Square crabs are creatures that make hard, sharp tools and weapons for themselves or for sale to others. They do this by chewing up polyp animal flesh into a form of cement that they then form into molds with their blunt claws. Once the molds harden, the crabs fill them with a secretion that later becomes harder than any shell or bone in the reef. Even the molds themselves are so hard that they must be broken open by previously existing tools. Once open, the crabs pull out the new tools. The tool they use the most is the one they use for harvesting weeds to eat.
In the diagram of the square crab, we see a rather typical false crustacean body plan. For clarity, muscles, digestive tracts, blood vessels, and some bones have been removed. Each of the four heads contains a brain attached to a nerve cord running under each backbone.
A) This is the primary gill battery. Smaller respiratory surfaces can be found throughout the body.
B) All false crustaceans have a tough outer skin rather than a true exoskeleton as found in Earth’s crustaceans.
C) This is the internal skeleton, which provides support and attachment points for the muscles.
D) This is the heart. Animals of Ectora have cells that are sensitive to changes in blood pressure. To maintain constant pressure, blood is divided into three or more parallel tubes that beat out of step with one another before being recombined at the other end.
E) This is the hemoacidostat. It maintains a constant blood PH.
F) This is the hemobarostat. When blood pressure rises, it allows excess blood through a valve into a storage bag. When blood pressure falls, it lets it out.
G) This is the molding gland. Square crabs are capable of using casting molds to make tools.
H) This is the gonopore. It allows the passage of gametes in and out of the gonads.
I) This is a gonad. False crustaceans tend to keep their gonads in their legs. During mating, square crabs will line up their gonopores and the male will release 6-celled gametes into the female’s legs. A few days after fertilization, the free-swimming larvae will exit from the female’s gonopore. In other species, such as reefbuilder crabs, the young will then swim their way to the female’s pouch for protection.
J) This organ acts as both pancreas and liver.
K) These are the kidneys.
Written by Daniel Noe, WayOutLife.com