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Trichocysts

Trichocysts are specialized secretory organelles found in many ciliates, a group of single-celled eukaryotes. They consist of elongated, membrane-bound capsules located just beneath the cell cortex and contain tightly packed threads. When discharged, a slender, threadlike filament is expelled rapidly from a pore at one end of the capsule and can extend significantly beyond the cell body. The threads are often coated with adhesive substances and are capable of withstanding rapid elongation.

The discharge of a trichocyst is a rapid exocytotic event triggered by mechanical stimulation, chemical signals,

Trichocysts are a characteristic feature of many ciliates, though not all species possess them. Their size,

or
other
cues
from
the
environment.
The
resulting
thread
can
act
as
a
defensive
weapon,
a
means
to
entangle
prey,
or
to
anchor
the
cell
to
a
substrate.
The
process
is
extremely
fast,
occurring
in
a
fraction
of
a
second,
and
the
filament
remains
in
place
long
enough
to
serve
its
function
before
the
trichocyst
system
resets
and
re-accumulates
threads
for
future
use.
number,
and
discharge
properties
vary
among
taxa.
In
addition
to
their
ecological
roles
in
defense
and
prey
capture,
trichocysts
have
been
of
interest
in
studies
of
rapid
exocytosis
and
cytoskeletal
organization,
contributing
to
broader
understandings
of
cellular
secretion
mechanisms
in
single-celled
organisms.