Kelp Crab (Pugettia producta)

KINGDOM Animalia
PHYLUM Arthropoda
CLASS Malacostraca
ORDER Decapoda
FAMILY Epialtidae


These crabs are in a large group of crabs called spider crabs. They generally have long legs with relatively small body, usually conspicuously pointed in front. this species is usually dark brown, with a roughly squareish carapace except for the pointed front. Males are a bit larger than females and may be as much as 93 mm (almost 4 inches) across. Younger crabs may be olive-green as well as red or brown.

Kelp crabs, as their name implies, are typically associated with species of kelp, and they are colored much like them. They are also common, especially younger individuals, in the low intertidal in beds of other algae and eelgrass. They are easily found under rocks and other objects at extreme low tides. Handle them carefully; their large chelipeds are good defensive adaptations.

Like the shore crabs, kelp crabs are herbivores most of the time. During the summer they nip off bits of brown algae such as kelp, rockweed, and sargassum, as well as several types of red algae. When the algae die back during winter, they turn to an animal diet, including small mussels and barnacles as well as smaller creatures such as bryozoans and hydroids. An animal that can change its diet seasonally is always at an advantage.

Where sea otters are common, they are significant predators on kelp crabs. These fairly large and not particularly evasive crabs are obviously excellent prey items for a shellfish predator that hangs out in kelp beds.

Females can be seen carrying eggs throughout most of the year. Such females are absent for several summer months, and it is thought they move to deeper water then. A female may lay as many as 84,000 bright orange eggs, which change color to deep red as embryonic development ensues. The eggs take about a month to hatch into tiny zoea larvae.