Crustaceans

Crustaceans form a very large group of arthropods (meaning jointed-leg) that are a widespread group of animals with the greatest number of species.  Marine arthropods include barnacles, isopods, shrimps, and crabs.  All members of this group have an exoskeleton (a skeleton that covers their body like armor).

 

     
 Red Rock Crab (Cancer productus)  
 Red Rock Crab

Description: A large crab found locally in shallow water under seaweed and rocks. Found on sandy, silty and rocky beaches. Carapace is dark red and fan shaped; heavy claws tipped black. Hard carapace protects the head and thorax while locomotion is accomplished by four pairs of walking legs and one pair of pinchers. Sheds shell and creates new larger one as the animal grows. Up to 7 in (18 cm) across the carapace.

 
 Food: Opportunistic consumer of a wide variety of small creatures including snails, barnacles, small crabs, and dead fish.  
 Reproduction: Females produce eggs. Planktonic larvae develop through different life stages in the water column.  
 Fun Facts: Claws are strong enough to crack open barnacles and snails. Juveniles often are alternately striped white and red.  
   

 

Dungeness Crab

 

(Cancer magister)

 
 Dungeness Crab Description: A large crab found locally in eelgrass beds, but mostly subtidal in distribution. Shell grayish-brown (with hints of purple at times), legs tan, claws white. Hard carapace protects the head and thorax while locomotion is accomplished by four pairs of walking legs and one pair of pinchers. Sheds shell and creates new larger one as the animal grows. Can burrow backwards up to its eyes. Up to 9 in (23 cm) across the carapace.  
 Food: Eats small clams.  
 Reproduction: Females produce eggs. Planktonic larvae develop through different life stages in the water column.  
 Fun Facts: An important commercial species, its collecting is strictly regulated. Known to live up to six years.  
   

 

Kelp Crab

 

(Pugettia producta)

 
 Kelp Crab Description: Called a "spider" crab due to its long, thin legs. The carapace is shaped like a shield and is usually greenish-brown or reddish. Found among seaweeds on rocky shores, around pilings and sometimes in eelgrass beds. Hard carapace protects the head and thorax while locomotion is accomplished by four pairs of walking legs and one pair of pinchers. Sheds shell and creates new larger one as the animal grows. Up to 3.5 in (9 cm) across carapace.  
 Food: Primarily eats kelp and brown algae, but will feed on a wide variety of small creatures if its preferred seaweeds are unavailable.  
 Reproduction: Females produce eggs. Planktonic larvae develop through different life stages in the water column.  
 Fun Facts: In the autumn, adults migrate to deeper water where mating takes place. By December, mating is over and they return again to shallower waters.  
   

 

Decorator Crab

 

(Oregonia gracilis)

 
 Decorator Crab Description: Another "spider" crab, with long slender legs. Found among seaweeds in the intertidal zone. Hard carapace protects the head and thorax while locomotion is accomplished by four pairs of walking legs and one pair of pinchers. Sheds shell and creates new larger one as the animal grows. Up to 1.5 in (4 cm) across carapace.  
 Food: Primarily eats kelp and brown algae, but will feed on a wide variety of small creatures if its preferred seaweeds are unavailable.  
 Reproduction: Females produce eggs. Planktonic larvae develop through different life stages in the water column.  
 Fun Facts: This crab known for its elaborate camouflage comprised of living seaweeds, sponges and bryozoans delicately fastened to the shell with a glue-like secretion from its mouth.  
   

 

Helmet Crab

 

(Telmessus cheiragonus)

 
 Helmet Crab Description: A "hairy" crab found in eelgrass beds or among seaweeds. Round carapace with six 'teeth' on each side. Yellowish-green locally. Hard carapace protects the head and thorax while locomotion is accomplished by four pairs of walking legs and one pair of pinchers. Sheds shell and creates new larger one as the animal grows. Buries itself in sediment. Up to 4 in (10 cm) across carapace.  
 Food: Feeds on eelgrass, algae, snails, small clams, and worms.  
 Reproduction: Breeds in the early spring. Females produce eggs. Planktonic larvae develop through different life stages in the water column.  
 Fun Facts: This species of crab also lives in Japan.  
   

 

Purple Shore Crab

 

(Hemigrapsus nudus)

 
 Purple Shore Crab Description: Adult is dark reddish-purple, with pink to orange claws covered by dark red spots. Hard carapace protects the head and thorax while locomotion is accomplished by four pairs of walking legs and one pair of pinchers. Sheds shell and creates new larger one as the animal grows. Common in the rocky intertidal habitats under rocks. Carapace up to 2 in (5 cm).  
 Food: Feeds on sea lettuce and other green algae, as well as barnacles.  
 Reproduction: Females produce eggs. Planktonic larvae develop through different life stages in the water column.  
 Fun Facts: This crab feeds mainly at night.  
   

 

Green Shore Crab

 

(Hemigrapsus oregonensis)

 
 Green Shore Crab Description: Green or grayish-green. Can be white or mottled when young. Hard carapace protects the head and thorax while locomotion is accomplished by four pairs of walking legs and one pair of pinchers. Legs have fine hairs. Sheds shell and creates new larger one as the animal grows. Found in sheltered areas under rocks, in eelgrass beds and in sandy intertidal areas. Up to 1.75 in (4 cm) across the carapace.  
 Food: Feeds on sea lettuce and other green algae. Also a scavenger of small organisms, and may even filter water for detritus.  
 Reproduction: Females produce eggs. Planktonic larvae develop through different life stages in the water column.  
 Fun Facts: A type of red ribbon worm is a predator of the eggs of this crab.  
   

 

Pea Crab

 

(Pinnixa spp.)

