THE STEINHART AQUARIUM - Gulf of Guinea Science ...

52 A Docent Field Guide to the Species of the Steinhart Aquarium
Diet: Filter feeders eating plankton, detritus,
and bacteria, using the plumes to sweep food
toward the mouth.
Reproduction and Development: Simple
methods of reproduction. Some species may
reproduce asexually at times. Most have
separate sexes, with poorly defined gonads.
Usually broadcast gametes through excretory
openings into the water. In some species the
worm may leave the tube to reproduce.
Remarks: Tube worms in the family Sabellidae
produce non-calcareous tubes from skin like
secretions. Those in the family Serpulidae
secrete calcium carbonate into their tubes. The
tube mouth is blocked by an operculum when
the worm retracts.
The “featherdusters” are tentacles covered with
microscopic cilia. The cilia move water past the
food groove and capture bacteria and plankton
contained in the water. The food groove is lined
with mucus producing cells. Food particles get
knocked into the mucus, which is thick and
gluey on top, but liquid and mobile below.
The cilia move the mucus carrying the worm’s
dinner into the gut. Essentially, the worm has
produced a conveyor belt to feed itself.
PHYLUM MOLLUSCA
CLASS POLYPLACOPHORA
(CHITONS)
Lined Chiton
Tonicella lineata (Ischnochitoninae)
Distribution: Aleutian Islands, Alaska south
to San Miguel Island, California, west to Sea
of Okhotsk and northern Japan.
Habitat: On rocky substrates covered with
erect or crustose coralline algae in the intertidal
zone and subtidal waters.
Appearance: Length to 5 cm. Body is elongateoval,
valve is low, rounded, smooth and shiny.
Coloration is typically reddish and marked
with sinuous or zigzag lines of alternating
colors of blue, red, whitish; occasionally
blotched or lacking in color.
Diet: Primarily coralline algae.
Reproduction and Development: Spawning
varies by latitude. On San Juan Island,
Washington, eggs are released during May
or June, while in Oregon and California
eggs are released during April. The greencolored
eggs exit the female in groups of
two or three; intermittent spawning lasts
around one and one-half hours. Following
fertilization, the trochophore larvae begins
development for several days as the foot,
mantle and larval eyes form. Larvae settle when
they locate an appropriately hard substrate
containing crustose coralline algae. The larvae
metamorphose into a miniature adult in 12
hours after settlement. The developing shell
valves are initially lightly calcified and thus
very flexible. By the sixth day the diminutive
chiton has all external morphological features
excepting its gills. Thirty days after settlement
it has a fully-developed radula and is equipped
to attack its coralline algae “salads.”
Mortality/Longevity: Predators include the sea
star Pisaster ochraceus.
Remarks: Its coloration blends well with
the substrate of coralline algae. Thus its
appearance is likely an adaptation against
visual predators.
Activity rhythms vary by depth. Individuals in
the intertidal zone don’t move when exposed
during a low tide; they only locomote once
immersed by a rising tide.
Mossy Chiton
Mopalia muscosa (Mopaliidae)
Distribution: British Columbia, Canada to
Baja California
Habitat: On rocks and in tide pools, middle
to lower intertidal in locations with light to
moderate surf; also in estuaries, very unusual
habitat for a chiton.
Appearance: Length to 9 cm. Shell is dull
brown, and frequently eroded and encrusted.
The fleshy girdle surrounding the shell plates
is densely covered with stiff, reddish-brown
bristles; thus the common name.
Diet: Forages exclusively at night. Primarily
feeds upon the red algae turkish towel (Gigartina
papillata) and the green alga Cladophora spp.
In some studies, mossy chiton’s guts contained
up to 15% animal matter, a large percentage
consumed inadvertently.
Reproduction and Development: Spawn
mostly in spring and summer. Eggs and sperm