Metacrangon munita (Dana, 1852)

Common name(s): Coastal spinyhead

Synonyms: Crago munitaCrangon munita Metacrangon munita
Phylum Arthropoda 
Subphylum Crustacea 
Class Malacostraca 
Subclass Eumalacostraca 
Superorder Eucarida 
Order Decapoda 
Metacrangon munita, about 4 cm long, captured at 75 m depth in the San Juan Channel
(Photo by Dave Cowles, July 2008  )
Description:   As with all members of shrimp Family Crangonidae, Pereopod 1 is subchelate (photo) and the carpus of pereopod 2 is not divided into several units.  This species has a very short rostrum with a rounded tip (photo) and 5 pairs of legs, the dactyl of leg 5 is not broad and flattened (photo), the carapace has two median spines (photo) and one submedian spine (photo).  The anterior median spine is not larger than the posterior and is set well back on the carapace so that it does not extend past the base of the eye orbits.  Abdominal pleura 1-3 do not have ventrally directed spines (photo), it does not have a prominent longitudinal dorsal ridge on abdominal segments 3-5 (photo), and the tip of the lamella of the antennal scale is longer than the spine (photo).  Males to 3.3 cm length, females to 4.8 mm length.

How to Distinguish from Similar Species:  The coloration of this species is distinctive. Metacrangon variabilis has a prominent longitudinal mid-dorsal ridge on abdominal segments 3-5 and the spine of its antennal scale is longer than the lamella.  The anterior median carapace spine in Metacrangon acclivis is larger than the posterior spine and extends beyond the bases of the eye orbits.  The pleura 1-3 of Metacrangon spinosissima have ventrally directed spines. Mesocrangon munitella has two submedian dorsal spines, and other genera of crangonids usually have none.

Geographical Range:  Central Alaska to southern CA

Depth Range:  12-230 m

Habitat:  Sand bottoms

Biology/Natural History:   This species is nocturnal.  Sometimes parasitized in the gills by the isopod Argeia pugettensis.

Morphologically (not by color) this species is similar to Metacrangon richardsoni from New Zealand.

Genus Metacrangon have two median and one submedian spine on the carapace.  The gastric region of the carapace is depressed below the other regions.  The term "spinyhead" refers to the median and submedian carapace spines (and other spines as well).  Most of the spines are on the end of a supporting carina, or ridge.



Dichotomous Keys:
  Kozloff, 1987, 1996
  Wicksten, 2009

General References:
  Butler, 1980
  Jensen, 1995
  Lamb and Hanby, 2005

Scientific Articles:

Web sites:

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

This ventral view of the head shows that the first pair of pereopods, held closely below the head in this view, is subchelate.

Carapace--side view

In this side view of the carapace, the short rounded rostrum and two median dorsal spines can be seen.  The dorsal profile of the carapace is highest at the posterior median spine and descends anteriorly all the way to the rostrum in a female, while in the male the dorsal profile remains high until the anterior median spine, then descends to the rostrum.  From this view and the animal's size I conclude that this is a female.  Also note that pereopod 5 (the last walking leg) does not have a broad and flattened dactyl.  On the side of the carapace can be seen the light-brown submedian spine, and a hepatic spine just below and forward of it.

Carapace dorsal view

The many spines and setae and the disruptive coloration of the carapace of this species makes it hard to see structures up close.  This is a dorsal view of the carapace, with the head facing right.  The two eyes can be seen on the right.  Between them is the small rostrum, then the mid-dorsal ridge runs back to the left.  The first mid-dorsal spine is visible in the light area at the left of the picture.  In front of the mid-dorsal spine and directly behind the eyes on each side is a single sub-median spine on each side, colored light brown and just to the left of center in this view.

Side view of abdomen

This side view of abdominal segments 2-4 shows that there are no ventrally-directed spines on segments 1-3 and no prominant longitudinal mid-dorsal ridge on segments 3-5.  The first and third pleura have a depression that the larger 2nd pleuron fits over.

Antennal scale

This dorsal view of the head shows the antennal scale (2nd antenna).  Note that the lamella of the scale extends past the antennal spine.

Authors and Editors of Page:
Dave Cowles (2008):  Created original page
CSS coding for page developed by Jonathan Cowles (2007)