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:
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.
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.
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.