Jenis Crinoid Feather Stars

Crinoid
Feather Stars
Scientific (Genus Species) & Common Names
Phylum: Echinodermata
Subphylum: Crinozoa
Class: Crinoidea
http://www.youtube.com/watch?v=jOAbKWNQu20
General Facts

• Crinoidea comes from the Greek word krinon (a lily) and eidos (form)
• Other Names: Sea lilies, feather starts.
o Sea lilies refer to the crinoids in their adult forms, which are attached to
the sea bottom by their stalks and resembling lilies. Feather stars refer to
their unstalked forms.
• There are two groups of living crinoids:
o Those with columns, the living stalked crinoids.
o Those without columns, the comatulids.
• They come in an array of colors and the size of their living forms are few inches
to a couple of feet in dimension
o However, some extinct crinoids were great in size. One had a stalk of
nearly 21.5 meters. length.
• Their average lifespan is 15 years.
• Their fossils have been used for jewelry. For example, Fossilised crinoid
columnals extracted from limestone quarried on Lindisfarne (UK) or found
washed up along the foreshore were threaded into necklaces or rosaries and
became known as St. Cuthbert's beads.

Evolutionary Relationships
Fossil Crinoid
• Crinoids are the least understood of the living echinoderms, and their skeletal
remains are one of the most abundant and important of fossils.
• There are two competing hypotheses pertaining to the origin of the group:
o The traditional viewpoint holds that crinoids evolved from within the
blastozoans (the eocrinoids and their derived descendants the cystoids)
where the most poplar alternative suggests that the crinoids split early
from among edrioasteroid.
o This debate is hard to settle because they all share many characteristics
including radial symmetry, calcareous plates, and stalks or direct
attachment to the substrate.
• The earliest known group of crinoids date to the Ordovician period (roughly 490
million years ago) and underwent two major adaptive radiations during the
Paleozoic Era (245-570 million years ago).

• They are the most common fossils from Paleozoic-age marine rocks and were
most diverse at this time because they were able to live in shallow water where
plankton was abundant.
• They were able to live in the shallow water where the predators could see them
because Paleozoic predators were less efficient than modern predators.
• Many different kinds of stalked crinoids were able to evolve by specializing on the
kinds and sizes of plankton that they ate because plankton is variable in size and
has a large range of different types of algae and microscopic animals.
• They were major carbonate producing organisms during the Paleozoic and
Mesozoic Eras with entire carbonate shelves composed mostly by crinoidal.
Carboniferous crinoid
• The geological history of the crinoids demonstrates how well the echinoderms
have adapted to filter feeding and the fossils of other stalked filter-feeding
echinoderms, such as blastoids, are also found in the rocks of the Palaeozoic
era.
o Crinoids evolved a plant-like morphology so that they could remain
attached to the seafloor while they spread their arms to catch food.

o Their Pinnules arose in several lineages during the Paleozoic and are
characteristic of all post-Palaeozoic crinoids.
o The comatulids evolved from stalked crinoids by losing their column during
their larval development.
• Crinoids came close to extinction towards the end of the Permian Period, about
250 million years ago.
• The end of the Permian was marked by the largest extinction event in the history
of life and fossil records show that nearly all the crinoid species died out at this
time.
• The one or two surviving lineages eventually gave rise to the crinoids populating
the oceans today.
• The close relatives are starfishes, sea urchins, sea cucumbers, and brittle stars
which reside in the same phylum.
• These species are related to eachother because they share many similar
features.
o For the most part, their body parts are arranged around a central axis.
o They have rough, spiny surfaces which is what their phylum means (“spiny
skin”).
o They have a special kind of radial symmetry based on multiples of five.
o They share a unique body system called the water-vascular system, which
no other group of animals possess.

Physical Traits
Living Crinoid
• They are attached suspension-feeding echinoderms with a cuplike body
supported upward by a stalk or claws (cirri).
• They have a mouth on the top surface facing up surrounded by usually 5
featherlike feeding arms.
• All echinoderms have pentameral symmetry (organization in patterns of 5) and
crinoids can have as few as 5 arms, but usually have arms in multiples of 5.
• They have a u-shaped gut and their anus is located next to the mouth. They also
have sticky mucus covered tube-like feet.
• Most of their body consists of an endoskeleton composed of many calcareous
(composed of calcium carbonate) pieces embedded in their skin called plates or
ossicles.
• The crinoid is encased in the aboral cup, which is typically composed of 2-3
circles of plates.
• Five radial plates (the uppermost circlet of aboral cup plates) are aligned with the
radial water vascular canals and give rise to five arms on the oral side of the
body.

