Pugettia producta (Randall, 1839)

Common name(s): Shield-backed kelp crab, Northern kelp crab, Kelp crab

Synonyms:  Epialtus productus, Pugettia productus Pugettia producta
Phylum Arthropoda
 Subphylum Crustacea
  Class Malacostraca
   Subclass Eumalacostraca
    Superorder Eucarida
     Order Decapoda
      Suborder Pleocyemata
       Infraorder Brachyura (true crabs)
        Family Majidae (Now in Family Epialtidae)
Pugettia producta from Sharpe Cove dock (running from me).  Carapace length 6 cm.
(Photo by: Dave Cowles July 2011)
Description:  This majid crab can grow fairly large.  Its rostrum consists of two flattened processes.  The carapace is longer than wide.  It has a sharp lateral projection at or behind the middle (photo).  The dorsal carapace surface is almost smooth.  The distance between the eyes is less than about 1/3 the carapace width.  Color greenish brown to maroon dorsally, reddish or yellowish ventrally (photo photo).  Young crabs are brown, red, or olive green.  Carapace width to 9.3 cm in males and 7.8 cm in females.

How to Distinguish from Similar Species: Pugettia gracilis does not grow as large, and its dorsal carapace is rough. Scyra acutifrons has a rounder, rougher carapace.  The carapace of Hyas lyratus is wider in front, and is also rougher.   Cancer productus is a cancer crab (and has a round carapace and no rostrum)

Geographical Range:  Chichagof Island, Alaska to Ascuncion Point, Mexico

Depth Range:  Intertidal to 73 m

Habitat:  Mostly in kelp beds, either on the bottom or climbing in the kelp (photo).  Also common on pilings.  Juveniles may be in tidepools or around surfgrass or  Fucus.

Biology/Natural History:  This species does not decorate itself as much as some other majid crabs do.  It does have two rows of hooked setae just behind its rostrum, to which it sometimes attaches algae, etc.  The items it attaches may be mainly food, which it detaches and eats later.  This crab eats algae such as Fucus, Macrocystis, Nereocystis, Sargassum, Egregia, Pterygophora, and red algae.  Where algae is scarce they may eat barnacles, mussels, hydroids, and bryozoans.  Predators include staghorn sculpins, gulls, cabezon, and sea otter. Velella velella, the by-the-wind sailor, will readily capture and eat the pelagic larvae (zoeae).  The species is sometimes parasitized by the rhizocephalan sacculinid barnacle Heterosaccus californicus, which causes the crabs to be sluggish and to have a brownish mass (the reproductive parts of the barnacle) protruding from under the abdomen. The crab molts only once after being parasitized, and during that molt the barnacle's reproductive sac pushes out through the surface.  The crab's gonads are damaged or destroyed and males exhibit some female-like characteristics such as a broad abdomen and small claws.  He may even become a hermaphrodite and produce eggs as well as sperm.  Females seem less affected other than speeding up the development of mature female characteristics.  This species cannot osmoregulate so it cannot tolerate diluted seawater.  The species has a terminal molt, after which the carapace may become partly overgrown with barnacles, etc.  In the fall adults migrate to deeper water where they congregate, feed, and mate.  Females may be carrying eggs during most seasons of the year.  In southern Puget Sound females could not be found during May, September, and October.  Clutch size ranges from 34,000 to 84,000 eggs.  Freshly extruded eggs are bright orange, maturing to red, and to grayish-purple at hatching.  Embryonic development may require nearly a year.  Note:  The long legs and claws of these crabs are dextrous and they can cling tenaciously and pinch hard, so be warned.



 
 
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References:

Dichotomous Keys:
  Coffin, 1952
  Flora and Fairbanks, 1966
  Hart, 1982
  Kozloff 1987, 1996
  Smith and Carlton, 1975
  Wicksten, 2009
 

General References:
  Brandon and Rokop, 1985
  Brusca and Brusca, 1978
  Gotshall, 1994
  Harbo, 1999
  Hinton, 1987
  Jensen, 1995
  Johnson and Snook, 1955 (as Epialtus productus)
  Kozloff, 1993
  McConnaughey and McConnaughey, 1985
  Morris et al., 1980
  Niesen, 1994
  Niesen, 1997
  O'Clair and O'Clair, 1998
  Ricketts et al., 1985
  Sept, 1998

Scientific Articles:
Hultgren, Kristin M. and John J. Stachowicz, 2008.  Alternative camouflaage strategies mediate predation risk among closely related co-occurring kelp crabs.  Oecologia 155: 519-528

Web sites:



General Notes and Observations:  Locations, abundances, unusual behaviors:

While this crab is common among kelp in some places along the coast, it is not very common (though present) near Rosario.



Underside

A view of the underside.



This individual, photographed underwater, is clinging to the stalks of Nereocystis kelp.  Photo July 2005 by Jim Nestler

View from above and below of another individual.  This male was found clinging to the dock in Sharpe's Cove.  Photos by Dave Cowles, August 2012
Dorsal Ventral


This individual is running across a tidal flat at Shi Shi beach at low tide, leavng a crab trail behind.  Note that, like all crabs, it runs sideways.

Mating pair

This pair was found at Beach #4 at Kalaloch.  The smooth male (facing the camera) is clinging tenaciously to a larger female, who is encrusted with colonial tunicates.  Male crabs often hold and protect a female until she molts, then breed with her while her gonopores are soft.  The abundant tunicate growth on this female suggests that she has not molted for a long time, so she may be due for a molt soon.  Note that the underside of this male is more red than the underside shown above.  Photo by Dave Cowles, July 2009.



Authors and Editors of Page:
Dave Cowles (2005):  Created original page