Pugettia productanorthern kelp crab

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Geographic Range

Pugettia producta is found within the rocky intertidal shores between Asuncino Point, Baja California all the way up to Alaska (Rudy et al. 1987).

Habitat

Pugettia producta can be found in dense kelp beds, and tide pools covered in surfgrass or algae. They can also descend to the depth of 40 fathoms.

Due to its wide range of locations, the temperature range which Pugettia producta can tolerate is somewhat greater than most marine organisms(Ricketts et al. 1985).

Physical Description

This particular family of crab has a unique, elongated carapace, looking like an upside down shovel with the handle end towards its mouth. It has four pairs of slender walking legs and a pair of modified legs called chelipeds. Their abdomen has seven segments.

The color of the crab is food-dependent, meaning that the color greatly depends on the type of algae they consume in their surrounding environment. This particular adaptation gives P. producta a natural camouflage. Mostly, the color is dark brown or olive green, but sometimes there is a mixture of the two colors. It can also be reddish orange; however, this coloring is usually found on the ventral side.

The carapace is smooth and not as hairy as the other crabs. Even in its own family, Majidae, Pugettia producta's legs appear to be smoother. Rarely do you see much debris attached to the outer surface. Their eyes are relatively close together compared to other species of crabs outside of its family.

The male has relatively larger chelipeds than the female. The males' legs are also shorter than the females' (Rudy et al.1987; Mohler et al.1997).

  • Range mass
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Reproduction

Pugettia producta undergoes a terminal molt upon reaching sexual maturity. Gravid females, June to July, copulate by hard-shelled pairs. Soon, reddish-orange or yellow eggs develop underneath the female's abdomen. It is here that the eggs will stay for several months. Sometimes the eggs will remain for two generations or more before they develop into an adolescent crab (Rudy et al. 1987; Ricketts et al. 1985).

Behavior

Pugettia producta can be found within pools of surfgrass. The surfgrass acts as a shield from the sunlight and predators. If a person were to pull some surfgrass away from the P. producta, then she would see its chelipeds in action, pulling the grass back over itself to keep hidden from the sun.

Many of P. producta's family members fit into a special category called the masking crabs. These particular crabs pick up various items, such as tiny shells, algae, and kelp and hook these organic materials to their hook-like structures on the back on their carapace and legs. This adaptation assists them in their efforts to camouflage themselves from its predators. However, P. producta does not fit into this category, because this larger species is moderately more active. Therefore, it needs to keep a clean carapace for smoother movement throughout the intertidal pools (Ricketts et al. 1985).

Food Habits

Primarily, P. producta is a nocturnal vegetarian. In the low rocky intertidal, the crab can been seen in surfgrass beds eating Nereosystis (bull kelp), Ulva (sea cabbage), and Fucus (rockweed). P. producta will also eat barnacles, mussels, hydroids, and bryozoans when its primary food source, algae, is scarce (Rudy et al. 1987).

Conservation Status

Conservation efforts for P. producta would include making sure that there are plenty of kelp beds around for everyone, including both the farmers and the crabs.

A conservative act that a person can do is to replace the surfgrass he pulls back. After looking throughout a pool that has surfgrass on top, it is critical that one puts it back in place because animals beneath the water need their shade. A person should definitely do this when a P. producta is sited.

Other Comments

Scientists have also used the name Epialtus productus for this species.

The crab's appearance puts it into the family Majidae because it looks more like a spider than a crab. Hence P. producta along with other family members are called spider crabs (Rudy et al. 1987; Ricketts et al.1985).

Contributors

Jamie Aleksa (author), Western Oregon University, Karen Haberman (editor), Western Oregon University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

coastal

the nearshore aquatic habitats near a coast, or shoreline.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

native range

the area in which the animal is naturally found, the region in which it is endemic.

References

Hermann, R. Winter 1999. Oasis in the Open sea. California Wild, 52: 21-27.

Mohler, J., D. Fox, B. Hastie. 1997. Guide to Rocky Intertiadal Habitats. Newport, Oregon: Oregon Deparment of Fish and Wildlife.

O'Brien, J. April 1984. Precocious Maturity of the Majid Crab, Puggettia producta, Parasitized by the Rhizocephalan Barnacle. The Biological Bulletin, 166: 384-395.

Ricketts, E., J. Calvin, J. Hedgpeth, D. Phillips. 1985. Between Pacfic Tides, ed.5. Stanford, California: Stanford University Press.

Rudy, Jr, P., L. Rudy. 1987. Oregon Estuarine Invertebrates.