Crab 101
Species Interactions
About the Author


    The red king crab, Paralithodes camtschatica, has a reddish-brown body and characterized by its fan shaped tail.  To cover the basics, they are bilaterally symmetrical, ectothermic, as well as heterothermic.  For sexual dimorphism, their sexes look very alike, mainly differing in their size, males are usually bigger, and through the different shapes of their abdominal flap.  The average lifespan for the king crab is usually from 15-20 years, yet the longest known wild lifespan can be from 20-30 years.1   

Caleb Parker with an Alaskan King Crab.  -picture taken by Fronty Parker “If bigger is better, then the king crab is the best crab you can buy,” says the Pacific Sea Group.  But this statement is true.  The red king crab is the largest member in its family, the spider crabs, weighing as much as 20 pounds, usually averaging six to eight lbs.2  Also, this remarkably large species can have a carapace up to 11 inches in width and leg span exceeding six feet!3  

    The head and thorax of a crab are fused together.  Even though fused, the crab is still segmented, having 5 sets of legs, the first pair being their claws, or pincers, the next three pairs being walking legs, and the last pair being fairly small, which are tucked up underneath the carapace.The king crab’s number of legs and claws set them apart from other crab species in that most crabs have 4 sets of walking legs, king crabs having 3, and that the king crabs differ in their types of claws.  They have a larger right “killer” claw for crushing and a smaller “feeder” claw on the left for manipulating their food.On the head of the crab, there is a collection of antennae and mouth parts, including the mandibles, maxillae, and maxillipeds.  The king crab’s carapace is heavily calcified and is covered with many sharp spines, their legs also covered in spines, for increased protection.P. camtschatica uses tactile and chemical communication, using both sense of touch and pheromones to interact with each other and their environment.  

            Distinguishing characteristics of the red king crab are more than just size and color.  The red king crab and the blue king crab, its nearest relative, are not so easy to tell apart, making their size and shell color not decisive enough.  The red king crab differs in its skin coating, being a pink color, while the blue king crab is a deeper red.  Also their spine colors differ, the red king crab’s being red and white tipped and the blue king crab being blue and black tipped.The number of spines is also a definite distinguishing trait, red king crabs having 33 spines total on its carapace, 9 in front, 9 on each side, and 6 in the back.8  This picture by Lis Lindal Jørgensen of the red king crab, showing the different areas of its carapace.



They are living, breathing eukaryotic organisms, lacking a cell wall. (Freeman, 2005)



They are classified as protostomes in the subgroup Ecdysozao, having segmentation, also having a jointed exoskeleton like its ancestors, the insects, scorpions, and millipedes. (Freeman, 2005)



They have a shell, a carapace, as well as a short tail. (“Red King Crab: Information from Answers.com” Answers.com)



They have 5 pairs of walking legs as well as a cephalothorax. (“Red King Crab: Information from Answers.com” Answers.com)



They have a reduced fifth walking leg and are king crabs found in the cold seas. (“Red King Crab: Information from Answers.com” Answers.com)



They are edible, deep sea crabs found along the coasts of Japan to Canada.(“Red King Crab: Information from Answers.com” Answers.com)


Paralithodes camtschatica

Are the largest king crab which is a reddish/brown color, having 33 red and white spines and a extensive carapace.(Jørgensen, 2006)













(Ghiselin, 2007)

Phylogenetic Tree Below!


Text Box: Chordata
Text Box: Paralithodes
Text Box: Arthopoda
Text Box: Porifera
Text Box: Cnidarea
Text Box: Ctenophora
Text Box: Platyhelminthes
Text Box: Nematoda
Text Box: Annelida
Text Box: Mollusca
Text Box: Echinodermata
Text Box: Chelicerata
Text Box: Crustacea
Text Box: Uniramia
Text Box: Arachnida
Text Box: Merostomata
Text Box: Araneae
Text Box: Aranae
Text Box: Acarina
Text Box: Scorpionida
Text Box: Chilopoda
Text Box: Insecta
Text Box: Diplopoda
Text Box: Malacostraca
Text Box: Decopoda
Text Box: Brachiopoda
Text Box: Pleocyemata
Text Box: Anomura
Text Box: Paguroidea
Text Box: Coenobitidae


Text Box: Paralithodes
Text Box: Phylogenetic Tree

Text Box: Diogenidae
Text Box: Parguridae
Text Box: Lithodidae
Text Box: Parapaguridaesca
Text Box: platypus