THE STEINHART AQUARIUM - Gulf of Guinea Science ...

54 A Docent Field Guide to the Species of the Steinhart Aquarium
Red abalone have been used as a laboratory
animal in many physiological and biochemical
investigations.
Rough Keyhole Limpet
Diodora aspera (Fissurellidae)
Distribution: Alaska to Baja California.
Habitat: Beneath stones or canopy of algae in
the lower intertidal zone in its northern range,
more common subtidally in the south.
Appearance: Shell to 7 cm long, thick, triangular
in profile. Color gray with radiating grayishbrown,
or black and white radiating striations.
Diet: Omnivorous. Encrusting bryozoans are
consumed in preference to algae.
Reproduction and Development: Spawners.
After various larval stages metamorphose,
larvae settle to substrate and metamorphose
into miniature adults.
Mortality/Longevity: Consumed by sea stars
including the sunflower star and the Pacific
sea star.
Remarks: Upon contact with sea stars this
limpet extends its foot, elevating the shell. The
mantle flap divides at its margin into a series of
folds, two of which extend greatly to cover the
dorsum and ventral surface; thus the starfish
lacks a toehold.
Shield Limpet
Collisella pelta (Acmaeidae)
Distribution: Aleutian Islands, Alaska south
to Baja California.
Habitat: Rocky reefs, mid-low subtidal zones.
Active only when wet or submerged. Associated
with brown algae and mussel beds.
Appearance: Ribbed shell to 4 cm in diameter.
Exterior color highly variable: brown/green;
also colored “checkered” black and white.
Variation at least partially caused by dietary
differences.
Diet: A wide variety of algae, both microscopic
and large. Primarily feeds upon erect algae,
especially the reds (Endocladia muricata, Rhodoglossum
spp., Iridaea spp.), and the browns
(Pelvetia fastigiata, feather boa kelp Egregia
menziesii, and sea palm Postelia palmaeformis).
Reproduction and Development: Spawn
throughout the year in central California.
Young (typically black, with weak shell rib-
bing) occur on the stipes and holdfasts of the
feather boa kelp, Egregia menziesii. They move
to a rock substrate when about 1 cm long, develop
ribbing and change shell color. Reach 3
cm in three years.
Mortality/Longevity: Preyed upon by sea stars
including the ochre sea star (Pisaster ochraceus).
Remarks: Gives an escape response to its three
known sea star predators, but rarely to other
predatory sea stars.
Owl Limpet aka Giant Owl Limpet
Lottia gigantea (Acmaeidae)
Distribution: Washington state to Baja California.
Habitat: Cliff faces and rocks of surf-beaten
high to middle intertidal. At low tide large
individuals occupy a “home scar” in a rock
that exactly fits the margin of their shells. Owl
limpets aggressively defend their territory.
Appearance: Low, oval shell has an eroded
surface; length to 9 cm. Brown shell with
white spots.
Diet: During high tide graze upon algal film
within their territory (appropriately the size of
a large dinner plate; 1000 cm 2 ).
Reproduction and Development: Breed in
autumn and winter in California.
Change sex from male to female.
Mortality/Longevity: Preyed upon by humans
as well as shorebirds such as oystercatchers.
Can live at least 15 years.
Conservation status: Not on IUCN Red List.
However, collection by humans as a food source
threatens many populations. Prized as a food in
Mexico. Illegally poached in California.
Remarks: Owl limpets push smaller limpets
including other Lottia gigantea, mussels and
sea anemones out of its territory by “bulldozing”
(pushing) them with their shell. Small
barnacles are rasped off with its goethite (a
hard iron compound) -capped radula.
Coastal Native American middens often contain
owl limpet shells.
There was once a commercial fishery for
limpets, primarily owl limpets, in California.
During 1919 and 1920 the limpet harvest was
more than 8000 kg.