Archive for the ‘Horseshoe Crab Lifecycle’ Category

Horseshoe Crab Reproduction – a slim chance of survival

Thursday, May 21st, 2009

Horseshoe crabs have a unique reproductive strategy.

The female horseshoe crab, with a male horseshoe crab in tow will come up to the shore line and lay up to 20,000 eggs in a number of shallow nests that she makes along the beach.

After laying the eggs she pulls the male over the nest when he then fertilizes the eggs.

It’s a good thing that she lays so many eggs because they then leave the nest unattended and the eggs are then open for predators to eat, mainly shorebirds.

Typically it is estimated that only 1/10 of 1 percent of the eggs will end up surviving to adult hood. With this dismal chance of survival it’s a good strategy that they lay so many eggs.

In all but the warmer climates horseshoe crabs will only mate once a year. This being in late spring to early summer.

Down here in Florida they mate pretty much year round except in mid winter when they bury themselves in the sand for a couple of months till things warm up a bit.

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Odd looking Horseshoe Crab

Sunday, May 17th, 2009

I received this picture along with this email a couple of weeks ago. Take a look….

Photo of a horseshoe crab molting

Photo of a horseshoe crab molting

This is the letter that she sent.

“We found a horseshoe crab on the beach (Buckroe Beach in VA) While
observing the crab on the beach it looked very odd. So I took a couple of pictures.


After looking at a number of websites I still cant understand what I am looking at as all the pics on the sites don’t show anything like what I see.

Where book gills should be there are these organ looking things. (pic 2/ 085JPG) Now do you think something was ripped off of the crab or.. well what is it I am seeing?

My children and I are very interested to know.”

This is horseshoe crab that is about ready to molt. Horseshoe crabs molt their shells up to 18 times during their life. This is just a part of the growing process because the shell does not grow.

The horseshoe crab inflates itself with water (that’s why it looks so
strange) and this helps it break free of it’s shell, this is called molting.
Shorting after leaving the shell (molt) it will form a new shell that it will
keep until it’s ready to molt again.

With a horseshoe crab at the age of the one in the picture, that won’t be for probably another year or so.

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