Like other Aeolid
nudibranchs, this species has its anus on the right side of the body on
an inconspicuous tubercle,
it has dorsal outgrowths such as cerata
(which are cylindrical, lanceolate,
or leaflike but not bushy and are usually arranged in transverse
rows), the rhinophores
stand free and cannot be retracted into a sheath. Aeolidia
loui has many flattened, lanceolate cerata
but a bare area down the middle of the dorsum
with no cerata.
It has no sail-like ridge on the posterior side of its cerata,
at least several rows of cerata
are based anterior to the rhinophores,
less than 1/3 the length of the body, the tail tapers to a blunt point
(is not sharply drawn out into a point) (photo),
anterolateral corners of the foot project as pedal
The body and cerata
are covered with gray to brown spots, especially on the cerata
(some animals may lack pigment). Usually there is a bright
triangular patch on the dorsum over the head just anterior to the rhinophores
are smooth and taper gradually from the base to the tip, which appears
to have a pore in it. Although hepatic
diverticula from the digestive system extend into each of the
the paths of these diverticula are not readily visible from outside if
the animal is pigmented. Color variable but often light
brownish-cream, white, gray, or pink with lighter spots down the center
of the dorsum. It often takes on some of the color
of the anemones
it is eating. Often 3-5 cm long, may attain 6 or even 10 cm.
Common name(s): Shag-rug aeolis, shag rug nudibranch, mossy nudibranch,
shaggy mouse nudibranch, common grey sea slug, maned nudibranch,
aeolid, sea mouse
papillosa, Aeolidia farinacea, Limax papillosa
4.5 cm long, found on a rock in Padilla Bay. This individual
around the side of a dish. The rhinophores
are visible in front with light tips, while one white pedal
tentacle is visible on the extreme right.
|(Photo by: Dave
How to Distinguish
Similar Species: Specimens in our area were formally recognized as A. papillosa but are now classified as a new species, Aeolidia loui. (Kienberger
et al., 2016). Aeolidia papillosa has smooth rhinophores and cerata which remain approximately the same width from base to near the top, while A. loui (the species found here) has "warty" rhinophores and cerata which are wider and thinner at the base than at the tips. Flabellina
salmonacea looks similar but no cerata
are attached anterior to the rhinophores.
A deep-water species, A.
lives at depths greater than 500 m.
Northern or northeast Pacific?
Intertidal to 900
On rocks, or may be on
floats or docks. Often near its perferred prey, Anthopleura
on anemones, especially Anthopleura elegantissima
and secondarily Metridium
senile. Also may feed on Urticina
xanthogrammica, and Epiactis
prolifera, the young of which it may swallow
whole, as well
as sea pens and hydroids. It can detect its prey from a
It apparently does not prey on Anthopleura
artemisia. It is said to be a
voracious predator, consuming
enough anemone tissue to equal half or all its body weight per
It preys on large anemones by first spreading mucus on the column, then
biting off and swallowing chunks. The mucus may shield the
from nematocyst discharge, plus this species' mucus seems to elicit
nematocyst discharge than does the mucus from other, non-anemone-eating
nudibranchs such as Hermissenda
crassicornis or Cadlina
luteomarginata so it may have some inhibitory
may eat Hermissenda or Cadlina,
but Aeolidia eats
the anemone). Tough cuticle in the mouth and esophagus may
those areas from nematocysts. It may eventually eat entire
anemones. After eating Anthopleura
elegantissima which is symbiotic with algae, the
algae may also
be segregated into the tips of its cerata
where they continue photosynthesis. This species is famous
undischarged cnidae (cells which bear nematocysts) from its Cnidarian
and moving them through the hepatic
diverticula to the tips of the cerata,
where they are likely used for defense. If disturbed they
wave their cerata.
If one of the cerata
is broken off, muscles within it contract, expelling the nematocysts,
In SE Alaska this species reproduces late March to late
It lays a white to pinkish, coiled string of eggs in capsules which are
attached to rocks or eelgrass leaves. In Washington, eggs
veligers after 10-24 days.
The nudibranch Phidiana
hiltoni may attack this nudibranch (Goddard et al., 2011)
and Fairbanks, 1966
(as Aeolidia papillosa)
(as Aeolidia papillosa)
and Nybakken, 1980
(as Aeolidia papillosa)
and Hanby, 2005
and O'Clair, 1998
et al., 1985
Goddard, Jeffrey H., Terrence M. Gosliner, and John S.
Impacts associated with the recent range shift of the aeolid
hiltoni (Mollusca: Opisthobranchia) in California.
Marine Biology DOI: 10.1007/s00227-011-1633-7
Harris, Larry G. and Nathan R. Howe, 1979. An
analysis of the defensive mechanisms observed in the anemone Anthopleura elegantissima
in response to its nudibranch predator Aeolidia papillosa.
Biological Bulletin 157: pp. 138-152
Kienberger, Karen, Leila Carmona, marta Pola, Vinicius Padula, Terrence M. Gosliner, and Juan Lucas Cervera, 2016. Aeolidia papillosa
(Linnaeus, 1761) (Mollusca: Heterobranchia: Nudibranchia), single
species or cryptic species complex? A morphological and moleculara
study. Zoological Journal of the Linnean Society 177: pp481-506.
Waters, V. L.,
1973. Food-preference of
the nudibranch Aeolidia
and the effect of the defenses of the prey on predation.
General Notes and
abundances, unusual behaviors:
I have rarely seen this species here near
above was one of two on a large rock in a muddy intertidal area of
Point, Padilla Bay, along with Metridium
senile anemones and chitons.
are flattened, widest above the base, and taper to a point.
diverticula cannot be readily seen within them if there is pigment
The tips often take on the coloration of their anemone food.
mid-dorsal band, which is cerata-free
but has light cororation on it, can be seen to the right.
The foot tapers but is not drawn out into a long, sharp point.
This head-on view shows the white triangle anterior to the rhinophores.
It also shows the smooth, tapering rhinophore
with a light-colored tip, and the fact that the rhinophore
seems to have a pore in the end. Notice also the cerata-free
band that runs mid-dorsally and has light coloration.
This head-on view shows the rhinophores
(the one on the right seems to have been injured and truncated), plus
of the two pedal
tentacles extends to the right.
|In the sequence below, Aeolidia
and briefly attacks a Metridium
giganteum anemone, eliciting the discharge of acontia
from the anemone.
|The nudibranch's first encounter with the anemone
||The nudibranch crawls out onto the column of the
anemone. I did
not see any copious quantities of mucus secreted, but that may be
I placed these two together. Earlier I had placed the
on the column of the anemone but it rolled up into a ball and dropped
|Shortly after the nudibranch crawled out onto the
anemone, the anemone
rapidly contracted and closed up. The nudibranch turned away.
||After the nudibranch left the anemone began
from the column wall.
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