Page 313 - (DK) Ocean - The Definitive Visual Guide

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CLASS ECHINOIDEA
Sea Potato

Echninocardium cordatum
LENGTH Up to
1
9cm (3 / 2 in)
DEPTH 0–200m
(0–650ft)
HABITAT Sand, muddy
sand
DISTRIBUTION Temperate waters of northeastern
Atlantic

Most sea urchins live in rocky areas,
but the Sea Potato or Heart Urchin
burrows in the sand. Unlike regular
urchins it has a distinct front end and
its spines are thin and flattened.
Special spoon-shaped spines on the
urchin’s underside help it to dig, while CLASS CRINOIDEA while Neocrinus decorus and other, DISCOVERY
longer spines on its back allow water similar sea lilies cannot swim as
to funnel down into its burrow to be Sea Lily shallow-water feather stars do, they FOSSIL EVIDENCE
used for respiration. The dried shell, have been filmed dragging themselves
or test, of this urchin resembles a Neocrinus decorus over the sea bed by their arms. To do Today there are
potato, hence the common name. HEIGHT Up to 60cm this, they appear to break off the end of relatively few sea lily
(24in) the stalk, then re-attach to the substrate species, all of which
DEPTH 150–1,200m using flexible, finger-like appendages live in deep water,
(500–4,000ft) on the stalk. In this way they can but this group once
HABITAT Deep-sea escape from predatory sea urchins. The thrived in ancient
sediments stalk consists of a stack of disc-shaped seas. Entire fossil
DISTRIBUTION Tropical waters of western Atlantic skeleton pieces called ossicles, and sea lilies such as this
Ocean looks like a simple vertebrate spinal one are rare, but
column. Sea lilies feed by spreading out loose ossicles from
Sea lilies are stalked relatives of feather their numerous, feathery arms against their stalks are
stars and usually remain fixed in the the current and trapping plankton. very common in
same place after developing from a Food particles are passed down the some limestones.
settled planktonic larva. However, arms and into the mouth.

CLASS CRINOIDEA body, between the arms. The Tropical
Feather Star clings onto corals using
Tropical Feather Star numerous articulated, finger-like
appendages called cirri. It prefers
Oxycomanthus bennetti elevated positions where it is exposed
DIAMETER to food-bearing currents, and is active
Up to 15cm (6in) by both day and night. Like all feather
DEPTH stars, this species starts its early life by
10–50m (33–165ft) becoming attached to the sea bed by a
HABITAT stalk – at this stage, it closely resembles
Coral reefs a small sea lily. As it matures, the
DISTRIBUTION Tropical waters of western Pacific feather star breaks away and becomes
free-living, leaving the stalk behind.
All that can usually be seen of the
Tropical Feather Star is its numerous
feathery arms held up into the water
to trap food. This species has about
a hundred arms, compared to the
ten that most temperate water
feather stars have. The arms
are attached to a small,
disc-like body and the CLASS CRINOIDEA
mouth is on the
upper side of the Passion Flower
Feather Star called passion flowers by fishermen
because they are brought up in large
numbers by commercial trawlers,
Ptilometra australis
clinging tightly to their nets. These
DIAMETER Up to 12cm feather stars are found in reefs and
(5in)
also in very shallow, sheltered bays
DEPTH To at least 60m and estuaries. Like most feather stars,
(200ft)
the Passion Feather Star is a filter
HABITAT Rocky reefs, feeder that grips onto the tops of
rubble
rocks, sponges, and sea fans, where it
DISTRIBUTION Endemic to temperate waters of spreads its arms wide to trap plankton
southern Australia
and suspended detritus. It remains
This stout feather star has 18–20 arms expanded both day and night but, OCEAN LIFE
with long, stiff side branches called like other feather stars, it can curl
pinnules; the arms are different lengths, up its arms if disturbed or while
giving it a flower-like appearance resting. Its usual colour is a
when viewed from above. They are burgundy red.