The document discusses biology of seastars and feather stars. It provides details about their taxonomy, physical characteristics, habitat, distribution, locomotion, feeding, reproduction, threats and more. Seastars are carnivorous predators related to other echinoderms that use tube feet and a water vascular system to move. Feather stars are crinoids found in warm waters that feed by trapping particles in their feathery arms. While seastars face threats from habitat loss and temperature changes, no feather star species are currently threatened.

1. BIOLOGY OF SEASTAR
AND FEATHER STAR
Vinod Kumar
FRM

2. SEA STAR
 Starfish are also referred to as sea stars because of their star-shaped
appearance.
 They are a part of the phylum Echinodermata and are related to sand dollars,
sea urchins, and sea cucumbers.
 Starfish belong to the class Asteroidea, derived from the Greek words “aster”
(a star) and “eidos“ (form, likeness, appearance).
 There are more than 1600 species of starfish alive today, and they have an
important role in the community structure of the ocean floor.
 All echinoderms share similar pentamerous radial symmetry and spiny skin
characteristics, although sea stars differ slightly because they have five or
more arms large enough to contain space for digestive and reproductive
glands.

3. EVOLUTION AND SYSTEMATICS
 The class Asteroidea is a highly diverse group comprised of seven orders, 35
families, and an estimated 1,600 known living species, although their precise
phylogenetic relationship and hence classification still proves challenging to
taxonomists.
 Kingdom - Animalia
 Phylum - Echinodermata
 Class - Asteroidea
 Order - Brisingida, Forcipulatida, Notomyotida, Paxillosida, Spinulosida,
Valvatida and Velatida and two extinct ones, Calliasterellidae and
Trichasteropsida.

4. Pisaster brevispinus Pisaster giganteus Linckia laevigata
Asterias rubens Pisaster ochraceus Astropecten articulatus

5. PHYSICAL CHARACTERISTICS
 Sea stars vary considerably in size, shape, and color, even within the same
populations.
 Their diverse forms reflect evolutionary adaptation to the cosmopolitan
habitats they occupy.
 Despite this diversity they all share similar physical characteristics. All are
star-shaped (stellate) with a central body or disc that has symmetrically
projecting arms with rows of tube feet running along the lower surface of a V-
shaped furrow called the ambulacral groove.

6.  Typically, the number of arms is
five, but some species such as the
coral-eating crown-of-thorns
Acanthaster planci can have up to
30.
 Patiriella parvivipara, which gives
the appearance of a nearly
spherical body,

7.  In most species, the arm tips carry an optic cushion of red-pigmented and
light-sensitive cells that sense changes in the prevailing environment.
 The skeleton of a sea star consists of small calcium carbonate plates called
ossicles. These are often studded and spiny, and provide a firm but flexible
skeleton of connective tissue.
 Flexibility enables a variety of postures to be adopted without muscular
effort, thus providing an effective means to capture and handle prey and
allow individuals to closely follow irregular substrates in search of food.

9. DISTRIBUTION
 The greatest diversity of sea stars occur in coastal regions, although as a
group, they are well represented globally from the Antarctic, Pacific,
Atlantic, and Indian Oceans.
 They inhabit wave-exposed inter-tidal zones of coastal waters to the calm
sandy pavements of the deepest oceans.
 The Benthopectinidae family of sea stars, for example, lives exclusively in the
deep-sea of the Atlantic and Pacific Oceans, whereas the species Odontaster
validus, which belongs to the family Ganeriidae, are found only in the
Antarctic Ocean.
 Perhaps the most well-known and ubiquitous group of sea stars belongs to the
order Forcipulatida. This group includes the genus Asterias, a veracious
predator of mussels and oysters in many coastal waters around the world.

10. HABITAT
 As a group, sea stars live in virtually every habitat found in the sea, ranging
from tidal pools, rocky shores, sea grass and kelp beds, beneath rock rubble,
on coral reefs, sand, and mud.
 In some species a broad and flattened body may act as a snowshoe when
foraging on very soft mud. In the upper shore, they are periodically exposed
by the retreating tide, resulting in extended periods of desiccation.

11. FEEDING ECOLOGY AND DIET
 Sea stars are carnivorous, preying on sponges, shellfish, crabs, corals, worms,
and even on other echinoderms.
 Most are generalists, feeding on anything that is too slow to escape, such as
mussels and clams, whilst others are specialized feeders preying exclusively
on sponges, corals, bivalves, or algae.
 Prey is located by the chemical odors emanating from its waste products.Or
by small movements that betray its presence when detected by a sea star.
 Several species have specialized feeding behaviors including eversion of their
stomachs..
 This means the starfish extends its stomach out of its mouth and over the
digestible parts of its prey. The prey tissue is partially digested outside of the
body, then the starfish brings its stomach back inside into its 10 digestive
glands to finish feeding.

