Nutrition for the P. camtschatica, like in habitats, depends on what life stage the crab is in. Red king crab larvae are planktivores, consuming phytoplankton and zooplankton. As said before, the abundance of these in the larvae’s environment determines their survival.1
Small crabs start becoming predators like the adult forms, feeding on kelp, sea stars, clams, muscles, nudibranch eggs, barnacles, and molted king crab exuviae (the molted carapace).
The adult red king crabs are more active predators, migrating to regions with higher supplies of food.2 They are able to migrate around now because pods are now less necessary, adults are less vulnerable, becoming more solitary because of their carapace and size. They hunt at night and are generalized as carnivores, even though they may have zooplankton time to time. Adults consume fish, mollusks, aquatic marine worms, aquatic crustaceans, echinoderms, sponges, barnacles, brittle stars, sand dollars, and sea urchins.3 Picture on right of an adult red king crab.
The red king crab eats its food by capturing they prey by its claws, crushing the organism with its right claw and manipulating it with its left. The king crab then chews and shreds the food by its mouthparts, the mandibles (crush food), maxillae (move food closer to mouth), and maxillipeds, enabling the crab to consume a variety of different organisms. They also have a complete digestive system, the path consisting of mainly a mouth, digestive glands, which secrete enzymes to aid digestion, and an anus.
Crabs have an open circulatory system, consisting of a pumping heart, vessles, and a hemocoel. Hemolymph is pumped out of the heart, past the gills, bringing oxygen to the hemocoel, the space between the organs.4