Crabs come in a variety of colors before being cooked. The natural shell color of crabs depends on their habitat and species. While cooked crabs turn bright red, their raw shell color can range from green, blue, orange, yellow, white, brown and more. Understanding the pre-cooking colors of popular edible crab species can help identify them.
Blue Crabs
The blue crab, or Callinectes sapidus, is a common edible crab species found along the Atlantic and Gulf coasts of the United States. As their name suggests, blue crabs have a blueish shell color prior to cooking. More specifically, their shells often appear a dark mossy green on top with hints of light blue on the bottom and legs. The tips of their pincers also tend to be bright blue.
Blue crab shells turn a vivid orange-red when cooked. Their unique pre-cooking shell color comes from pigments in their diet including algae and mollusks. The rich aquatic vegetation of their estuarine habitats lend to their distinctive green-blue hue.
Dungeness Crabs
Dungeness crabs, or Metacarcinus magister, inhabit the west coast of North America. Ranging from California to Alaska, they thrive in the cold Pacific waters. Dungeness crabs shells are generally an olive to purple-brown color prior to cooking with a lighter beige underside. Their legs may have white banding as well.
The purple-brown hue serves as camouflage in their rocky ocean floor and kelp forest habitats. When cooked, they turn the familiar bright orange-red shade. Their unique pre-cooking coloration helps distinguish Dungeness crabs from other west coast crab varieties like red rock crabs which are brownish-red before cooking as well.
King Crabs
King crabs live in cold, deep waters off Alaska and Northern Russia. There are several species of king crabs, but most have a brownish shell color ranging from red to purple. For example, the red king crab or Paralithodes camtschaticus has a burgundy hue before cooking. Meanwhile, blue king crabs or Paralithodes platypus aptly have bluish-gray shells.
Once cooked, all king crab species develop the classic red shell. The varying purple, blue and brown raw colors help camouflage the crabs against predators and rocky ocean substrates while also denoting separate species. King crabs get their pre-cook colors from pigments in their diet of fish, worms and mollusks.
Snow Crabs
Despite their name, snow crabs, or Chionoecetes opilio, are not white in color. Rather, they have shells that appear orange to reddish-brown prior to cooking. In some cases, their legs may have white banding or spots, hinting at their name. Snow crabs inhabit icy, cold waters which lend to their coloring for camouflage.
When cooked, snow crabs turn the same bright red as other crab varieties like Dungeness and blue crabs. The orange and red raw color comes from carotenoid pigments obtained through their diet. Darker sediments in their environment also influence their shell hue.
Atlantic Rock Crabs
Rock crabs, or Cancer irroratus, live along the Eastern seaboard of North America down to Florida. Their shells are olive to brown with hints of red, yellow and white prior to cooking. The carapace has rough, craggy textures resembling the rocky ocean habitats where they are found.
Cooking turns rock crabs the standard orangey-red color. Their natural dark brown and olive hues help them blend in among rocks covered in algae and debris on the sea floor. The coloration comes from pigments obtained from their diet of mollusks, plants and smaller crabs.
Spider Crabs
Spider crabs encompass a number of species worldwide, many of which have spiny, spider-like shells. Japanese spider crabs, or Macrocheira kaempferi, are among the largest crab species in the world. Prior to cooking, they have an orangey-red hue with white spotting on their legs. Meanwhile, Atlantic spider crabs, or Libinia emarginata, have tan to brown camouflaging coloration.
With cooking, the orange and brown shells become a bright red. The raw coloring allows the crabs to blend in with substrates like corals and sponges on the sea floor. Unique patterns and textures on their legs and carapace also provide camouflage from predators.
Hermit Crabs
While not true crabs, hermit crabs are popular pets and scavengers in tide pools. Unlike edible crabs, hermit crabs have a soft abdomen they protect by inhabiting abandoned shells. Shell color can vary dramatically based on the species and type of shell inhabited. Some have natural camouflaging shells while pet species may be painted bright colors.
Common hermit crabs like the Ecuadorian or Hawaiian species have brownish legs with orange claw tips. Their striped legs help them hide among rocks and debris. Meanwhile, pet hermit crabs may be painted with bright nail polish or given artifical colored shells. Overall, hermit crab shell color depends on their habitat, diet and type of abandoned shell they reside in.
Fiddler Crabs
Fiddler crabs, or genus Uca, are small semiterrestrial crabs that inhabit intertidal zones worldwide. They have one oversized claw. Before cooking, fiddler crabs shells are often gray, brown, orange, yellow or green depending on environment and diet. These muddy hues help camouflage them in salt marshes and mangroves.
When boiled or steamed, fiddler crab shells turn orangey pink. Species like the red jointed fiddler crab have shells that are already reddish in color before cooking. The natural palette provides excellent camouflage against shoreline sediments, algae and vegetation where they feed.
Mud Crabs
As their name implies, mud crabs, or genus Scylla, live in muddy habitats in tropical regions. There are several species with varying pre-cooking color including brown, green and orange. Green mud crabs, or Scylla serrata, have light green shells with brown spotting. Meanwhile, brown mud crabs are uniform brown or reddish-brown.
Cookied mud crabs adopt the standard bright red hue like other crabs. Their natural coloration mimics the muddy coastal environments where they reside. Brown, green and orange safely camouflage them from both predators and prey. Some species may also bury themselves for protection.
Pea Crabs
Pea crabs, or genus Pinnotheres, are tiny crabs that live as parasites inside mollusks like oysters and mussels. They have circular, pea-sized shells reaching just an inch across. Given their parasitic habitat, their shells often match the color of their hosts.
Oyster crabs have beige, white or light grey shells. Those inhabiting mussels match the dark brown or blue-black shell color. When boiled or steamed, their small shells turn orangey pink similar to edible crab species. Their adaptive coloring provides optimal camouflage inside host organisms.
Porcelain Crabs
Porcelain crabs, or genus Porcellana, have flat, oval shells adapted for gripping onto corals and rocky reef environments. Shell color varies by species ranging from bright orange to mottled brown or green for camouflage. Some like the Mediterranean porcelain crab have dark blue or violet shells.
When cooked, porcelain crab shells turn orange-red. However, they are not eaten as commonly as other crabs. Porcelain crabs rarely leave their anchored reef environments. Their diverse natural coloration allows them to avoid predation and blend in among the corals and anemones where they form commensal relationships.
Conclusion
Crabs come in a wide array of shell colors before cooking. While they all turn a uniform bright red when boiled or steamed, their raw coloration depends on habitat, diet and need for camouflage. Coastal species like blue, Dungeness and rock crabs have green, brown and orange hues matching their environments. Meanwhile, reef-dwelling porcelain and spider crabs better blend in with bright orange, white, blue or purple shells.
Understanding the natural palette of crabs helps identify species and habitats. It also reveals nature’s elegant designs for disguise and survival. So while cooked crabs all look alike, in their raw form, they encompass quite an array of colors.
| Crab Species | Raw Shell Color |
|---|---|
| Blue Crab | Greenish-blue |
| Dungeness Crab | Purple-brown |
| King Crab | Red, purple, blue |
| Snow Crab | Orangey-brown |
| Rock Crab | Olive, brown |
| Spider Crab | Orange, brown, white |
| Hermit Crab | Varies by shell |
| Fiddler Crab | Brown, orange, yellow, green |
| Mud Crab | Green, brown, orange |
| Pea Crab | Match host mollusk |
| Porcelain Crab | Orange, brown, blue, purple |
