Key to Order Nudibranchia

Phylum Mollusca
 Class Gastropoda
  Subclass Opisthobranchia

[Nudibranchs have exposed, unprotected gills.  Adults have no shell (the larval shell is lost).]

Taken primarily from  Kozloff, 1987, 1996  (Copyright 1987, 1996, University of Washington Press.  Used in this web page by permission of University of Washington Press)
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1a Anus, partly or completely encircled by gills, located on the midline of the dorsum, one-half to three-fourths of the body length from the anterior end Suborder-
Doridacea
(In part)
1b Anus not located on the midline of the dorsum ( it is either on the right side, on the dorsum near the right side, or at the posterior end of the body; if gills are present, they are not arranged in a partial or complete circle around the anus) 2
2a Anus at the posterior end of the body, on the midline, in a deep groove in the mantle between the foot and the edge of the dorsum; dorsum without any outgrowths other than the rhinophores Suborder-
Doridacea
(In part)
2b Anus on the right side of the body, or on the dorsum near the right side; dorsum usually with outgrowths (simple or branched cerata, or gills) in addition to rhinophores ( if dorsal outgrowths are not present, the dorsum has several white longitudinal ridges on a pinkish brown background) 3
3a Without dorsal outgrowths other than the rhinophores; dorsum with several white longitudinal ridges on a pinkish brown background Suborder-
Arminacea:
Armina
californica
3b With dorsal outgrowths (cerata or gills) in addition to the rhinophores; dorsum without white longitudinal ridges 4
4a Clavus of the rhinophores partly or fully retractile into the sheath; dorsal outgrowths either club-shaped cerata (with rings of prominent tubercles), paddlelike or bushy cerata, or bushy gills (as a rule, there are 4 to 10 cerata or numerous gills arranged in each of 2 dorsolateral longitudinal series) Suborder-
Dendronotacea
4b Clavus of rhinophores not retractile into a sheath (each rhinophore stands free; it has no sheath); dorsal cerata cylindrical, lanceolate, or leaflike, usually numerous (more than 20) and usually arranged in transverse rows 5
5a Anus on a conspicuous papilla near the right side of the posterior third of the dorsum, usually among the posterior third of the cerata Suborder-
Arminacea
(in part)
5b Anus on an inconspicuous papilla near the right side of the anterior half of the dorsum, usually among the anterior third of the cerata Suborder-
Aeolidacea



Taxonomic Levels Represented in This Key:

  Suborder Aeolidacea
  Armina californica
  Suborder Arminacea
  Suborder Dendronotacea
  Suborder Doridacea



Page created by Robbie Wheeling, 7-2002
Edited by:  Dave Cowles 8-2002, 2005
                 Hans Helmstetler 1-2003