o So each arm is a series of ossicles extending outward from the body.
• The arms contain extensions of coelomic (body cavity), nervous, water vascular,
and reproductive systems
• They also have an ambulacra (radial area) groove bordered by fingerlike tube
feet, or podia, which are extensions of the water vascular system as well. They
are also used in suspension feeding and respiration
• All living crinoids are pinnulate, bearing a small side branch, pinnule, on
alternating sides of successive ossicles along the arm. These pinnules bear the
food-gathering tube feet.
o Pinnules arose in several lineages during the Paleozoic and are
characteristic of all post-Palaeozoic crinoids.
• Crinoids have muscles, nerves, a gut, a reproductive system and other features
Feeding
of advanced animals.
• They are all passive suspension and filter feeders and because they produce no
feeding or respiratory current, they rely more on the water movement around
them, feeding by filtering small particles of food from those seawater currents.
• Their diet consists of a variety of protists (i.e. diatoms and other unicellular algae,
foraminiferans, actinopods), invertebrate larvae, small crustaceans, and detrital
particles.
• To feed they use their featherlike arms that radiates from the central body which
each bears an open ambulacra groove bordered by triads od fingerlike podia

(tube feet) which as mentioned before, are terminal extensions of the water
vascular system.
• This is a complex system of muscles, canals, pouches, bladders, tubes, and
suckers connecting to numerous tube feet that allow Echinoderms to use this
hydraulic system for locomotion, food, waste transportation, and respiration.
• They are also typically nocturnal and will come out after dark to perch upon a
coral or other structure.
• Then they spread out their arms perpendicular to the current to feed, turning their
“plumage” into the current to feed while being restricted to one spot.
• They then their arms and feet to trap their food and flicking/filtering it into their
mouths.
• After a food particle is captured, the shortest tube foot wraps it in mucous
secretions where ciliary tracts on the groove floor then transport it toward the
mouth and ingested.
o The mouth descends into a short esophagus and because there is no true
stomach, it connects directly to the intestine, which runs in a single loop
right around the inside of the calyx.
o The intestine often includes numerous diverticulae (outpouching of a
hollow or a fluid-filled structure in the body), some of which may be long or
branched.
o The end of the intestine opens into a short muscular rectum, which
ascends towards the anus. Waste is collected by phagocytic (white cell)
coelomocytes (immune cells of lower coelomate animals).
• Oxygen is absorbed primarily through the tube feet, which are the most thin-
walled parts of the body, using the water vascular system.
http://www.youtube.com/watch?v=8uZJVSFwixY

Locomotion
• Most crinoids are free-swimming and lack a stem, however stalked crinoids can
move and can reach speeds much higher than 0.6 meters (2ft) /hr
• As previously mentioned, echinoderms utilize the water vascular system to
accomplish a lot of things essential for survival, one of them being locomotion.
• Echinoderms move by utilizing their canals of tube feet and alternately
contracting muscles that force water into the tube feet, causing them to extend
and push against the ground, and then relaxing to allow the feet to retract.
• Echinoderms can use their tube feet or similar extensions of the water-vascular
system to also capture planktonic foods or burrow through substrates.
• On the underside of the calyx, free-living varieties have a ring of specialized short
arms called cirri (claws) that are used for crawling around and for holding on to
surfaces.
• However, they can also actively swim about by rhythmically waving their arms.
http://www.youtube.com/watch?v=MoETr8BNWLQ
http://www.youtube.com/watch?v=cZcomBnNKXg

Avoiding being eaten
• Stalked crinoids today live only in the deep ocean, in quiet water below the
lighted zone where it’s too dark for predators so seem them.
• They live so deep in the water because they are attached to the sea floor and
can’t escape, making them very vulnerable to predators in lighted shallow water.
• They can crawl around on a reef, hiding in crevices during the day and climbing
onto corals at night to feed
• By only feeding at night, they make it harder for predators to find them.

Reproduction and life cycle
• They are dioecious, meaning they separate genders and genitalia.
• They have no true gonads and reproduce by producing their gametes from
genital canals found inside some of the pinnules.
• The pinnules then rupture after some time to release the sperm and eggs into the
water around them.

• The fertilized eggs then hatch to release free-swimming vitellaria larva.
o This larva has rings of cilia running around the body with a tuft of sensory
hairs at the upper pole.
o There have been some cases where the female crinoid has been known
to temporarily brood the larvae using chambers in their arms.
• The larva doesn’t feed and lasts only for a few days before it settles at the bottom
and attaches itself to the underlying surface using a adhesive gland on its ventral
surface.
• The larva then metamorphoses into a stalked adult.
o Free-swimming feather stars sometimes go through this stage too, with
the final stage ending with the adult breaking away from the stalk.
• Within 10-16 months, they are able to produce after becoming adults.
Ecosystem
• They are chiefly deep-sea organisms, mostly inhabiting deep water, usually
attached to sediment resting at the bottom of a stream.
• They relatively live in environments with plankton

• Thy approximate 80 surviving species of stalked crinoids are restricted to depths
greater than 200 m, with the shallowest occurring in 100 m.
• About 65% of living comatulids occur at shelf depths (