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Amazing horseshoe crabs
- 1. Everything you ever wanted to know
- 25. Thank you to the Maryland Department of Natural Resources for providing the slides with the blue background.
Editor's Notes
- The majority of the breeding beaches are located from New Jersey to Virginia, so we are right in the middle of the largest populations.
- Horseshoe crabs are more related to Spiders, Ticks and Scorpions
- The Horseshoe crab’s tail is called the Telson. Never pick one up by the tail, it may pull out or become dislocated. Pick them up by their shells.
- http://youtu.be/sCtAv7fU1lc?hd=1 This links to a Youtube video of a horseshoe crab swimming. You can really see the book gills in action.Talk about the fact that Horeseshoe crabs breathe through gills. Their gills have to stay wet when they come up on the beach.
- ACTIVITY:The Lateral eye is a compound eye (like a fly) It is most like ours. The other eyes see primarily light and dark or ultraviolet light. Our little crab’s compound eyes don’t work very well yet. But they will be fully functional when they grow up and are looking for prospective mates.Range of vision. 2 volunteers. Have one person walk around another and stop when they can’t see their eyes.Have volunteer walk around horseshoe crab and stop when they can’t see their eyes.
- Each horseshoe crab compound eye has 1000 lenses. The link http://www.youtube.com/watch?v=2SBOKcuVHDo takes you to a little documentary on how horseshoe crabs see with their compound eye.A horseshoe crab can see 360 degrees around itself (so it can see behind him without turning).
- The male attaches to the female’s shell with his pedipalp.
- Horseshoe crabs come up on the beach to lay their eggs. In our area, they do this in May or June depending upon the weather. They tend to lay their eggs during the Full Moon or the New Moon because tides are highest then. While they are doing this they have a tendency to dig up each other’s eggs by mistake.In a season, a female will lay about 88,000 eggs.
- This is Miss Joan. She was vacationing at a Maryland beach at the height of horseshoe crab mating season. The green thick carpet in front of her are horseshoe crab eggs!
- http://youtu.be/x-KEYpohcRY?t=1m57s This leads to a youtube of an artist’s conception of how the earth looked 500 million years ago.Notice that there are no plants or trees, no animals or insects. Why might it be a good idea to lay your eggs here?
- Young horseshoe crabs spend their time in shallow water and move deeper out to sea as they get older. No one is sure what horseshoe crabs do when they are not on the beach laying eggs. This might be a good research project if you want to be a marine biologist.
- When you see horseshoe crabs on the beach, they are at least 8-10 years old because that is when they start to breed.This hyperlink shows a horseshoe crab molting. http://youtu.be/Daz8nkh-pWM
- Native americans ate the horseshoe crab (probably the eggs—like we eat shad roe) and they used their tails as spear points.In the late 1800’s to early 1900’s, horseshoe crabs were used as fertilizer. People pulled their wagons (or later, their trucks) right up onto the beach and loaded in 1,000s of crabs. They were then ground up to use as fertilizer.
- ACTIVITY: What color is our blood? What element helps carry Oxygen in Humans? IronHorseshoe crab blood is blue because it is based on copper.Their blood reacts to gram negative (bad) bacteria so it is used to test vaccines and sterile hospital equipment to make sure they are safe to use.The crabs are bled and then released back into the ocean.Horseshoe crabs do not have arteries and veins like we have. Their blood bathes their tissues directly. Iron oxidized is reddish brown Copper penny experiment
- The demand for horseshoe crabs peaked in the late 1990s. The population plummeted. After that the breeding ground states got together to regulate the fishing industry. That is why we have to have a license to raise horseshoe crabs.
- Horseshoe crabs are now primarily used for bait. They are cut in half and used to fish for conch and eel.
- Many shorebirds are dependent on horseshoe crab eggs. The Red Knot is special since it migrates from the antarctic to the arctic and back every year to breed.You can see that one of the longest legs of its trip is from South America to our area. When it gets here, it is starving. It depends upon the nutritious horseshoe crab eggs so it can gain weight for the rest of its trip and for the breeding season.
- It takes 10 years for horseshoe crabs to get big enough to breed. So, if we started managing horseshoe crabs in 2000, when would we know whether the regulations are strict enough? (2010)
- Horseshoe crabs are tagged so we can study them. (Like birds are banded). The ones who have donated blood are tagged too.