12.  They have few predators as adults due to their armored spiny skeleton and
rigid nature.
 In less heavily armored and juvenile sea stars, protection from predators
comes from having a cryptic coloration.
 Other defensives include toxic spines or skin (e.g., Crossaster papposus and
Acanthaster planci) and predator avoidance by burrowing beneath the
sediment surface (e.g., Astropecten irregularis and Anseropoda placenta).

13. LOCOMOTION
 On their ventral side, starfish contain thousands of tube-like feet that contain
cells that are specialized for adhesion.
 starfish can use these tube feet to move across a surface. Each foot has two
sets of secretory cells that secrete compounds that allow the foot to first
attach then detach to a surface.
 Sea stars have an unusual way of moving. Water is taken in through the
madreportite, a small, perforated plate on the upper surface of the disc, and
into the water vascular system, a canal of tubes connected to the tube feet.
 Following muscular contraction water is directed under pressure to the tube
feet, which then extend under its force. Movement is achieved through a
coordinated stepping motion where, on muscle contraction, the feet adhere
to the sediment surface, pushing the individual forward.

14. REPRODUCTION
 Most sea stars have separate sexes with no visible differences between them.
 Internally, each arm contains a pair of gonads that become almost filled with
eggs or sperm, depending on the sex, at the time of breeding.
 The majority of species are broadcast spawners where eggs and sperm are
released into the water column to be fertilized.
 To increase the chances of fertilization, sea stars aggregate when they are
ready to spawn.
 Asexual reproduction is another method of development that involves either
fission or regeneration of entire animal from arm parts.
 Almost a dozen species divide through their disc, producing clones with
identical genetic makeup (e.g., Linckia laevigata).

16. BEHAVIOUR
 Sea stars have a "central nervous system," or diffuse nerve net, but lack
anything identified as a brain.
 Despite this, they are sophisticated enough to adapt to change based on
previous experiences (conditioning), whereby behavior that is persistently
unsuccessful, usually a feeding one, is stopped.
 They are not considered social animals, yet many species tend to aggregate or
swarm in large numbers during certain times of the year.

17. RESPIRATION
 Sea stars don't use gills or lungs to breathe.
 They rely on diffusion across surfaces in their body.
 For example, most oxygen is taken up from water that passes over their tube
feet and papulae or skin gills.

18. EXCRETION
 Starfish have no distinct excretory organs; waste ammonia is removed by
diffusion through the tube feet and papulae.
 The body fluid contains phagocytic cells called coelomocytes, which are also
found within the hemal and water vascular systems.

19. WATER VASCULAR SYSTEM
 The water vascular system is a hydraulic system used by echinoderms, such as
sea stars and sea urchins, for locomotion, food and waste transportation, and
respiration.
 The system is composed of canals connecting numerous tube feet.
 The exact structure of the system varies somewhat between the five classes
of echinoderm.
 The system is part of the coelomic cavities of echinoderms, together with the
haemal coelom (or haemal system), perivisceral coelom, gonadal coelom and
perihaemal coelom.

20. Threats and conservation status
 The biggest threats to starfish are a reduction of coral reef habitat, pollution,
and marked changes in water temperature.
 The iconic sunflower sea star has been listed as critically endangered by the
International Union for Conservation of Nature following a groundbreaking
population study led by Oregon State University and The Nature Conservancy.

21. FEATHER STAR
 feather star, any of the 550 living species of crinoid marine invertebrates
(class Crinoidea) of the phylum Echinodermata lacking a stalk. The arms,
which have feathery fringes and can be used for swimming, usually number
five.
 Feather stars use their grasping “legs” (called cirri) to perch on sponges,
corals, or other substrata and feed on drifting microorganisms, trapping them
in the sticky arm grooves.
 A feather star is not the same as a starfish (also known as a sea star and
sometimes misspelled as star fish).
 Close relatives of feather stars include sea stars, brittle stars, sea cucumbers
and sea urchins.

