''Pugettia producta'', known as the northern kelp crab or shield-backed kelp crab, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Epialtidae Epialtidae is a family of crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden e ...

Description

Its upper

carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...

is typically dark brown, olive, or olive-brown. The underside surface tends to be more vibrant having colors such as red, yellow, or orange. Younger crabs may be lighter olive-brown or reddish-brown. The carapace is a badge-like shape similar to a police officer's badge or shield; hence the secondary name shield-backed crab. Its carapace is curved and smooth, with a slick texture. The front of the crab has a protrusion called a

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit ** podium * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ...

, extending the carapace and is used in feeding. They have large chelipeds used for defense and feeding. The northern kelp crab is part of the spider crab family and exhibits the long many jointed hairless legs associated with the family. Their long legs and shield-like carapace are key identifying factors.

Distribution

It is found along the Pacific Coast of North America from southern

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

to northern

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

Sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

Male crabs tend to be slightly larger than female crabs at about across the carapace. Females tend to be . Female crabs exhibit a broader back and smaller chelipeds than males.

Behavior

Northern kelp crabs are known for their association with kelp and their similar coloration. Their long many-jointed legs have evolved to help them climb bull kelp and also provide help climbing man-made pilings. These crabs are also common in lower

intertidal zone The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various ...

s in beds of

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

eelgrass Eelgrass is a common name for several plants and may refer to: * '' Zostera'', marine eelgrass * '' Vallisneria'', freshwater eelgrass See also *'' Potamogeton compressus'', known as eel-grass pondweed {{Short pages monitor