ON GUARD THE THIGH MOUTH!

When the weather gets cold and you can feel your sinuses begin to freeze, you might consider indoor entertainments.  My crew likes to go visit the aquarium and we are blessed to have two within an easy drive of our home town.  A staple at aquariums, seems to be the horseshoe crab.  Horseshoe crabs are a type of arthropod (animal with an exoskeleton and jointed appendages).  The fossil record indicates these animals have not changed much in millions of years and are therefore considered living fossils.  Their body is comprised of an anterior prosoma and the back portion is referred to an opisthosoma (aka “abdomen”).  The opisthosoma ends in a long spine.  It would be fun to imagine horseshoe crabs using their spines (called “telsons”) as weapons.  Imagine two horseshoe crabs preparing for a telson duel … “On guard!” one says in a bad French accent “You dare to enter my territory and mate with my female! You must pay!” and the fight begins!  The telson is not used for defense.  It is used to right themselves if them get flipped on their backs.  (I know the duel and bad accents were more fun!).  The real use of the telson, rather than for dueling, is why aquariums allow kids to touch these critters.  They are frequently found in the “petting zoo” parts of aquariums.

Horseshoe crabs have five pairs of legs used for walking and a pair of chelicerae.  Chelicerae are pincher-like structures.  Spiders and mites also have chelicerae so these all get classified as “Chelicerates”.  The walking legs are my favorite part of a horseshoe crab.  The first four pairs of walking legs have a bunch of spines at the base of the leg.  These spines are used to tear up the food and then move the food along to the mouth.  Because these modified legs act like teeth, the horseshoe crabs were classified as “Merostomata” which literally means “thigh mouth”.  This makes me giggle every time.  Regrettably, higher minded zoologists than I have suggested these be renamed to “Xiphosura” which refers to the Greek “xiphos” for sword.  Well, I suppose that works too.