Armina californica (Cooper, 1863)

Common name(s): California armina

Synonyms: Pleurophyllidia californica
Phylum Mollusca
 Class Gastropoda
  Subclass Opisthobranchia
   Order Nudibranchia
    Suborder Arminacea
     Superfamily Euarminoidea
      Family Arminidae
Armina californica, 6.5 cm long, from 6m depth in Burrows Bay.  Photo taken at Shannon Point Marine Station
(Photo by: Dave Cowles August 2006)
Description:  This nudibranch has white longitudinal ridges on a brownish background.  It has a white or cream line outlining the edge of the dorsum.  Its anus is on the right side of the body, on a papilla in a groove between the dorsum and the foot (photo).  The gills are also located in this groove.  It has no dorsal outgrowths except for the rhinophores.  The rhinophores have longitudinal grooves in the clavus and project anteriorly out of a notch at the front of the mantle (photo).  Length to 7 cm.

How to Distinguish from Similar Species:  This species is very distinctive.  No other local species has the combination of the anus on the right side, longitudinal white ridges on the dorsum, and no cerata.

Geographical Range:  Gulf of Alaska to Panama

Depth Range:  Mostly subtidal, 1 to 230 m

Habitat:  Sandy bottoms

Biology/Natural History:  This species eats sea pens such as Ptilosarcus gurneyi. (or on sea pansies such as Renilla kollikeri farther south where those grow).  May be largely buried in the sand with primarily the rhinophores projecting above the surface of the sand.  Eggs are laid in a pale pinkish-brown spiral chain of capsules.

According to Baltzley et al., (2011), many gastropods, including this species, have a special network of pedal ganglia in their foot which assists in crawling.  The two main neurons involved produce pedal peptides which elicit an increase in the rate of beating of cilia on the foot, resulting in crawling.

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

General References:
  Behrens, 1991
  Kozloff, 1993
  McDonald and Nybakken, 1980
  Morris et al., 1980
  Niesen, 1997
  Ricketts et al., 1985

Scientific Articles:
 Baltzley, Michael J., Allison Serman, Shaun D. Cain, and Kenneth J. Lohmann, 2011.  Conservation of a Tritonia pedal peptides network in gastropods.  Invertebrate Biology 130: 4 pp. 313-324

Web sites:

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

This species has a deep groove along the sides between the wide flap of the dorsum and the wide flap of the foot.  Here the groove on the left side can be clearly seen as the animal turns.

This species has its anus on a prominent papilla on the right side, in a groove between the flaps of the dorsum and the foot.  The view above shows the groove on the right side of the animal, with the anus to the left (posterior) and the gonopore to the right (anterior)

Crawling on surface film
This species can crawl upside-down along the surface film of the water, as shown by this individual crawling along the surface film of
one of our seawater tanks, about 20 cm above another individual crawling along the bottom. Photo by Dave Cowles, August 2015

Armina on Ptilosarcus
This Armina (above) is feeding on a Ptilosarcus gurneyi sea pen. Below are the remains of Ptilosarcus after active feeding by Armina. The central shaft is the rachis.
Ptilosarcus gurneyi eaten by Armina

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