Heptacarpus sitchensis (Brandt, 1851)

Common name(s): Sitka coastal shrimp, Sitka shrimp, Red-banded transparent shrimp, Common coastal shrimp

Synonyms: Spirontocaris sitchensis, Hippolyte sitchensis, Heptacarpus pictus, H. littoralis Heptacarpus sitchensis
Phylum Arthropoda 
Subphylum Crustacea 
Class Malacostraca 
Subclass Eumalacostraca 
Order Decapoda 
Suborder Pleocyemata 
Heptacarpus sitchensis, two individuals about 2 cm long.  Collected intertidally from the N Oregon coast.
(Photo by:  Dave Cowles, April 2014)

Description:  Shrimp of Family Hippolytidae have no exopodites on their pereiopods. Pereiopod 1 is chelate rather than subchelate (photo), and the carpus of pereiopod 2 is subdivided into 3-7 multiarticulated units.  A rostrum is present and often has spines but the spines are not movable.  The eyes project out from under the carapace and are visible from above.  Genus Heptacarpus has a toothed rostrum (photo) and 7 articles in its multiarticulated 2nd carpus (photo). Heptacarpus sitchensis has a well-developed rostrum slightly shorter than the postorbital carapace (photo), but not quite long enough to reach the end of the 2nd antennal scale. The anterior margin of the first segment (base of the peduncle) of the first antenna (antennule) has only one spine where it articulates with the second segment (photo).  The species has no supraorbital spine (photo).  The dactyls at the ends of pereiopods 3-5 have bifid tips (photo).  The rostrum is well-developed and with spines, and reaches beyond the second article of antenna 1 (photo).  It has a pterygostomial spine at the anteroventral margin of the carapace (photo).  The pleuron of abdominal segment 4 has a ventral spine (photo).  Pereiopods 1 and 2 and the 3rd maxilliped may or may not have an epipodite (photo).  Note that this description is at variance with the description in the key but agrees with Wicksten et al. (1996) below.  The 3rd maxilliped is just long enough to reach slightly past the end of the 2nd antennal scale (photo).  Color variable, and is mostly lost at night.  The carapace is often translucent, greenish, with distinctive thin oblique reddish stripes but the background color may be brown or even white.  The legs have red bars.  The abdomen is mostly clear or often bright green (photo).  One reference states that both the carapace and the abdomen may have blue spots.  Total length for females to about 34 mm, males smaller.

How to Distinguish from Similar Species:H. moseri has a much longer 3rd maxilliped which reaches beyond the antennal scale by at least half the length of its distal article, and it typically lives much deeper. H. stimpsoni has a shorter rostrum which reaches beyond the first segment of the peduncle on the 1st antenna but not as far as the middle of the 2nd antennal scaleH. paludicola's rostrum reaches past the end of the 2nd antennal scale.
 

Geographical Range:  Resurrection Bay, Alaska to Baja California
 

Depth Range:  Mid-intertidal to 12 m
 

Habitat:  Can be abundant in mid- and low intertidal of rocky coasts and sublittoral, in Zostera eelgrass beds, and on floats.
 

Biology/Natural History:  This is one of the most common intertidal shrimps along the US Pacific coast.  The variable colors in this shrimp are mainly due to colors in the tissues rather than in the exoskeleton.  The intensity of the color fades when the shrimp has not eaten much recently.  Females mate and brood eggs more than once, molting between broods.  Mating takes place rapidly, shortly after the female molts.  The species may be parasitized by bopyrid isopods, especially in the Salish Sea area, which superficially appear to be a clutch of eggs carried under the abdomen.  In Alaska this isopod species is Hemiarthrus abdominalis

Jensen (2014) says that H. paludicola may be a synonym of this species.
 


