Key: Order Sacoglossa
Phylum Mollusca
Class Gastropoda
Subclass
Opisthobranchia
[Sacoglossans are mostly small, greenish herbivores, though
some species
feed on opisthobranch eggs. Some have shells, while others
have no
shells but have ridges, folds, or papilli
on the back. Most have rolled, tube-like rhinophores]
Taken primarily from Kozloff,
1987, 1996 p. 242 (Copyright
1987, 1996, University of
Washington Press. Used in this web page by permission of University
of Washington Press)
1a |
Cerata
present
(there may also be a pair of rhinophores);
without parapodia
(broad lateral outgrowths of the foot) |
2 |
1b |
Cerata
absent;
with well developed parapodia
that may be turned up to cover the dorsum
or spread flat against the substratum |
Elysia
hedgpethi |
2a |
Cerata
(about
10) limited to the posterior half of the body; body mostly black (head
and tail pale gray) |
Olea hansineensis |
2b |
Cerata
(usually
more than 10) on both the anterior and posterior halves of the body;
body
not black (except in Aplysioipsis smithi) |
3 |
3a |
Without rhinophores;
body slightly flattened; foot broader than the body, tapering abruptly,
not extended posteriorly as a tail (head region with pronounced
dorsolateral
fold; body greenish yellow with black streaks) |
Alderia modesta |
3b |
With rhinophores;
body nearly cylindrical; foot relatively narrow and tapering gradually
to form a pointed tail |
4 |
4a |
Rhinophores
solid (body translucent white, with an intricate reddish brown pattern
on the cerata as well as on the dorsum) |
Stiliger
fuscovittatus |
4b |
Rhinophores
rolled up to form a hollow cylinder, at least for much of their length
(the edges may not quite overlap, however) |
5 |
5a |
Basal portion of rhinophores
solid (only the distal part is rolled up); body black with white around
the mouth, anterior edge of the foot, tips of the cerata,
and within the rhinophores |
Aplysiopsis smithi |
5b |
Rhinophores
rolled up for their entire length; body pale, with a branching green or
red pattern on the dorsum
and within the cerata
(the pattern is formed by branches of the gut and digestive gland) |
6 |
6a |
With as many as 50 slender cerata
(body creamy white, with a green digestive tract) |
Placida
dendritica |
6b |
With only about 18-24 cerata,
these plump rather than slender |
7 |
7a |
Cerata
of nearly
uniform size and shape, and with a yellow cap at the tip; tail short;
digestive
tract reddish brown |
Hermaea oliviae |
7b |
Cerata
of varying
size and shape, and without a color cap at the tip; tail extending
considerably
beyond the ceratal
area and may even equal it in length; digestive tract golden brown |
Hermaea vancouverensis |
Taxonomic
Levels Represented
in This Key:
Elysia
hedgpethi
Placida
dendritica
Stiliger
fuscovittatus
Page created by Dave Cowles, 2006
Edited by:
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