Coelenterata is a phylum of aquatic animals that includes jellyfish, corals, sea anemones and hydroids. They are diploblastic with two main cell layers, a gelatinous mesoglea in between, and stinging nematocysts. They exhibit radial or biradial symmetry and polymorphism. Reproduction can occur asexually through budding or sexually through external fertilization and a planula larva stage. The phylum is divided into three classes: Hydrozoa, Scyphozoa, and Anthozoa.

1. Coelenterata
Bollapalli Ashok Kumar
M.Sc.,B.Ed.,M.A(Lit)CSIR-NET,(Ph.D)
LECTURER IN ZOOLOGY
KRK Govt Degree & PG College
ADDANKI-523201
Phone:9652929696,9441635264
Email:
ashokkumarzoology@gmail.com

2.  9000 living sps and many fossils since Ordovician
period
 Marine , some are fresh watered
 Proterospongia-link between Protozoa and
Coelenterata
 Ctenoplana- link between Coelenterata and helminthes
 Cyanea arctica - Big and Long jelly fish-7.5.m radius
with 120 yards long tentacles
 Chirposalmus , Chironex jelly fishes are most
poisonous
 Coelenterates are called stinging animalcules
COELENTERATA

3.  PEYSONNEL (1773) called them as coral insects
 Linnaeus, Lamark ,Cuvier included these in Radiata
 Eschscholtz (1829) divided radiata into three groups like
Zoophyta, Ecalepha, Echinodermata. He studied
Ecalepha and later described Ctenophora and
Siphonophora medusae
 Johnston (1939) separated Hydroidea class
 Leuckart (1947)formed this phylum including sponges
and ctenophora
 Hatschek (1888) divided it into Spongiaria, Cnidaria ,
Ctenophora
COELENTERATA- Historical Background

4. Metazoan multicellular animals
Tissue grade of organisation
Aquatic animals except Hydra all are marine.
Solitary or Colonial, sedentary or free living
Radial or bilateral symmetry
Two types of individuals- polyp (asexual
form) and free swimming medusa (sexual
form)
General characters- Coelenterata

5. Zooids - small animals in a colony .
Depending on function, the nature of
zooid changes thus shows polymorphism
Diploblastic body wall with two cellular
layers
1. Outer epidermis
2. Inner gastrodermis
3. Gelatinous mesoglea in between
Body layers are with special nematocysts –
more in tentacles- many types. Stinging
cells useful for killing and protection
General characters- Coelenterata

6.  Acoelomate organisms
 Digestive system is incomplete anus being
absent and mouth for ingestion and egetion.
Digestion is intra and extracellular
 Mouth is with small, thin tentacles which are
useful for food capture, ingestion, locomotion
and protection
 Gastro vascular cavity is often branched. It
opens outside through mouth
General characters- Coelenterata

7.  Respiratory , circulatory and excretory systems
are absent
 Muscular system of epithelio and endothelio
muscle cells is present. Independent fibres are
present in mesoglea.
 Nerve nets of synaptic or non synaptic pattern
with diffuse conduction
 Sense organs are simple or complicated. Some
are with ocellli and statocysts
General characters- Coelenterata

8. Asexual reproduction – budding/binary
fission
Sexual reproduction by gametes. Sexual
forms are monoecious or dioecious
Development exhibits planula larva
Life cycle is with alternation of
generations with polyp generation and
medusoid generation
General characters- Coelenterata

9. HYDROZOA
SCHYPHOZOA
ANTHOZOA
Classification- Coelenterata

10.  Solitary/ colonial, polyp and medusoid forms
 Radial symmetry
 Body wall –ectodermis,mesoglea and gastrodermis
 Gastrocoel is spacious
 Cnidoblasts are absent
 Body has thick perisarc.in some animals this is very solid and called
coral
 Polymorphism is seen
 Alternation of generation
 Sex cells are formed from ectoderm
 Fertilization is external
 Holoblastic cleavage
 Planula larva
 2700 genera included
 Five orders
 Ex: Hydra,Bougainvillea,Millipora,Physalia,Velella,Porpita,Helistemma
HYDROZOA

12.  Solitary, medusoid
 Medusa umbrella or bell shaped with/without stalk
 Gastrocoel has gastro fibres, Gonads and bifurcated into four radial
septa. With tetra radial symmetry
 umbrella structure is with more mesoglea
 True velum is wanting.
 Animal end is with lappets
 Exumbrellar surface has median manubrium
 Sex cells derive from gastro dermis and release gametes into
gastrocoel
 Monoecious
 200 genera included
 Five orders included
 Rhizostoma, Aurelia, Periphylla, Cassiopea, Lucernaria, Charybdea,
Pericolpa, Tomoya
SCHYPHOZOA

14.  Solitary/colonial, polypoid marine forms
 Hexamerous , octamerous ,polymerous, biradial or radio-bilateral
symmetric animals
 Anterior region becomes wide to form oral disc to accommodate
tentacles
 Mesoglea with tissue
 Gastrocoel has septa formed by mesenteries
 Epidermis secretes test of CaCo3 or horny material
 Inner side of mesentery has cnidoblasts
 Gonads derive from gastrodermis and developed from mesentery.
Gametes are released into gastrocoel
 Fertilisation is external. Life cycle includes planula
 It inncludes 6100 genera
 2 sub classes and eleven orders
 Pennatula, Metridium, Fungia ,Adamsia, Madripora, Meandrina,
Gorgonia, Alcyonium, Tubipora, Heliopora
ANTHOZOA