crabs used to catch eel, whelk – May 30, 2013

QC Endotoxin Detection Tests
Lonza Not ‘Shellfish’ When it Comes to Endotoxin QC Testing – May 21, 2013

The world’s horseshoe crab research finally finds a home

This month the Ecological Research & Development Group (ERDG) released a one-stop-shop for research, conservation, and education initiatives on the world’s four species of horseshoe crabs. This was a result of the discussions from the 2011 International Workshop of the Science and Conservation of the Asian Horseshoe Crabs held in Hong Kong.

Be sure to check it out today. There’s lesson plans, peer-reviewed articles, posters, PowerPoint presentations, and more. It’s the intention of the database to serve as a tool to benefit everyone who is in Limulus Love!

I was surprised to learn that the new database includes over 2,000 citations and ERDG is still looking for more materials from people like you and me (Maybe, I’ll submit my cheesy infographic).

Horseshoe Crab Research Database http://horseshoecrab.org/research/

Horseshoe Crab Research Database created by the Ecological Research & Development Group