Crabs come in a stunning array of colors and patterns that can dazzle the eyes. From fiery reds to cool blues these ten-legged crustaceans display nature’s palette. But what determines the specific colors that individual crabs exhibit? In this article we’ll explore the pigments, biology and behaviors behind the color diversity of these captivating creatures.
Camouflage Drives Crab Colors
One of the primary functions of coloration in crabs is camouflage. Blending into their surroundings helps crabs evade predators and sneak up on prey undetected. Their ability to match diverse marine backdrops aids their survival. Here are some examples:
- Rock crabs often sport reddish-brown hues to mimic coral and the ocean floor.
- Shore crabs blend with intertidal rocks in mottled greens.
- Ghost crabs burrow into sandy beaches, concealed by their white-hued bodies.
Crabs have specialized chromatophore cells that can expand or contract pigments to alter shades for camouflage. Diet molting and age can also impact the tones crabs display. But camouflage is key, dictating much of their diverse palette.
Species-Specific Pigments
While camouflage is a major driver, species inherent pigments also contribute to crab coloration. Here are some common species and associated hues
- Green shore crabs – Shades of green with mottling
- Dungeness crabs – Reddish-brown shells with black-tipped claws
- Spider crabs – Variable colors including brown, orange and red
- Blue crabs – Blueish-green shells with brown and purple mottling
- Hermit crabs – Translucent exteriors when not in shells
These species contain unique color signatures that influence their palette, despite camouflage needs. For example, blue crabs always maintain some blue hues. And dungeness crabs keep their bold red claws.
Habitat Adaptations
In addition to innate species coloration, habitat significantly impacts crab pigments. Shore crabs match the brown and green algae covered rocks where they live. Meanwhile, coral reef crabs mirror the vibrant pinks and oranges of their surroundings.
Diet affects color too. Crabs consuming more red algae accumulate carotenoids and become redder. Molting enables adaptation to new habitat colors as well. Crabs continually evolve to blend into their local environment through chromatophore adjustments.
Life Stage Shifts
Younger crabs often exhibit much more vivid and striking colors than adults of the same species. For instance, juvenile spider crabs can be electric blue and orange. Their vibrant tones help camouflage with coral and avoid predator notice.
As crabs mature, their shells tend to darken and fade. Pigments blend together. These muted adult hues enable improved camouflage. Reproduction impacts color too, with male fiddler crabs becoming neon red/yellow during mating periods. Their life stage plays a key role in determining crab palette.
Unique Crab Colors
Beyond traditional sand-hued light crabs and coral-resembling red crabs, some species display more unusual colors:
- Blackback land crabs – Dark brown/black shells
- Ghost crabs – White or light shells matching sandy beaches
- Glass crabs – Nearly transparent exteriors reflecting habitat
- Rainbow crabs – Bright red legs and stunning blue shells
These unique palettes expand the diversity of hues and patterns crabs utilize for camouflage, communication and mating. Though less common, they showcase the range of tones crabs can exhibit.
What Impacts Crab Color Changes?
Crabs periodically molt their exoskeletons, allowing opportunities for color changes. Factors influencing shell color at molting include:
- Age – Recently molted shells appear lighter. Darker pigments accumulate over successive molts.
- Diet – Impacts pigment production.
- Habitat background – New backdrop colors become incorporated.
- Camouflage needs – Tones shift depending on required camouflage.
- Temperature – Can impact pigment production.
- Time since last molt – Shell color can slightly change from molting itself.
While often overlooked, crab coloration provides deep insights into marine biology, evolution and biodiversity. Much remains to be learned about the capabilities and constraints around crab color adaptations. But their beautiful hues clearly serve critical functions, enabling crabs to prosper across the oceans’ endless nooks and crannies.
Purple Rock Crab
- Latin name: Leptograpsus variegatus
- Habitat: Rocky coastal areas of Australia, New Zealand, South America, and some Pacific islands
- Size: Carapace up to about 2″ long
- Diet: Algae, limpets, barnacles, and other plant and animal matter
- Colorful feature: As its name suggests, the purple rock crab has claws and legs that are an intense shade of purple. Individual crabs may have accents of orange or green, too.
These pretty and distinctive-looking crabs are somewhat different from other purple crabs on the list. That’s because rather than being pure purple, they are usually purple with whitish markings. The exact nature of the markings will vary depending on the crab, but many have claws whose purple color fades to whitish toward the points. They also usually have polka-dot-like white spots.
- Latin name: Hepatus epheliticus
- Habitat: Shallow parts of the western Atlantic Ocean (from about the Chesapeake Bay to the Dominican Republic)
- Size: Carapace up to about 3″ wide
- Diet: Various types of detritus on the ocean floor
- Colorful feature: At first glance, the calico crab almost looks like a cartoon. Its shell is usually white or off-white and covered with orange, red, or purple spots. Those spots are outlined in a darker color that gives the calico crab a distinctive and clean-lined look.
The calico crab is a useful part of the ocean’s “garbage disposal,” as it eats decomposing plant and animal matter. It also frequently carries an animal called the “hitchhiking anemone” on its back. This is something that benefits both: the anemone has access to more food as the crab carries it around, and the crab is protected from predators by the anemone’s stinging ability.
4 Crowned Coral Crab
- Latin name: Quadrella coronata
- Habitat: Coral reefs around New Caledonia, Mozambique, Madagascar, and Seychelles
- Size: Carapace up to about 0.5″ wide
- Diet: Various marine animals it finds in coral reefs
- Colorful feature: Not every crowned coral crab is this colorful. But some individuals are bright yellow or even a unique yellow-white pattern like the one in the picture.
This interesting-looking crab isn’t quite as talked about as some of the other crabs on the list. It looks and behaves similarly to guard crabs, and its relatively flattened shell makes it easy for it to hide among coral branches. Notably, most similar species have patterns of red and white as opposed to yellow and white.
HOW TO COLOR CRAB
FAQ
What color is a crab?
Color is variable, and not the best characteristic to identify green crab. Green crab can be green, black, or yellow on top of carapace and have white, yellow, orange, or reddish undersides and leg joints.
Is a crab red or orange?
Alive, red king crab are actually a dark burgundy in color. When they are cooked they turn bright red- with scarlet-red highlights on the top part of the shell, and especially around the toes.
What color are crabs when they are alive?
But when they’re roaming free on the ocean floor, crabs and lobsters are usually brown, muddy green, or dull blue.May 24, 2017
What color is crab when cooked?
Fully cooked stone crabs have shells that are bright red or orange. If yours is green or brown, you can assume it has not been cooked.Aug 26, 2024