Wildlife of the Week!

A Puget Sound King Crab with carapace and chelae visible. Note the extensive shell surface.

Wildlife of the Week is back again to highlight an especially exciting creature from the depths! This animal has a tough, intimidating shell and an amazing life history to match. The Puget Sound King Crab (Lopholithodes mandtii), not to be confused with the Alaskan King Crab, is a ferocious invertebrate of the Pacific. Measuring up to 30 cm across and bearing eight legs, the Puget Sound King Crab is an icon of the Salish Sea. Read along below to learn more about this fantastic crab. 

The Puget Sound King Crab is a large and colorful species in the Salish Sea. Its adult carapace (think “top shell covering”) as mentioned, can reach widths of 25-30 cm or more. The exterior of the animal is perhaps the most impressive; with ridges, tubercles, bumps, knobs and spines, the outer surface of this crab helps to aid its survival through protection as well as camouflage. In juveniles, this appearance is even more pronounced. This crab is usually covered in patch-like shades of red, yellow, orange, blue and purple across its shell and legs. Six of the eight walking legs are visible, while two are tucked within the body. Also recognizable are the strong, tough chelae (claws) in front of the body. 

This crab has a fairly well understood range along the West Coast. It can be found from Sitka, Alaska to Monterey California, despite its seemingly exclusive “Puget Sound” namesake. A deep-water dweller, the Puget Sound King Crab can be found as deep as 450 feet! This is typically around subtidal, rocky zones with strong currents. Juveniles may be found in shallow tidal areas, and adults move to shallower depths in order to mate in winter- spring months. 

The Puget Sound King Crab is an impressive predator to say the least. With its strong claws capable of capturing and preparing prey, a variety of creatures can be eaten. These include sea urchins, barnacles, echinoderms (e.g. sea star), and sea anemones. The two claws cooperate together, one does the capturing/subduing while the other prepares the food for consumption. It is certainly clear that you would not want to be in the path of this ferocious crab as a small invertebrate! 

The Puget Sound King Crab has an interesting system of reproduction. When adults move to shallower waters, they do so to find a mate. As crabs, this species molts and sheds their “outer shell” with growth. The female must molt before she is able to mate, whereas this does not apply to males. When her eggs become fertilized, she finds her familiar deep waters again, with eggs in tow. These eggs will finally be released during the next spring. The female will spend about 12-14 days hatching the eggs. 

Males do not follow the same pattern and will remain in shallow waters longer. Once the eggs have been released, they will join “the plankton” for a time in the larval stage (about two months) before settling to grow into adults. 

To elaborate further on the “molting” situation of crabs is to explain a fascinating feature of their evolution. When crabs grow, their softer inner body begins to fill out their hard, non-living exterior shell (which does not grow as the body does). When the crab has completely filled the size that their shell contains them in, it is “shed”. The crab must grow an entirely new, larger shell to continue the process once again. 

Despite being an obvious species in the ecosystem, there exist some unknowns to the Puget Sound King Crab. Estimates of their populations are somewhat unknown, and lifespans are not completely understood. It is believed that the species is not a rare one, but has possibly been reduced in number. 

It is obvious that this species of crab is truly unique and spectacular. To test your knowledge of this crab, try out some trivia below!

  1. True or False? This crab, with its tough shell, is commonly referred to as an “underwater mini tank”. (ANS: True). 
  2. How many eggs can the female bear? (ANS: About 180,000). 
  3. This crab has ____-like teeth on its chelae. (ANS: molar). 

BONUS CHALLENGE: 

The Puget Sound King Crab is similar to another species in shape, which goes by the name of…..? 

Brown box crab. 

OR…

Lopholithodes foraminatus.

Article Authored By: Alexa D., B.Sc./ Five Star Whale Watching. 
To learn more about this crab, visit our References below!

Biodiversity of the Central Coast.

E-Fauna B.C.

Oregon Coast Aquarium.

Understanding Evolution.

Vic High Marine.