I’m Feeling a Bit Crabby

While in the Florida Keys last week I saw a ton of crabs, both true crabs and other crab-like organisms.  As a Michigander living far from the ocean, these were the first crabs I had seen in the wild.  I admit I know little of their taxonomy, but I’m going to stumble through a bit of it as I go through the photos I took.

First, there are the true crabs (Arthropoda:  Crustacea:  Malacostraca:  Decapoda:  Brachyura).  This infraorder of crustaceans includes nearly 7,000 known species.  Here are but three:

True crab (Arthropoda: Crustacea: Malacostraca: Decapoda: Brachyura) photographed 04/09/2012 on Grassy Key, Florida.

True crab (Arthropoda: Crustacea: Malacostraca: Decapoda: Brachyura) photographed 04/09/2012 on Grassy Key, Florida.

True crab (Arthropoda: Crustacea: Malacostraca: Decapoda: Brachyura) photographed 04/09/2012 on Grassy Key, Florida.

I have no idea what the first two crabs were, and for all I know they’re just two color variants of the same species.  I found them crawling about the muck on a tidal flat on Grassy Key.  The third crab was in the same area but submerged.  I suspect it was a juvenile Atlantic blue crab (Callinectes sapidus, Portunidae).  

Far more common were hermit crabs (Arthropoda:  Crustacea:  Malacostraca:  Decapoda:  Anomura:  Paguroidea).  Despite the common name, these are not true crabs but are related decapod crustaceans.  I found scores of these on the tidal flats of Long Key and Grassy Key, each living within the shell of a gastropod.  They were so common that any shell of any size that I found had a hermit crab living inside.

Hermit crab (Arthropoda: Crustacea: Malacostraca: Decapoda: Anomura: Paguroidea) photographed 04/09/2012 on Long Key, Florida.

Hermit crab (Arthropoda: Crustacea: Malacostraca: Decapoda: Anomura: Paguroidea) photographed 04/09/2012 on Long Key, Florida.

Hermit crab (Arthropoda: Crustacea: Malacostraca: Decapoda: Anomura: Paguroidea) photographed 04/09/2012 on Long Key, Florida.

On Long Key I also found some exoskeletons of dead horseshoe crabs (Arthropoda:  Chelicerata:  Merostomata:  Xiphosurida:  Limulidae).  These “crabs” are even further from true crabs than hermit crabs.  Horseshoe crabs aren’t even crustaceans…they’re in the same subphylum as spiders and scorpions.

Dead horseshoe crab (Arthropoda: Chelicerata: Merostomata: Xiphosurida: Limulidae) photographed 04/09/2012 on Long Key, Florida.

To Floridians these awesome little critters are probably no big deal.  For a midwesterner like me, however, I thought it was pretty remarkable to find so many of these diverse and fascinating creatures in such a short time.

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About Jeremy Sell

Science and nature nerd.
This entry was posted in Invertebrate Zoology and tagged , , , , , . Bookmark the permalink.

One Response to I’m Feeling a Bit Crabby

  1. Nice photos. . .As you probably know, horseshoe crabs’ eggs are an important food source for migrating shorebirds in the mid-Atlantic states, but their numbers are declining. I used to see them a lot at Rehobeth Beach, DE, when I was a kid. They are mysterious and beautiful creatures.

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