By Dr J Floor Anthoni (2007)
This page details the common seasquirts found
on the New Zealand intertidal rocky shore. Sea squirts are found as mats,
blobs or squirts. They are often very difficult to identify, and can easily
be confused with sponges.
Ascidians Ascidians are seasquirts, ancient organisms and
belong to the Phylum Chordata rather than lower order phyla because
their embryos show what looks like a spinal cord. Seasquirts can be individual,
attached to the rock, or free-floating in the ocean. They can also be mat-forming,
but still individual. Seasquirts can also be communal, each having its
own inlet while sharing a communal outlet. These can be individual or mat-forming.
Seasquirts can be large, the size of a fist or very small, too small to
be distinguished without magnification. Seasquirt mats are easily confused
with mats of encrusting sponges. Some seasquirts can grow old (dozens of
years) whereas others live for only a single season. The seas around New
Zealand have many seasquirt species.
Most seasquirts do not like to become exposed
during low tide, and one finds them underneath stones at the low tide margin.
A seasquirt breathes water in through its inlet siphon on top, and breathes
out through its outlet siphon lower down. Inside the animal, the water
passes through a fine net which strains particles out. Edible particles
are transported towards the mouth by thoudands of vibrating hairs (cilia),
whereas inedible particles are 'coughed' out through the inlet. Wastes
and eggs are passed through the outlet. Seasquirts can be prolific breeders,
producing large numbers of eggs. Some seasquirts can also reproduce by
'budding' off new individuals as the colony spreads.
f019028: the blue star seasquirt (Asterocarpa coerula)
is one of the most comon seasquirts found under stones. It can be wite
to blue. Its blue mouth is star shaped. The barnacles around it are flat
f018931: the glassy seasquirt (Corella eumyota) (3cm)
is easily recognised. Its skin is not slimy but feels firm. The brown and
white patches are bryozoan mats, and the red star is a young oar star.
0704120: the waxy seasquirt (Asterocarpa cerea) is
small, transparent, pear-shaped and cream or brownish in colour, with a
pinkish tinge. Its two siphons are lined in brown/wite. Inhalant siphon
on lef, exhaland in middle, showing brown/white lines.
f052214: the warty seasquirt (Cnemidocarpa nisiotus)
although orange-brown in colour, is well hidden as it allows itself to
be grown over by other organisms, like algae and anemones. Its siphons
are pink/white. The above seasquirt lives in an aquarium.
f052403: two warty seasquirts (Microcosmos kura) attached
to a wall on the Poor Knights Islands. There is a purple crust sponge in
the background and several patches of matting colonial seasquirts.
f052218: the potato seasquirt (Styela plicata) is
a white solitary seasquirt with deep irregular grooves like pleats and
black/white edged siphons at one end.
the intestinal seasquirt (Ciona intestinalis) (6cm)
has a ribbed body, white to brown in coulour with two yellow-collared siphons
at one end. It was introduced from the North Atlantic and North Sea.
the clubbed seasquirt (Styela clava) thrives in highly
degraded water and is probably also an introduced species.
f051631: a glassy dark pink seasquirt (?) being invaded by
seasquirt mats of three kinds.
f027021: the stalked sea tulip (Boltenia pachydermatina)
(previously Pyura d.)stands on a long stalk. It can be pink-red
or white in colour. It is often found just beneath the lower littoral fringe.
f050603: colonial seasquirts like this slimy blob, cannot
easily be identified.
f018918: a slimy plaque of paired colonial seasquirts.
f050806: the clubbed seasquirt (Styela clava) thrives
in highly degraded environments as shown here.
At times bunches of glassy seasquirts or salps can become
washed up on the shore from the open ocean. These are pelagic seasquirts
that propel themselves by the exhaust currents from their siphons.