Hymenodora gracilis Smith, 1886

Common name(s): 

Phylum Arthropoda
 Subphylum Crustacea
  Class Malacostraca
   Subclass Eumalacostraca
    Superorder Eucarida
     Order Decapoda
      Suborder Pleocyemata
       Infraorder Caridea (true shrimp)
        Family Oplophoridae
Hymenodora gracilis from 2000-2500 m depth  100 mi off Pt Conception, CA. Total length about 5-6 cm.
(Photo by: Dave Cowles, 1993)
Description:  This is a true shrimp from the family Oplophoridae, which lives in deep midwater offshore.  True (Caridean) shrimp have the second abdominal epimera overlapping that of segment 1 and 2.  Family Oplophoridae is almost entirely midwater, has exopodites on its pereopods, and pereopods 1 and 2 are longer and more stout than the others.  Hymenodora are deepliving, non-vertically migrating species that have almost no pigment in their small eyes, giving them a golden color, and usually have very soft exoskeletons (photo) (they are frequently damaged when captured by net).  None of their abdominal segments has a median dorsal ridge. H. gracilis has a short rostrum which extends only slightly beyond the cornea of the eye, maxilliped 2 has a podobranch and an epipod, and the side of the carapace has a V-shaped groove with the apex directed ventrally.  It has a groove passing upward and backward from the middle of the hepatic groove but no groove converging toward the first from the supra-branchial groove.  The telson has 4 pairs of dorsolateral spines.  Unlike the other Oplophorids, which tend to be dark red in deepliving species and half red in vertical migrators, the color of Hymenodora is orange-red, darker on carapace and on eggs.  Maximum length:

How to Distinguish from Similar Species: Hymenodora frontalis has a longer rostrum which extends up to or beyond the distal end of the antennal peduncle.  H. glacialis has no podobranch on the epipodite of maxilliped 2 and has no V-shaped groove on the side of the carapace.

Geographical Range:

Depth Range:  Bathypelagic

Habitat:  Bathypelagic

Biology/Natural History:

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Dichotomous Keys:
  Chace, 1986
  Kozloff 1987, 1996
  Wicksten, 2009

General References:

Scientific Articles:

Chase, Fenner A., 1986.  The Caridian Shrimps (Crustacea: Decapoda) of the Albatross Philippine Expedition, 1907-1910, Part 4:  Families Oplophoridae and Nematocarcinidae.  Smithsonian Contributions to Zoology Number 432.  Paperback, 82 pp.
Wasmer, Robert A., 1967.  Bathypelagic shrimps (Penaeidea and Caridea) from the eastern North Pacific.  M.S. thesis, Walla Walla College, College Place, WA.  86 pp.

Web sites:

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

A closeup of the same individual as above.  Notice the amber eye, which has very little pigment, and the thin, filmy exoskeleton through which the animal's yellowish muscles can be seen.

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