Heptacarpus brevirostris (Dana, 1852)

Common name(s): Stout coastal shrimp, stout shrimp, short-spined shrimp
Synonyms:  Spirontocaris brevirostris
Phylum Arthropoda
 Subphylum Crustacea
  Class Malacostraca
    Subclass Eumalacostraca
      Superorder Eucarida
       Order Decapoda
         Suborder Pleocyemata
          Infraorder Caridea
           Family Hippolytidae (broken-back shrimp) (Now in family Thoridae)
Heptacarpus brevirostris from Padilla Bay.  Total length approximately 5 cm.  Identified by Andrew Geigle.
(Photo by: Dave Cowles, July 2006)
Description:  As with other hippolytid shrimp, this species has no exopodites on its pereopods, the carpus of pereopod 2 is divided into 3-7 subunits (articles, a "multiarticulated carpus"), and a rostrum is present but if it has dorsal spines they are not movable.  This species has 7 subunits (articles) in the carpus of pereopod 2, has no supraorbital spines, the rostrum is relatively short, not reaching beyond the first article of the first antennae but reaching at least to the cornea of the eye and having 2-6 large spines dorsally and none ventrally, and the distal portion of article 1 of the first antenna has 3-5 small dorsal spines.  The carapace is nearly as high as it is long.  The third pair of maxillipeds are very large, larger than the pereopods, especially in males.  They have no exopodite but have a tiny epipodite.  The first pereopods are fairy heavy, chelate, and also have a tiny epipod.  The second pereopods are also chelate and are thinner and longer than the first, and have a carpus divided into seven articles (a multiarticulated carpus). Pereopods 3-5 all have bifid tips (photo) and become progressively shorter than pereopod 2.  They are heavier than the second pereopod but more slender than the first.  The third pereopods have epipodites (photo) but the fourth and fifth do not.  The ventral margin of the 4th abdominal pleuron has a spine (photo).  Both uropods are the same length, and are longer than the telson.  Total length to about 5 cm for males and 6.2 cm for females.  Color and pattern highly variable, usually has some brownish or greenish (or even white) and some partly transparent areas, with blue markings.  From my perusal of the descriptions given in the various references cited below, I suspect that this species may actually be a group of several species.

How to Distinguish from Similar Species: Heptacarpus pugettensis has no epipodite on leg 3 and has only 1 dorsal spine on the distal portion of article 1 of the first antenna. H. taylori has a strongly downcurved rostrum which does not reach the cornea of the eye.   Genus Eualus is distinguished from genus Heptacarpus most easily by the fact that Eualus has an exopodite on the 3rd maxilliped and Heptacarpus does not.  Many if not all Heptacarpus were formerly identified as Spirontocaris.

Geographical Range:  Aleutian Islands, Alaska to Santa Cruz, CA

Depth Range:  Intertidal to 128 m

Habitat:  Common in harbors on floats and pilings, and along the open coast in low intertidal and subtidally.  This is the most commonly encountered shrimp in the rocky intertidal of the NE Pacific coast and SE Alaska.

Biology/Natural History:  Predators include the rosylip sculpin Ascelichthys rhodorus.  Parasites include the isopod Bopyrus hippolytes, which lives on the side of the carapace, and the rhizocephalan barnacle Sylon hippolytes whose externa may be seen extending from the abdomen of infested individuals.  In S. British Columbia, females may be seen with eggs from January to August.  The shrimp are common in tidepools but hide by day and come out at night.


 
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References:

Dichotomous Keys:
  Flora and Fairbanks, 1966 (as Spirontocaris brevirostris)
  Kozloff 1987, 1996
  Smith and Carlton, 1975
  Wicksten, 2009
 

General References:
  Harbo, 1999
  Jensen, 1995
  Johnson and Snook, 1955 (as Spirontocaris brevirostris)
  Morris et al., 1980
  O'Clair and O'Clair, 1998
  Ricketts et al., 1985
  Sept, 1999

Scientific Articles:
 

Web sites:


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

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This closeup of the carapace shows the short rostrum which extends past the cornea but not past the first article of the first antenna, with 3-6 stout dorsal spines (some on the carapace), a single tip, and no ventral spines, and no supraorbital spine.

Stygian shrimp

This individual shows another color phase.  This shrimp has a very strange history and shows that this species is capable of a stygian lifestyle.  The shrimp was found living at the bottom of the Rosario Beach Marine Lab seawater reservoir when it was opened for inspection in June 2012.  The seawater pumps had been shut off  since August 2011.  This shrimp and a number of others in the tank must have been sucked through the intake filter screens as larvae in August 2011 at the latest.  They would have had to have grown to full size in the underground seawater reservoir through the 10 winter months of 2011-2012, in total darkness and in uncirculated seawater.  Presumably they ate debris off the bottom of the tank.  The light for this photo is likely some of the first light this shrimp has ever seen.  Carapace length for this individual is about 9 mm and total length is 3.5 cm.  Photo by Dave Cowles, June 2012


Pleons 4-5

The posteroventral corner of the pleurons on abdominal segments 4 and 5 have a sharp point on this species.  Photo by Dave Cowles, June 2012


3rd epopod

This species has an epipod on pereopods 1-3.  This photo shows the coxae at the base of the right pereopods 2 (on the left) to 4 (on the right)  The edge of the carapace can be seen above the legs.  The flaplike epipod can be seen projecting to the right from the dark part of the coxa of pereopod 2 just above the center of the photo.  Photo by Dave Cowles, June 2012.


Bifid dactyls
Dactyls of pereopods 3-5 are bifid (forked at the end).  Photo by Dave Cowles, June 2012.


Authors and Editors of Page:
Dave Cowles (2006):  Created original page