Mitrocoma cellularia (A. Agassiz, 1865)

Common name(s): Cross jellyfish
Synonyms: Halistaura cellularia, Thaumantias cellularia
Phylum Cnidaria 
Order Hydroida 
Suborder Thecata (Leptomedusae) 
Family  Mitrocomidae 
Mitrocoma cellularia from Friday Harbor.  Diameter about 4 cm.
(Photo by: Dave Cowles, July 2009 )
Description:   This hydromedusa has 100-350 unbranched, filiform tentacles which originate at the margin of the bell and are evenly distributed around the margin, long tentacles alternating with short tentacles.  There are no prominent rings or knobs of cnidocytes on the tentacles, which are highly extensile.   The bell is bell-shaped, has a greater diameter than its height, and irregular crease marks are on the exumbrella.  16-24 marginal vesicles containing statocysts occur around the margin of the bell, but there are no ocelli.  The manubrium is attached directly to the subumbrella, not suspended below the bell margin by a gelatinous peduncle.  The 4 lips of the manubrium are long and extended.  The 4 radial canals from the gut do not branch and do not have any major diverticula (longer than the diameter of the canal).  The gonads are linear and associated with the radial canals.  Colorless, or the gonads and/or exumbrella are pale blue.  Diameter to 4 cm.

Structure of polyp (determined in lab--never before reported from the wild):  Generally resembles the catch-all genus Cuspidella.  The colony grows as stolons.   The stem does not have sausage-shaped segments.  The hydranths are enclosed with a distinct hydrotheca.  The gonophores are protected by a gonotheca or similar structure (Group Leptothecata).  The straight-walled hydrothecae are as deep as or deeper than wide and the hydranth can withdraw into them, and they have an operculum. The operculum is merely an extension of the hydrothecal margin, and there are no creases at the base of the opercular plates.  The hydrothecae are sessile (do not arise from pedicels).   The hydrothecae are radially symmetrical and do not have true marginal cusps. Hydroid colonies produce medusae which they set free.

How to Distinguish from Similar Species:  The 4 long, thin radial canals with the long, thin gonads attached to them make a distinctive cross shape which is easy to recognize.  Mitrocomella. polydiademata medusae have 5-9 short tentacles between each set of long tentacles, a smooth exumbrella, and sometimes a pale pink color.  Many other species with numerous tentacles have tentacles all of the same size.

Geographical Range:   Bering Sea to southern CA (medusae--polyps have never been observed in the wild)

Depth Range:  Epipelagic

Habitat:

Biology/Natural History:   This species is common at Friday Harbor.  It luminesces if disturbed in the dark, especially in a band along the margin of the bell.  Medusae appear in May and disappear in late fall.


 
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References:

Dichotomous Keys:
  Carlton, 2007
  Flora and Fairbanks, 1966 (As Halistaura cellularia)
  Kozloff, 1987, 1996

General References:
  Johnson and Snook, 1955 (as Halistaura cellularia)
  Lamb and Hanby, 2005
  Wrobel and Mills, 2003

Scientific Articles:

Web sites:

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


The tentacles are numerous (up to 350), lined up along the margin of the bell (not in clusters), and highly extensible.  In this view most of them are highly contracted.  When extended, long and shorter ones alternate.
 
 

From Monterey Bay Aquarium

Mitrocoma cellularia in Monterey Bay Aquarium.  Photo by Dave Cowles, August 2010


Authors and Editors of Page:
Dave Cowles (2009):  Created original page
CSS coding for page developed by Jonathan Cowles (2007)