Crangon alaskensis Lockington, 1877 

Common name(s): Northern crangon shrimp; Alaskan bay shrimp, Salt-and-pepper shrimp

Synonyms:
 Neocrangon alaskensis?, Crago alaskensis
Phylum Arthropoda
 Subphylum Crustacea
  Class Malacostraca
   Subclass Eumalacostraca
    Superorder Eucarida
     Order Decapoda
      Suborder Pleocyemata
       Infraorder Caridea
        Family Crangonidae
(Crangon alaskensis from 100 m depth, San Juan Channel, WA.  About 5 cm long.
(Photo by: Dave Cowles, July 2000)
Description:  This shrimp has the typical extremely short rostrum characteristic of many crangonids (photo).  The carapace is smooth and has a median dorsal spine but no submedian spine (photo).  Abdominal segment 6 has no longitudinal dorsal carinae (photo) but the underside does have a median sulcus (photo).  Abdominal segment 5 has no spines on the upper posterolateral margins (photo).  The inner flagellum of antenna 1 is longer than the outer flagellum.  The antennal scale is more than twice as long as wide, has a narrow lamella, and its spine is as long as or longer than the lamella (photo).  The scale is  shorter than the telson.  Length to 6.5 cm.

How to Distinguish from Similar Species: Crangon nigricauda has a shorter antennal scale and spine and is much less slender.

Geographical Range: Bering Sea to San Diego, CA

Depth Range: Intertidal to 275 m.  This species seems to be found more often in deeper, shelf waters than near the intertidal zone.

Habitat: Crangonids often live on sand, which they often burrow into.

Biology/Natural History: This shrimp is one of the crangonids I most commonly find in 100 m depth trawls in the San Juan Channel.  Crangonids are often parasitized by bopyrid isopods such as Argeia.  Crangonids are active predators, eg. on polychaetes.  In Puget Sound some shrimp appear to be hybrids between C alaskensis and C. nigricauda.



 
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References:

Dichotomous Keys:
  Kozloff 1987, 1996
  Smith and Carlton, 1975
  Wicksten, 2009
 

General References:
  Jensen, 1995

Scientific Articles:

Campos, Joana, Claudia Moreira, Fabiana Freitas, and Henk W. van der Veer, 2012.  Short review of the eco-geography of Crangon.  Journal of Crustacean Biology 32:2 pp 159-169

Roberts, James O., 1965.  The anatomy and histology of the eyestalks of the Alaska brown shrimp Crago alaskensis (Lockington).  Masters thesis, Walla Walla College.  23 pp.



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

We frequently catch this species in 100 m depth trawls in the San Juan Channel.



Most crangonids have a very stubby rostrum, seen here as the small "horn" between the eyes for Crangon alaskensis



As with all Crangonids, the first pereopod of Crangon alaskensis is subchelate and the carpus of the second pereopod (visible just above the chela) is simple rather than multiarticulated.



The dactyl of the 5th pereopod is not broad and flattened.



The carapace is smooth and has one median spine a short distance behind the eyes, as can be seen silhouetted in this view from the right side.



The 5th segment of the abdomen (left full segment in this photo) has no spines on the posterolateral margin (right edge of segment),
and the 6th segment (middle of photo) has no longitudinal dorsal ridge.  The uropods and telson are to the right.



The ventral side of abdominal segment 6 has a median groove, visible as the light-colored area in this photo.



The antennal scale of the second antennae, being held out by my finger in this photo,
is more than twice as long as wide and the spine on the end (left side of scale) is longer
than the flatter lamella (right side of end of scale)


A view of the whole, live animal ffom which the parts above were photographed.  Photo by Dave Cowles, July 2005



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