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NAME: ASCIDIANS, OR
PHYLUM: CHORDATA; SUBPHYLUM: UROCHORDATA;
OCEANS AND SEAS, FROM
TIDAL POOLS TO DEEP ABYSSES
FEATURES: TYPICALLY SAC-LIKE CREATURES OF VARYING COLORS (YELLOW, RED, BROWN,
AND RARELY BLUE) WITH TWO HOLES (SIPHONS) THAT INJECT AND EJECT WATER FOR
FEEDING, CAN LIVE ALONE, OR IN COLONIES UP TO MANY FEET IN SIZE
DETAILS: Ascidians, or sea squirts, as they are more
commonly known, are stationary creatures for most of their lives, affixing
themselves to the ocean floor, coral, larger shells, algae, or underwater rocks
at a young age and remaining there for their entire lives. Other species
have adapted to living on sandy or muddy bottoms, and are not securely
attached, but have small hairlike growths that help them stay fairly
well-anchored to the surface. Their
bodies are fairly simple structures, consisting of an siphon which takes water
in, another which ejects it, a heart, stomach, gonads, anus, and
intestines. Ascidians are filter
feeders, dieting on plankton and other small particles by inhaling water which
passes over a mucous layer, filtering the particles and passing them to the
stomach, before the water is ejected.
This process of ejecting water is also a defense mechanism which the
ascidian can use to frighten predators away.
Ascidians have an
interesting blood circulation system, in which the heart beats roughly 100
times and pumps the creature’s clear blood in one direction. Then the beating stops for a few moments,
before restarting with the blood flowing in the opposite direction.
Since there are well
over 2000 species of ascidians in the world, the shapes, colors, and
characteristics can vary quite a bit.
Some are large, smooth, and cylindrical, while others are spiny, thin,
and resemble rocks.
Ascidians can either
be solitary creatures, or can live in colonies with others, that can measure up
to 23 feet wide. Solitary ascidians can
measure anywhere from .04 inches to 19.7 inches. Most species, though, are typically less than
one inch in height. Colors vary
throughout the species as well, and can be found in red, brown, yellow, and
occasionally blue. Other species are
transparent, with small colored lines, or spots. Ascidian colonies can be very beautiful, with
different colored species making up varieties of colored patterns and textures.
Ascidians populate all the seas and oceans of the
world, from the shallowest tidal pools, to the deepest depths of the
oceans. Some species have been found
living in depths up to 5000 meters.
There have been cases discovered of ascidians living in brackish and even