Other Parts

Interior parts of animals are somethings that may be forgotten about.  People go through biology classes to see the interiors, yet do we really think about them?

Do we really realize that all animals have similar organs to ourselves?  Do we stop to think about that?

During my last several posts about horseshoe crabs, I made a list of the body parts I haven’t talked about and usually don’t.

They have: a prosoma (top part), opisthosoma (abdomen), carapace (covering), hinge, chelicera, gnathobase, chilarium, genital operculum, gill opercula, gills, anus, cardiac, extracardiac, and subopthalmic. And I may be missing one or two.

Horseshoe crabs breathe through their gills like fish do yet their gills are on the underside of their bodies.  One can only see them when you pick one up and turn it over. They looked like layered fans.  Their gills allow them to breathe, unlike fish, both in water and on land.

And yes, they have a cardiac system to move that blue blood around.  (See earlier post). One of the main criticisms of their bleeding by pharmaceutical companies is that they insert the needles near the hinge on the horseshoe crab which is also right where their main cardiac is located.  This would be like having a large needle jammed in your neck or chest and your blood sucked out.  We don’t know for sure if they feel pain but they must if they have a brain and neurological system.






CaCo3 + chitin help make up the horseshoe crab’s shell.

(See earlier post for information on chitin.)

People complain that it is tough and hard if they step on one.  These two elements are the reason why.

One question I always ask the students who come is: what are your bones made out of? The sad fact is that the majority do not know.  They  know about the TV commercials telling them to drink milk for strong bones but they don’t know WHAT makes their bones strong.

Calcium is the link between all living creatures that have bones and shells.  Calcium is the fifth most abundant element on earth and has many variations (I’m not getting into more than basic chemistry here).  One of the variations that link us to the horseshoe crabs and all of the other shelled animals like oysters and lobsters is CaCO3, or calcium carbonate.

Calcium carbonate is a calcium compound.  We use it all the time and use products that contain it all the time like toothpaste, vitamins, almond milk, as a calcium supplement, and when we eat dark green vegetables like kale.

Calcium carbonate may have the ability to neutralize acid rain in river water and river ecosystems even though it is not soluble, or dissolves, in water.

CaCO3 is the reason we have fossils of horseshoe crabs going back 450 million years.  It is also the reason their shells are so strong and tough.  It is their home, their refuge, their protection.  CaCO3 is the reason they can travel hundreds of miles through the water and then make it to the shores to lay their eggs.

Calcium carbonate is the reason we get to see them now.


The eyes (and telson) have it…..

People are terrified of the horseshoe crab’s telson, or tail.  My reaction is: really? The tail is used to help the horseshoe crab get around in the water, like a rudder on a boat, and they also use it to flip themselves over in the water should they be turned over.  However, it is very difficult for the horseshoe crab to do this on land.  Most of the time they need help, human help, to flip over or risk being eaten by birds and other wildlife.

Another interesting fact I recently learned about the horseshoe crab’s tail: there are photoreceptors on the tail.

What is a photoreceptor?  A photoreceptor is basically a cell that responds to light.

Horseshoe crabs also have 9 eyes and their vision, as we understand it, is very poor. However, they use their eyes and the photoreceptors to navigate their environment.

This gives new meaning to the expression “eyes behind your head”.