Snow crabs are crustaceans found in cold, deep waters. Understanding their physical attributes helps in identification. This article explores the visual characteristics that make them distinct.
Key Physical Characteristics
Snow crabs have a small, round, flat carapace, which is their protective outer shell. Male carapaces typically measure 9.4 to 16.5 centimeters (3.7 to 6.5 inches) wide. This hard, rounded shell can appear iridescent, subtly shifting colors, and provides robust protection.
Shell coloration varies from light red to brown on its upper surface, transitioning to white or yellowish underneath. Some individuals may also exhibit a reddish-orange hue. They have ten limbs: eight long, slender walking legs and two claws. These legs are notably long, often extending up to almost one meter in larger males.
Snow crab claws, or chelipeds, are small relative to their long legs and body size; females typically have smaller claws than males. These claws are usually of equal size, serving functions such as catching food and defending against predators. The crab’s eyes are green or greenish-blue and are located on short, movable stalks that can retract for protection. They also possess two pairs of antennae, with the longer pair aiding in navigation and tactile sensing in their underwater environment.
Distinguishing Features
The snow crab’s flat, rounded carapace distinguishes it from other crab species with spikier or more rugged shells. This relatively smooth, hard shell contrasts with the thick, spiky shells seen on crabs like the Alaskan king crab.
A prominent feature of the snow crab is its exceptionally long and slender legs. These elongated limbs allow for efficient movement across the seafloor. This leg-to-body ratio sets them apart from many other larger crab species, which often have shorter, thicker legs.
Their claws are notably smaller compared to their extensive leg span and body, especially when contrasted with other large crab species such as king crabs, known for their substantial, often unevenly sized, claws. Snow crabs, however, possess two claws that are generally of similar size. While their carapaces have some bodily projections or tubercles, these are moderately enclosed and typically do not present as prominent, sharp spines.
A clear distinguishing feature between male and female snow crabs is their size and abdominal flap shape. Males are considerably larger than females, with carapaces reaching up to 150 millimeters in width, while females rarely exceed 95 millimeters. The male’s abdominal flap is triangular, whereas the female’s is broadly rounded, an adaptation for carrying eggs.
Appearance Changes Over Life Stages
Snow crabs undergo significant changes in appearance throughout their life cycle, primarily through molting. As they grow, they shed their hard outer exoskeleton, which is replaced by a new, larger one. Immediately after molting, the new shell is soft and pliable, making them vulnerable until it hardens over several days to weeks.
The color of a snow crab also varies with its age and molting cycle. Newly molted crabs may appear paler or grayish, gradually regaining more intense coloration as their shell hardens. Older crabs tend to have duller coloration, sometimes shifting to an olive hue with a yellowish underbelly. The color of snow crabs also dramatically transforms upon cooking, changing from natural brown, olive-green, or grayish tones to a bright orangey-red due to heat-induced pigment release.
Size is another aspect of their appearance that changes considerably with age and sex. Males grow larger with successive molts until a terminal molt, becoming significantly bigger than females, who cease growth after their final molt at sexual maturity.