Page 321 - (DK) Ocean - The Definitive Visual Guide

TUNICATES AND LANCELETS 319

SUBPHYLUM TUNICATA SUBPHYLUM TUNICATA Individual star sea squirts are only SUBPHYLUM TUNICATA
about /32 in (2 mm) long and cannot
3
Colonial Sea Squirt Star Sea Squirt live on their own. Instead, they Sea Tulip
arrange themselves in star-shaped
Atrolium robustum Botryllus schlosseri clusters, or colonies, embedded in a Pyura spinifera
HEIGHT WIDTH (CLUSTER) shared gelatinous casing, called a tunic HEIGHT
1
Up to 1 / 4 in (3 cm) Up to 6 in (15 cm) or test. At the center of each star is a Up to 12 in (30 cm)
DEPTH DEPTH shared outgoing (exhalent) opening DEPTH
Shallow water Shore and shallows through which used water is voided. 15–200 ft (5–60 m)
HABITAT HABITAT The colonies vary greatly in color HABITAT
Coral reefs and rocks Rock, stones, seaweeds and may be green, violet, brown, or Rocky reefs
DISTRIBUTION Widespread in tropical reef waters of DISTRIBUTION Coastal Arctic and temperate waters yellow, with the individuals having a DISTRIBUTION Temperate waters of Australia
Indian and western Pacific Oceans of north Atlantic contrasting color to the test.
This giant sea squirt is held up into
Although it appears to be a solitary sea the water on the end of a long, thin
squirt, this species lives in urn-shaped stalk. This means that its large inhalent
colonies that share a single exhalent siphon is in a better position to
siphon (an opening through which pull in plankton-rich water.
water exits). The colony is dotted all The sea tulip’s body is
over with the inhalent, or ingoing, covered in warty
siphons of the tiny zooids—the outgrowths and
individuals that make up the colony. is naturally a
The colony’s green color results bright yellow.
from the presence of the symbiotic However, the
cyanobacterium Prochloron. growth of an
encrusting
commensal
sponge on many
of these sea squirts
gives them a pink
appearance. During
rough weather, sea
tulips are often
battered down onto
the seabed, but they
soon spring back on
their flexible stalks.

Salps are tunicates that resemble
SUBPHYLUM TUNICATA SUBPHYLUM TUNICATA SUBPHYLUM CEPHALOCHORDATA
floating sea squirts. They swim by jet
Salp propulsion, taking in water through Appendicularian Lancelet
a siphon at one end of their bodies
and expelling it at the other. Their
Pegea confoederata Oikopleura labradoriensis Branchiostoma lanceolatum
LENGTH transparent casing is loose and flabby LENGTH LENGTH
Up to 6 in (15 cm) and is encircled by four main muscles About / 4 in (5 mm) Up to 2 / 2 in (6 cm)
1
1
DEPTH that form two distinct cross-bands. DEPTH DEPTH
Near surface Individual salps are joined together Near surface Shore and shallows
HABITAT in chains up to 12 in (30 cm) HABITAT HABITAT
Open water long, produced by the asexual Open water Coarse sand
DISTRIBUTION Warm waters worldwide reproduction (budding) DISTRIBUTION Cold waters of north Atlantic, north DISTRIBUTION Coastal temperate waters of
of a young individual. Pacific, and Arctic northeastern Atlantic, and Mediterranean
The chains break up
and disperse as they Appendicularians are shaped like tiny Looking like a thin, semitransparent,
mature. Salps also tadpoles and live inside flimsy mucus elongate leaf, the lancelet is difficult to
reproduce sexually. dwellings that they build to trap spot in the coarse sediments in which
Eggs are kept inside plankton. Water enters the dwelling it lives. It usually lies half-buried in
the body on the via two inlets covered by protective the sand with its head end sticking
wall of the exhalent grids, passes through fine nets that trap out. Muscle blocks that run along
siphon, through any plankton in mucus, and passes out both sides of its body show through
which the developed through an aperture. The animal eats the skin as a pattern of V-shaped
larvae are expelled the plankton-loaded mucus and beats stripes. At the head end, a delicate
after being fertilized by its tail to create water currents. hood ringed by stiff tentacles overhangs
sperm drawn in through the mouth. This feature filters out
the inhalent siphon. filtering large sediment particles but allows
excurrent nets catch smaller, organic particles
siphon plankton
to pass so that they
The individuals that make up this can be ingested.
SUBPHYLUM TUNICATA
giant, floating, colonial tunicate are
Giant Pyrosome only about 1 in (2 cm) long, but the
colony, which resembles a gigantic
Pyrostremma spinosum hollow tube, can be large enough for
LENGTH a person to fit inside. Each individual
Up to 33 ft (10 m) long lies embedded in the wall of the tube,
DEPTH with one end drawing in nutrient-
Near surface laden water from outside and the
HABITAT other end expelling water and waste OCEAN LIFE
Open water inside. The expelled water is used to
DISTRIBUTION Warm waters between about 40˚ propel the colony as a whole. A wave
north and 40˚ south of bioluminescent light travels along
the community if it is touched.