The abalone somewhat resembles
a snail, the body being little more than a
muscular foot with a head at one end, bearing a
pair of eyes and sensory tentacles. The body is
also fringed with tentacles. Over the top of the
shell lies a line of holes, through which water
is exhaled after it has been drawin in under the
shell and over the gills to extract oxygen. New
holes are formed as the shell grows forward,
while the old holes become covered over, so that
only a few younger holes are open at any one
time, the rest appearing as a line of bumps.
Abalones range in size from the 1-inch-long Haliotis
pourtalese to the red abalone (H.
rufescens), which is a foot across.
Abalones are found along the
coasts of the Mediterranean, Africa, Australia,
New Zealand, the Pacific islands, and the western
coast of North America. Except for two species,
abalones live between the extreme low-water mark
and a depth of about 60 feet along rocky shores
where there is no sand to clog the gills or in
rocky pools large enough not to be heated too
quickly by the sun. H. pourtalese is the
deepest-living abalone, living at depths of 350
to 1,200 feet. The black abalone (H.
cracherodii) lives in the splash zone where
waves breaking against rocks alternately cover
and expose it.
Abalones have no particular
place to which they return after feeding. They
simply hide up in a crevice or under a rock,
avoiding the light and coming out at night. When
disturbed, an abalone grips the rock face, using
its foot as a suction pad -- the two main muscles
of the body can exert a force up to 400 pounds in
a 4-inch specimen.
Movement is achieved by waves
of muscular contractions that pass along the
foot, pushing the animal forward. As each part
expands it is fixed to the ground by slimy mucus
-- the part in front, expanding in turn, is
pressed forward and then itself stuck down.
Alternate waves of movement pass down either side
of the foot, so that as a part of one side is
moving the corresponding part on the other side
stays fixed. The rate of travel is actually quite
rapid for a shellfish -- up to 5 or 6 yards per
minute is possible, but rarely actually achieved.
Abalones are vegetarians,
crawling over rock faces and browsing on seaweeds
that they seek out with their tentacles. Their
favorite foods are red weeds and green sea
lettuces, but they will also scrape tissue off
fragments of kelp that have been torn away by
waves. Food is scraped up and chewed into small
pieces by the rasp-like action of the radula, a
"tongue" made up of large numbers of
small, chalky teeth.
A female releases 100,000 or
more eggs directly into the sea, but only after a
male has released a cloud of sperm around her.
The fertilized eggs are covered by a gelatinous
coat and float freely in the sea until they hatch
a few hours later as minute trochophore larvae.
These larvae are top-shaped and swim around by
means of a band of hair-like cilia around the
thickest part. Within a day the trocophore
develops into a veliger -- a miniature version of
the adult complete with shell but still with the
band of cilia. Two days later it loses the cilia,
sinks to the bottom and starts to develop into an
adult, a process that takes several weeks. Sexual
maturity is reached at about six years.
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