22. HABITAT
 A feather star habitat is slightly different from a starfish habitat.
 Feather stars, also called crinoids, reside in the ocean, typically in shallow,
warm waters. Some species do, however, exist in colder waters and deeper
areas.
 A sea star or starfish habitat needs the right surface for the creature's feet to
move across. Sea stars with tube feet reside among rocks, and sea stars with
pointed tube feet tend to live on the seabed in sand or mud.
 Feather stars, however, live in areas with strong currents. They do not tend to
live around silt, which can clog their feet. Living in areas with these currents
ensures their survival, as they yield more opportunities to capture food.
 They may also swim through the water column if disturbed.

23. DISTRIBUTION
 They are most abundant from the Indian Ocean to Japan.
 where Tropiometra is the commonest genus. Antedon is the best known genus
in the Atlantic.

24. SYSTEMATICS
 KINGDOM - ANIMALIA
 PHYLUM - ECHINODERMATA
 CLASS - CRINOIDEA
 ORDER - COMATULIDA
 Feather star species distributed among 150 genera and 17 families in one
order.

25. Comaster nobilis Oxycomanthus bennetti Himerometra robestipinna
Antedon mediterranea Leptometra celitica Nemaster grandis

26. LOCOMOTION
 These amazing creatures swim, float and “walk” through the sea.
 Feather stars swim by beating their arms up and down, or at times
parachuting with their cirri out to grasp new substrate.
 When needed, however, feather stars can attach to rocks or other materials
via their cirri.
 Feather stars previously were not considered fast movers.

27. FEEDING BIOLOGY
 They feed on small food particles, which they pick up by moving their
feather-like arms. After they grab some food, they push it toward their
mouth, which is in the center of their body.
 They usually inhabit shallow waters, and they prefer a reef with a bit of
current so the food comes directly to them.
 Feather stars are usually nocturnal, but you can also observe them swimming
or moving their tentacles during the day when they’re feeding or moving from
one coral to another.

28. REPRODUCTIVE BIOLOGY
 Male or female feather stars reproduce via water fertilization. Eggs,
produced in spring, hatch as larvae. The swimming larvae eventually
attach to the sea bottom via stalks
 The fertilised eggs hatch to release free-swimming vitellaria larvae.
The bilaterally symmetrical larva is barrel-shaped with rings of cilia
running round the body, and a tuft of sensory hairs at the upper pole.
 Crinoids are not capable of clonal reproduction as are some starfish
and brittle stars, but are capable of regenerating lost body parts.

29. WATER VASCULAR SYSTEM
 Like other echinoderms, crinoids possess a water vascular system that
maintains hydraulic pressure in the tube feet.
 This is not connected to external sea water via a madreporite, as in other
echinoderms, but only connected through a large number of pores to the
coelom (body cavity).
 The main fluid reservoir is the muscular-walled ring canal which is connected
to the coelom by stone canals lined with calcareous material.

30. NERVOUS SYSTEM
 The crinoid nervous system is divided into three parts, with numerous
connections between them.
 The oral or uppermost portion is the only one homologous with the nervous
systems of other echinoderms. It consists of a central nerve ring surrounding
the mouth, and radial nerves branching into the arms and is sensory in
function.
 Below this lies an intermediate nerve ring, giving off radial nerves supplying
the arms and pinnules. These nerves are motor in nature, and control the
musculature of the tube feet.

31. Threats and conservation status
 The main threats are recreational fishing, commercial fishing with gillnets,
and habitat degradation.
 No species are listed by the IUCN.

32. CONCLUSION
 Sea stars are related to sand dollars, sea urchins, and sea cucumbers, all of
which are echinoderms, meaning that they have five-point radial symmetry.
However, this does not mean that all sea stars have five arms and species
with 10, 20, or even 40 arms exist.
 Pycnopodia helianthoides, commonly nown as the sunflower sea star, is a
large sea star found in the northeast Pacific.In 2020, the IUCN first assessed
that the sunflower sea star was critically endangered.
 Feather stars are a type of marine invertebrate with featherlike arms that
radiate from a central body.
 Feather stars are not considered threatened or endangered.

33. REFERENCES
 Lawrence, J. M. (Ed.). (2013). Starfish: biology and ecology of the Asteroidea.
JHU Press.
 Garm, A. (2017). Sensory biology of starfish—with emphasis on recent
discoveries in their visual ecology. Integrative and Comparative Biology, 57(5),
1082-1092.
 Vogler, C., Benzie, J., Lessios, H., Barber, P., & Wörheide, G. (2008). A threat
to coral reefs multiplied? Four species of crown-of-thorns starfish. Biology
letters, 4(6), 696-699.
 Holland, N. D. (2020). Cell cycle in regenerating feather star arms. In
Echinoderms through time (pp. 217-220). CRC Press..

34. THANK YOU