Humans
Quite obviously crayfish, humans, and many other animals have apendages. Snails, however do not.
Humans
the natural predator to the crayfish is the common seagull
Exoskeleton: Crayfish have a hard shell, and no bones. That makes crayfish invertebrates (no spine). Gills: Crayfish respire underwater through gills, where humans use lungs. The circulatory system is the second one, the reason for this being that crayfish have no blood vessels (and humans obviously do).
humans- crayfish-
The structure in humans that the digestive glands are comparable with crayfish are the glands that are found in the mouth and the stomach. These glands will secrete salivary amylase and HCI respectively to aid digestion in humans.
Nephridiopores in crayfish are part of their excretory system (for removing nitrogenous waste); crayfish propel water from the rear to the front and out the nephridiopores. It is analogous to how humans have to expend their liquid waste.
Not only do they eat crayfish, it is a common food source for larger browns.
NOTHING
A crayfish's heart pumps hemolymph (the crayfish equivalent of blood) throughout its body, distributing oxygen and nutrients to its tissues and organs. The heart is a tubular structure located on the dorsal side of the crayfish, above the stomach.
Humans, bass, otters, mink and raccoons.