Corals are marine invertebrates in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". Corals are gastrovascular marine organisms. Each one of these animals is known as a coral "polyp". Coral Polyps are tiny, primitive marine organisms. A single polyp has a tube-shaped body with a mouth which is surrounded by tentacles. The polyp of hard corals produces a stony skeleton of calcium carbonate which form the base. Often the skeleton forms a cup-like structure in which the polyp lives. Coral polyps in colonies make up the cora reefs.

1. Biology of coral
Submitted by
VINOD KUMAR

2. Introduction
 Corals are marine invertebrates in class Anthozoa
of phylum Cnidaria typically living in compact
colonies of many identical individual "polyps".
 Corals are gastrovascular marine organisms. Each
one of these animals is known as a coral
 "polyp". Coral Polyps are tiny, primitive marine
organisms.
 A single polyp has a tube-shaped body with a
mouth which is surrounded by tentacles.
 The polyp of hard corals produces a stony skeleton
of calcium carbonate which form the base. Often
the skeleton forms a cup-like structure in which
the polyp lives. Coral polyps in colonies make up
the cora reefs.

3.  A coral polyp is a soft, almost transparent animal which
builds its own skeleton outside its body. Since it has no
backbone, it is an invertebrate.
 Coral reefs have optimal growth rates in warm water
ranging from 21-29°C.
 A coral polyp has three main parts.
 They are its base, mouth and a middle portion. The base
of the polyp is attached to its skeleton.
 The mouth (or) open end, has tentacles around its edge.
 The middle section is shaped like a tube. It has a hollow
space inside and is known as the gut.
 A polyp is made up of two cell layers as : the epidermis
and the gastrodermis. The non-tissue layer between the
gastrodermis and the epidermis is called the mesoglea.

4. Polyp
 The coral head is the familiar visual form of a single
organism, it is actually a group of many individual , yet
genetically identical , multicellular organisms known as
polyps.
 Polyps are usually a few millimeters in diameter, and are
formed by a layer of outer epithelium and inner jellylike
tissue known as the mesoglea.
 They are radially symmetrical , with tentacles surrounding a
central mouth, the only opening to the stomach or
coelenteron, through which food is ingested and waste
expelled.

6. Scientific classification
 Kingdom: Animalia
 Phylum : cnideria
 Subphylum: anthoza
 Class :Hexacorallia, Ceriantharia, Octocorallia
 Subclasses : Alcyonaria, zoantharia
 Orders : Alcyonacea, Helioporacea, Antipatharia,
Corallimorpharia, Scleractinia, Zoanthidea

7. Zooxanthellae
 Zooxanthellae is a colloquial term for single-celled dinoflagellates that are
able to live in symbiosis with diverse marine invertebrates including
demosponges, corals, jellyfish, and nudibranchs.
 Most known zooxanthellae are in the genus Symbiodinium

8. Feed & Feeding
 Most reef-building corals have a mutually beneficial relationship with a
microscopic unicellular algae called zooxanthellae (also known as
Symbiodinium) that lives within the cells of the coral's gastrodermis.
 As much as 90 % of the organic material the algae manufacture
photosynthetically is transferred to the host coral tissue.
 In addition to the symbiotic relationship with algae, most corals capture and
consume live prey ranging from microscopic zooplankton to small fish,
depending on coral size.
 Using its tentacles that extend outside it body, the coral with utilize it
nematocysts, or stinging cells, to stun and kill its prey before passing it to its
mouth. Once the food has been digested, the waste is expelled from the
same opening.

11. Types of coral
 Hermatypic Corals
 Hermatypic corals in the order Scleractinia are stony corals that build reefs.
 They mostly obtain their energy requirements from
zooxanthella(Symbiodinium), symbiotic photosynthetic microalgae.
 They secrete calcium carbonate to form a hard skeleton.
 This group includes reef-building corals (scleractinians), sea anemones and
zoanthids. Hermatypic genera include Scleractinia, Millepora,Tubipora and
Heliopora.

12.  Ahermatypic Corals
 Ahermatypic corals have no zooxanthella (Symbiodinium).
 They include corals in subclass Alcyonaria, as well as some
species in order Anthipatharia (black coral , Cirripathes,
Antipathes).
 Ahermatypic corals, such as sea whips, sea feathers, and
sea pens, are also known as soft corals.
 Unlike stony corals, they are flexible, undulating in the
current, and often are perforated, with a lacy
appearance.
 Their skeletons are proteinaceous, rather than calcareous.

13. Reproduction
 Coral can reproduce both gonochoristic (unisexual) and hermaphroditic
 Reproduction also allows coral to settle in new areas

14. Sexual reproduction
 Corals predominantly reproduce sexually.
 About 25% of hermatypic corals (stony corals) form single sex (gonochoristic)
colonies, while the rest are hermaphroditic.
 Sexual reproduction is the more common method and can be performed in
two ways:
 Broadcast spawning .
 Brooding.

15. Broadcasters
 About 75% of all ; hermatypic corals "broadcast spawn" by releasing gametes
—eggs and sperm into water to spread offspring.
 The gametes fuse during fertilization to form a microscopic larva called a
planula, typically pink and elliptical in shape.
 A typical coral colony forms several thousand larvae per year to overcome the
odds against formation of a new colony.

16. Brooders
 Brooding species are most often ahermatypic (not reef- building) in areas of
high current or wave action.
 Brooders release only sperm, which is negatively buoyant, sinking on to the
waiting egg carriers who harbor unfertilized eggs for weeks.
 After fertilization, the corals release planula that are ready to settle.

18. Asexual reproduction
 In Asexual reproduction, new clonal polyps bud off from parent polyps to
expand or begin new colonies.
 This occurs when the parent polyp reaches a certain size and divides. This
process continues throughout the animal’s life.
 Within a coral head, the genetically identical polyps reproduce asexually,
either via gemmation (budding) or by longitudinal or transversal division.

19. Budding
 It involves splitting a smaller polyp from an adult.
 As the new polyp grows, it forms its body parts. The distance between the
new and adult polyps grows, and with it, the coenosarc (the common body
of the colony).
 Budding can be:
 Intratentacular—from its oral discs, producing same- sized polyps within the
ring of tentacles.
 Extratentacular—from its base, producing a smaller polyp.

20. Fission / Division
 Logitudinal division- It begins when a body broadens and then divides its
coelenteron, analogous to splitting a log along its length. The mouth also
divides and new tentacles form. The two “new" polyps then generate their
missing body parts and exoskeleton.
 Transversal division – occurs when polyps and the exoskeleton divide
transversally into two parts. This means one has the basal disc (bottom) and
the other has the oral disc (top), similar to cutting the end off a log.

21. Economic uses
 Ornamental
 Medicinal uses
 Construction of buildings
 Promote tourism
 Aquarium trade
 Aquaculture


22. Threats and present status
 All the coral species and endangered in IUCN REDLIST
 Coral reefs are under stress around the world.
 In particular, coral mining, agricultural and urban runoff, pollution
(organic and inorganic), overfishing, blast fishing, disease, and the
digging of canals and access into islands and bays are localized
threats to coral ecosystems.
 Broader threats are sea temperature rise, sea level rise all and pH
changes from ocean acidification, associated with greenhouse gas
emissions.
 In 1998, 16% of the world's reefs died as a result of increased water
temperature General estimates show approximately 10% of the
world's coral reefs are dead.

25. Reference

26. Thank you