Gnathophausia childressi Casanova, 1996

Common name(s): Childress' benthopelagic opossum shrimp
Synonyms:
Phylum Arthropoda
 Subphylum Crustacea
  Class Malacostraca
   Subclass Eumalacostraca
    Superorder Peracarida
     Order Lophogastrida
      Family Lophogastridae (or Gnathophausiidae)
Gnathophausia childressi (captured at 1900 m depth, San Clemente Basin?)
(Photo by: Jim Childress)
Description:  The carapace overlaps almost the entire first abdominal segment dorsally, and ends with a median posterodorsal spine.  The posteroventral margin of the carapace is rounded, without a spine.  Has small supraorbital spines (less well-developed than in other Gnathophausia species).  No antennal spine; branchiostegal spines inconspicuous.  Rostrum is shorter in proportion to body size in larger individuals than in smaller, and has many small teeth along the dorsal margin anterior of the eyes.  Carapace has a high, sharp dorsal crest just behind the rostrum, and a dorsal keel (ridge) which begins just posterior to the crest.  A lateral keel runs longitudinally along the carapace near the ventral margin, ending just anterior to the posteroventral margin.  A vertical groove runs from the anterior end of this keel dorsally to the base of the rostrum, and a second groove angles back from the anterior end of the lateral keel up to nearly the dorsal midpoint of the carapace.  Antennal scales are separated into a proximal and a distal region by an articulation.  The apical spine on the outer margin of the proximal part of the scale reaches to about the middle of the distal part (or to the end of the distal part in small individuals).  Abdomen without a mid-dorsal ridge or posterior-directed mid-dorsal spines.   The second abdominal segment has a transverse groove on the dorsal side.  The anterior lobe of the ventral pleural plates is absent from smaller specimens or rounded and smaller than the posterior lobe in large individuals.  The posterior lobe is pointed in segments 2-5.  Sixth abdominal segments appears to be divided into two parts; anterior portion with platelike pleura and posterior portion with posteroventral spines.  Body length (not including rostrum) to 10.2 cm.

How to Distinguish from Similar Species:  This species is very similar to Gnathophausia affinis, which is also rare and found only in the Atlantic Ocean.  It differs from G. affinis by having:  Only one lateral keel on the carapace instead of two; a longer carapace which completely covers the last thoracic segment, and the dorsal groove on the telson is narrow anteriorly.  Of the local species, it differs from G. gracilis by having no dorsal keel on the abdominal segments, from N. ingens  and N. gigas by having no posteroventral spine on the carapace, and from G. zoea and G. longispina because the lateral keel on the carapace does not curve dorsally as it approaches the posterior margin of the carapace.

Geographical Range:  Collected from the San Clemente Basin and East Cortez Basin, CA.  Not seen in the Santa Catalina basin.

Depth Range:  1708-1940 m

Habitat:  Bathypelagic, living in the benthic boundary layer (within a few tens of meters of the bottom).  Captured within 0.3m of bottom.

Biology/Natural History:  This species seems to stay in the benthic boundary layer of the bathypelagic zone, where particulate abundance is higher than that in the main water column.   The fact that they are benthopelagic may explain why they have been so rarely caught--they are too near the bottom to be caught with a midwater trawl, yet do not rest on the bottom so are rarely caught with benthic trawls.  According to Childress, they can be relatively common in the regions where they occur, but just off the bottom.  The mandibles of this species are smaller and less chitinized than those of most other Gnathophausia.  This has been interpreted to indicate that this species feeds at least partly on the flocculent material in the water instead of by predation.


 
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References:

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General References:
 

Scientific Articles:
Casanova, Jean-Paul, 1996.  Gnathophausia childressi, new species, a mysid from deep near-bottom waters off California, with remarks on the mouthparts of the genus Gnathophausia.  Journal of Crustacean Biology 16:1  192-200

Childress, J.J., D.L. Gluck, R.S. Carney, and M.M. Gowing, 1989.  Benthopelagic biomass distribution and oxygen consumption in a deep-sea benthic boundary layer dominated by gelatinous organisms.  Limnology and Oceanography  34: 913-930

Web sites:
 


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


Another photo of this species by Jim Childress.  These photos are some of the only ones extant of this species shortly after capture.


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