 
 Pea Crab Description: White with dark markings. Hard carapace protects the head and thorax while locomotion is accomplished by four pairs of walking legs and one pair of pinchers. Sheds shell and creates new larger one as the animal grows. Found mainly in the mantle (inside the shell) of the horse clam. These crabs live in pairs with the female being much larger than the male. Carapace up to 1 in (2.5 cm).  
 Food: The female feeds on plankton brought in with the currents produced by the clam. She will also eat strings of mucus. It is unclear what the male eats.  
 Reproduction: Females produce eggs. Planktonic larvae develop through different life stages in the water column. Young pea crabs may be found together with adults in the clam, but only one adult pair will be found.  
 Fun Facts: The young of this species are also found inside other smaller clams, and can apparently migrate as they mature, into horse clams.  
   

 

Hairy Hermit Crab

 

(Pagurus hirsutiusculus)

 
 Hermit Crab Description: Narrow white band on lower part of each walking leg. Brownish antenna banded white. Much of this crab is covered in hair. These crabs' soft abdomens taper and curl to fit into an empty snail shell, then move into progressively larger shells as they mature. Found in tidepools in the rocky intertidal zone. Carapace to .75 in (2 cm).  
 Food: Feeds on algae, detritus and scavenges bits of other creatures.  
 Reproduction: Females produce eggs. Planktonic larvae develop through different life stages in the water column.  
 Fun Facts: This hermit crab has distinct preferences for its home. Favorite local snail shells include the striped dogwinkle.  
   

 

Acorn Barnacle

 

(Balanus glandula)

 
 acorn barnaclec Description: A relative of shrimp, barnacles drift when in their planktonic larval form until they cement their heads to a hard surface such as a rock, shell or bit of wood. They then metamorphose into the adult form with six outer and four inner protective plates. Our most common barnacle, growing to .75 in (2 cm) diameter. When crowded, grow into tall hexagonal columns.  
 Food: Modified legs sweep the current catching drifting detritus and plankton.  

 Reproduction: Barnacles reach sexual maturity at about 80 days of age. Males may become females, and vice versa, at any time. To reproduce, the male must find a female within reach of his reproductive organ, which can reach up to 20 times his body length. Reproduces two to six times a year.

 
 Fun Facts: The cement used by barnacles to attach themselves to hard surfaces has been studied and reproduced in a class of glues that include dental adhesive and Super-Glue. Some individuals can live for 15 years.  
   

 

Giant Acorn Barnacle

 

(Balanus nubilis)

 
 Giant Acorn Barnacle Description: A relative of shrimp, barnacles drift when in their planktonic larval form until they cement their heads to a hard surface such as a rock, shell or bit of wood. They then metamorphose into the adult form with six outer and four inner protective plates. One of the world's largest barnacles, growing to 2.75 in (7 cm) in diameter and 5 in (13 cm) high.  
 Food: Modified legs sweep the current catching drifting detritus and plankton.  
 Reproduction: Barnacles reach sexual maturity at about 80 days of age. Males may become females, and vice versa, at any time. To reproduce, the male must find a female within reach of his reproductive organ, which can reach up to 20 times his body length. Reproduces two to six times a year.  
 Fun Facts: Feeding appendages can reach out 2 in (5 cm) or more to feed. Some individuals can live for over 25 years! These barnacles were traditionally eaten by Native and First Nation peoples. They would roast them in embers before eating.  
   
   

 Thatched Barnacle

(Semibalanus cariosus)

 

 thatched barnacle

 Description: White in color while older or crowded specimens may be grayish. Spines covering walls give it a 'thatched' look. To 1.5 in (4 cm) in diameter, 2 in (6 cm) high. Attaches to rock in mid-intertidal zone. Ochre sea star is main predator.  
  Food: Modified legs sweep the current catching drifting detritus and plankton.  
  Reproduction: Females are known to brood their young over the winter months and release them when spring arrives.  
  Fun Facts: Individuals have been known to live for 15 years.  
   

 

Coon Stripe Shrimp

 

(Pandalus danae)

 
 coon shrimp Description: Also known as dock shrimp, these translucent shrimp can reach 5.5 in (14 cm) in length. The body shows reddish-brown irregular stripes, with thin white lines and many small blue spots. Found on pilings and floats, intertidally to over 600 ft (183 m) in depth. Shrimp have walking legs as well as appendages called swimmerettes that are used for swimming and for attachment of eggs.  
  Food: Feeds on zooplankton and small crustaceans.  
  Reproduction: Eggs brood while attached to swimmerettes on females.  
  Fun Facts: This species is quite important commercially.  
   
   

 Spot Shrimp

(Pandalus platyceros) 

 
 spot shrimp Description: Largest shrimp in Puget Sound. Can change colors from brown, red or green to match background colors, and is distinguished by four white spots on its body.  May reach 10 in (25 cm) in total length.  Seeks protection in deep water and rocky outcroppings.  
  Food: Wide variety of small crustaceans, worms, clams, and plankton.  
  Reproduction: Eggs brood while attached to swimmerettes on females.  
  Fun Facts: This shrimp is capable of moving lightning-fast, which aids it greatly in avoiding predators.  
   

 

Rockweed Isopod

 

(Idotea wosnesesskii)

 
 Isopod Description: A relative of the pill bugs found terrestrially (on land), this marine isopod feeds on algal detritus. It is olive green and grows to about 1.5 in (4 cm) in length. A close relative, the eelgrass isopod looks very similar and is found in eelgrass beds clinging to the grass blades.  
 Food: Eats algae and algal detritus.  
 Reproduction: Female lays eggs.  
 Fun Facts: Like the pill bug in one's garden, this isopod can curl up when threatened.