Key to Class Cephalopoda
Phylum Mollusca
Modified from Kozloff,
1987, 1996 p. 291 (Copyright 1987, 1996, University of
Washington Press. Used in this web page by permission of University
of Washington Press)
With some notes added from Anderson, Roland C.,
2006. On West Coast Octopuses including a field key to west coast
species. The Festivus 38:1 pp 5-6 (San Diego Shell Club).
Dosidicus gigas
is also added, and the description of Benthoctopus leioderma (now Muusoctopus
leioderma) is slightly modified based on our observations of live specimens.
1a |
With 8 arms; arms with sessile suckers; body ovoid and without fins;
without an internal shell or "pen" |
2 |
1b |
With 2 tentacles
in addition to 8 arms; arms with stalked suckers (photo)
and/or hooks (photo); body
rounded to elongate, with fins; with an internal shell or "pen" |
4 |
2a |
Skin of body smooth except for a ridge that borders the
mantle
on both sides; ability to change color limited to lighter and darker shades
of brick-orange; white spots not present on the dorsal
mantle or on the web
in front of the eyes; mantle
length (measured from the body apex to the midpoint between the eyes on
the dorsal mantle)
less than 5 cm [note added: This may not be true in larger specimens];
arms 2-3 times the body length; males without special enlarged suckers
on the arms; without a planktonic
larval stage. With 10-13 lamellae on the outer demibranch
of each gill. Generally found deeper than 500 feet. (Benthoctopus
leioderma in original key) |
Muusoctopus leioderma |
2b |
Skin of body not smooth, but with extensible folds and/or papillae;
capable of changing color freely; color red to red-brown, often mottled
with white; with conspicuous white spots on the dorsal
mantle and on the web in front of the eyes; mantle
length usually greater than 5 cm; arms 3-5 times the body length; males
with 1 or 2 enlarged suckers on the arms; with a planktonic
larval stage |
3 |
3a |
Mantle length frequently
greater than 20 cm and with deep longitudinal wrinkles, weight sometimes
exceeding 50 kg; body with skin folds and large truncate,
paddle-like papillae;
hectocotylus
large, about 1/5 the length of the male's third right arm; with 12-15 lamellae
on the outer demibranch
of each gill; eggs 6-9 mm long; planktonic
larva with a single row of chromatophores
on each arm. (Does not have 3 papillae
under each eye but has 1 white spot centrally located between the eyes
which makes an equilateral triangle with the eyes and a white streak from
each eye to the second arm on each side.) |
Enteroctopus dofleini |
3b |
Mantle length less
than 10 cm, weight less than 200 g; body with small, pointed papillae
[but not the skin folds]; hectocotylus
is small, about 1/10 the length of the male's 3rd right arm; with 11-13
lamellae on the outer demibranch
of each gill; eggs 3-4 mm long; planktonic
larva with a double row of chromatophores
on each arm
(This species also has three prominent cirri
visible below the eye (photo
photo), and 2 white spots
in front of the eyes, which help distinguish it from small specimens of
E.
dofleini) |
Octopus rubescens |
4a |
Body rounded; mantle
length (measured from the body apex to the free edge of the dorsal
mantle) less than 5 cm;
mantle free all around;
fins semicircular, almost as long as the mantle,
with a broad free lobe; arms short, circular in transverse section; tentacles
retractile into special pits; dorsal arms of male modified for spermatophore
transfer
 |
Rossia pacifica |
4b |
Body elongate and tapering; mantle
length usually greater than 5 cm; mantle
attached; fins triangular, generally about half as long as the mantle;
arms long, angular in transverse
section; tentacles
not retractile into special pits; dorsal
arms of male not modified for spermatophore
transfer |
5 |
5a |
Tentacle clubs
narrow, with 2 rows of hooks and with a distinct cluster of modified suckers
that form a "fixing apparatus"; length of fins greater than their width,
and more than half the mantle
length; mantle covered
with fleshy longitudinal ridges; mantle
length commonly exceeding 150 cm |
Moroteuthis robusta |
5b |
Tentacle clubs
without hooks and without a "fixing apparatus"; length of fins equal to
or less than their width, and generally less than half the mantle
length; mantle smooth,
without ridges. |
6 |
6a |
Tentacle clubs
narrow, the suckers large; arms with 2 rows of suckers; arms of unequal
length, the ventral
pair long and broad, and the left ventral
arm of the male modified for spermatophore
transfer; eyes covered by a continuous membrane (cornea); length of fins
equal to their width. |
7 |
6b |
Tentacle clubs
expanded, with numerous minute suckers, 15-20 in each row; arms with 4
rows of armature, the outer rows with suckers, the inner rows with hooks
on all but the ventral
arm pair; arms nearly equal in length, and the left ventral
arm of the male not modified for spermatophore
transfer; membrane over the eyes perforated; width of fins greater than
their length; mantle
length up to 30 cm (specimens collected at floating docks are usually small,
with a mantle length
of less than 10 cm) |
Berryteuthis magister |
7a |
Tentacle clubs
narrow, the suckers large and in 4 rows; arms with 2 rows of suckers, without
hooks; arms of unequal length, the ventral
pair long and broad, and the left ventral
arm of the male modified for spermatophore
transfer; eyes covered by a continuous membrane (cornea); length of fins
equal to their width; mantle
length not exceeding 19 cm |
Doryteuthis opalescens |
7b |
Suckers on tentacle
clubs in 2 rows, arm suckers have hooks (photo),
mantle length up to 150 cm. |
Dosidicus gigas |
Taxonomic Levels Represented in This
Key:
Dosidicus gigas
Enteroctopus dofleini
Muusoctopus leioderma
Octopus rubescens
Rossia
pacifica
Page created by Anna Dyer, 7-2002
Edited by Hans Helmstetler 12-2002, Dave Cowles 2005-
|