This limpet is elongated,
with the right and left margins of the shell nearly parallel for part
its length. The anterior and posterior ends are raised so
limpet fits snugly on a cylindrical surface such as the stipe of an
but does not lit flat on a flat surface (photo).
Iit rocks on a flat surface, leading to the name instabilis).
of shell mostly brown with no ridges and a smooth margin; may be
near apex. Apex is slightly in front of center.
frequently with a central brown blotch and a dark
to about 3.5 cm.
Lottia instabilis (Gould, 1846)
Common name(s): Unstable limpet, Unstable seaweed
instabilis, Acmaea instabilis
|A very large Lottia instabilis
found at Hobuck Beach, on the
open coast near Neah Bay, WA. This shell was empty and washed
on the beach.
|(Photo by: Dave Cowles,
How to Distinguish from
pelta and Lottia ochracea may
live on kelps and be similarly
shaped, but Lottia pelta has prominent ribs and Lottia
has a thin, translucent shell with an external checkerboard pattern.
Range: Kodiak Island, Alaska
to San Diego, CA
Intertidal to 73 m
On the stipes and holdfasts
History: Lives and feeds
on kelp stipes and holdfasts, especially on Laminaria
and Pterygophora californica. In cenral
CA it lives only on
dentigera and L. andersonii. This species runs away quickly
if it contacts
a seastar such as Pisaster
and Fairbanks, 1966 (as Acmaea instabilis)
and Carlton, 1975
and Brusca, 1978 (as Collisella instabilis)
and Snook, 1955 (As Acmaea instabilis)
1993 (As Collisella instabilis)
and McConnaughey, 1985 (As Collisella instabilis)
et al., 1980 (as Collisella instabilis)
Phillips, D.W., and P.
Castori, 1982. Defensive
responses to predatory seastears by two specialist limpets, Notoacmaea
insessa (Hinds) and Collisella instabilis
with marine algae. J. Exp. Mar. Biol. Ecol. 59: 23-30
General Notes and
abundances, unusual behaviors:
|The uneven edges of the shell of
can easily be seen in this end and side view. The shell is
to fit snugly around a round stipe instead of a flat surface.
This species is said to have a brown blotch inside its shell
blotch is not evident in this individual. The shell was found
brown blotch may have weathered away. The anterior
end of the
shell is to the left.
Authors and Editors of
Dave Cowles (2007): Created original page
Jonathan Cowles (2007): Updated page with CSS