References:


Dichotomous Keys:
  Carlton, 2007
  Kozloff, 1987, 1996

General References:
  Jensen (1995)
  Jensen (2014)
  Lamb and Hanby (2005)
  Morris et al., 1980 (as H. pictus)
  O'Clair and O'Clair (1998)
  Ricketts et al. (1985)
 

Scientific Articles:
Bauer, R.T., 1976.  Mating behavior and spermatophore transfer in the shrimp Heptacarpus pictus (Stimpson) (Decapoda: Caridea: Hippolytidae).  Journal of Natural History 10: pp 415-440

Bauer, R.T., 1981.  Color patterns of the shrimps Heptacarpus pictus and H. paludicola (Caridea: Hippolytidae).  Marine Biology 64: pp 141-152

Wicksten, Mary K., Robyn Flynn, and Michael Fagarason, 1996Heptacarpus pictus (Stimpson) synonymized with Heptacarpus sitchensis (Brandt) (Decapoda, Hippolytidae).  Crustaceana 69:1 pp 71-75.  DOI 10.1163/156854096X00097

 


Web sites:
 


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


Rostrum
Heptacarpus sitchensis has a well-developed, toothed rostrum.  None of the teeth are hinged (movable).
This species' tissue is normally nearly clear.  As with many shrimp, the whitish tinge appearing in the tissue here only appears when
the animal is metabolically compromised and dead or nearing death.  Live shrimp run so fast and so constantly that it is almost impossible 
to get clear photos of small body parts.


Pereopods and Maxilliped 3
Being decapods, shrimp such as Heptacarpus sitchensis have 5 pairs of pereiopods (walking legs).  The 5 pairs can be easily
counted in this photo.  Anterior to the walking legs are 3 pairs of maxillipeds, which are legs specially modified for feeding.
In this species the 3rd pair of maxillipeds is large; as long as the legs and more robust.  The first pereiopod has a 
yellow-tipped chela.  The second pereiopod is more slender and has a multiarticulatedcarpus. Pereiopods 3-5 are similar
to one another but in this species their dactyl (tip) is bifid.


Multiculated carpus of the second pereiopod
As with many shrimp, the 2nd pereiopod is thinner and slightly longer than the other walking legs.  The carpus of the 2nd pereiopod,
here draped across the dissecting pin, has a series of constrictions that divide it into seven articles.  This type of structure is called
a multiarticulatedcarpus.


Leg bases
Although Kozloff's key lists epipods at the bases of several pereiopods and the 3rd maxilliped, Wicksten et al., state that this trait is quite variable.
Other references state that the epipods are often very small and hard to see.  This view centers on the 2nd pereiopod (thin leg near middle). The 1st 
pereiopod and 3rd maxilliped are to the right of it and the 3rd and 4th pereiopods are to the left.  None of the leg bases has an obvious epipod.


Bifid dactyl
This view of the propodus and dactyl on pereiopod 4 clearly shows the bifid tip of the dactyl.


Anterior carapace
This dorsolateral view of the carapace shows that the species has no supraorbital spine, which would be just above the
eye near the base of the rostrum.  It also shows that the rostrum is slightly shorter than the postorbital carapace.  The
orbit is the slot in the carapace to accommodate the eyestalk and is the official 'front' of the carapace (not including the
rostrum).  The postorbital carapace is measured from that slot at the base of the eye straight back to the posterior margin.


Pterygostomian spine
Heptacarpus sitchensis has a pterygostomial spine at the anteroventral margin of the carapace, seen here just below the base of the 2nd antenna.


Abdominal pleuron 4-5 spines
The ventral margin of abdominalpleuron 4 (middle-right) of this species has a spine.  Abdominalpleuron 5 (middle-left) has a similar spine.  The third
abdominal segment (top right) of hippolytid shrimp is usually bent, leading to the family name of "broken-back shrimp".


Spine on base of antennule
This dorsal view of the head shows that the anterior end of the basal segment of the first antenna (antennule) has only one
prominent spine near where it articulates with the second segment.


Dorsal view live
This dorsal view of a live individual shows the normally transparent or translucent tissue, the pigmented oblique lines seen on the carapace
and abdomen, and illustrates how the colors can change (compare this view to those above).
 

 



Authors and Editors of Page:
Dave Cowles (2014):  Created original page
CSS coding for page developed by Jonathan Cowles (2007) Salish Sea Invertebrates web site provided courtesy of Walla Walla University