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Sea
Squirts
also known as
ascidians, are a marine class of animals that fall
between the invertebrates and the
vertebrates.
They are simple
animals that are often categorised within the
invertebrates (animal lacking a backbone), howeverin their larval stage they do possess primitive vertebrate
characteristics.
Sea squirts are common on local beaches. They are
sessile animals, with the best places to find them
is under rocks and fixed to large brown
seaweeds.
Depending on the species, sea squirts live
solitary or together in colonies. Solitary forms
are stand alone individuals, while those in
colonies may share “body parts”.
With solitary sea squirts the body has a tunic, a
sturdy outer skin which supports the animal. There
are two siphon openings which allow a flow of
water through the body. Water is drawn through the
inhalant siphon, the water flow being sustained by
the beating of cilia and then expelled via the
exhalent siphon. As the water circulates through
the body; food and oxygen are removed from it; and
waste products and gametes are expelled. The
expelling of water can be in a squirt, (hence the
name) this often happens when a squirt is
handled.
In colonial forms individual squirts share a
tunic. Each squirt has their own inhalant siphon
to draw in the water, but may share an exhalant
siphon. |
