THE STEINHART AQUARIUM - Gulf of Guinea Science ...

60 A Docent Field Guide to the Species of the Steinhart Aquarium
Diet: Filter feeds but majority (perhaps approaching
90%) of nutrition is a result of the
activities of intercellular endosymbiont zooxanthellae
that live in blood sinuses within
the mantle.
Reproduction and Development: Initially attached
to substrate with byssal threads. Grow
very rapidly during the first 2 years.
Mortality/Longevity: May reach adult size
when 30 years old.
Conservation status: IUCN listed as Threatened.
Tridacna clams are being heavily exploited
as a food item for humans. The meat
of a single conspecific individual (T. gigas)
was recently poached and sold (for $3.00 vs.
the $300.00 retail rate) in Papua New Guinea.
Remarks: The pigments in the mantle probably
reduce light intensity to protect zooxanthellae
from overexposure.
Scallop aka Swimming Scallop
Chlamys spp. (Pectinidae)
Distribution: Gulf of Alaska to San Diego.
Habitat: Mostly subtidal, or sometimes
intertidal, at depths of 2–150 m.
Appearance: Up to 6 cm in length. Convex valves
with ribs radiating from umbo (prominence near
the hinge) to ventral edge, and covered with
prominent spines or ruffles. Usually has sponges
encrusting on its surface.
Diet: Filter feeds about 4 liters of water per
gram per hour, using their ctenidia (or gills) to
collect microscopic food and oxygen.
Reproduction and Development: Sexes are
separate. Veligers (free swimming, planktonic
larvae) arise 50 hours or so after eggs are
fertilized. Shells form annual growth rings.
Mortality/Longevity: This scallop lives about
6 years (at least in Southern British Columbia.)
A variety of sea stars prey on this mollusk.
Also, is parasitized by Odostomia columbiana,
the clam sucker snail, so called because it uses
its eversible proboscis to suck body juices from
its host.
Remarks: Escapes predators by swimming,
forcing water out as a jet near the bivalve’s
hinge. Encrusting sponge and scallop are in a
mutualistic relationship. The sponge repels sea
star predators, possibly by chemical secretions;
the scallop’s movement may reduce sediment
accumulation on sponges.
Has several hundred eyes at edge of mantle;
these detect light and dark, but do not form
images.
Giant Rock Scallop
Crassedoma giganteum (Pectinidae)
Distribution: Common from British Columbia
to Baja.
Habitat: In or on rock crevices, pilings, and
floats; intertidal to 50 m.
Appearance: Typical scallop shape. While most
scallops grow to c. 18 cm, this giant can reach
30 cm in diameter. Females larger than males.
Diet: Filter feed on plankton and suspended
organic particles.
Reproduction and Development: Protandrous
hermaphrodites. Usually spawn in spring,
April to mid-June depending on latitude.
Larvae are planktonic.
Mortality/Longevity: Live to 25 years.
Remarks: Juveniles can swim. At about 2.5 cm
diameter, individuals cement to rock or other
hard surface with byssal threads.
Humans gather rock scallops and consume the
adductor muscle, raw or fried.
CAS displays casts of the real thing, as they
are extremely difficult to maintain in captivity.
CLASS CEPHALOPODA
Chambered Nautilus
Nautilus pompilius (Nautilidae)
Distribution: Eastern Indian Ocean to Fiji.
Habitat: 60–750 m. Rise to shallower depths
each evening.
Appearance: Snail-like shell lined with alternating
wavy brown and white lines. Circumference
to 20 cm.
Diet: Migrate to shallower waters each evening
to feed. Benthic scavenger and predator. Prey
located visually. Preferentially eat decapod
crustaceans, such as crab, also carrion.
Reproduction and Development: Males have
a modified arm which functions to transfer a
sperm packet. Fertilization occurs much later
when the eggs are deposited. Mature at one year.
Mortality/Longevity: Eaten by carnivorous
fishes.
Conservation status: Collected for the shell