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Lab 2 – Phylum Porifera and phylum Cnidaria
Phylum Porifera
Adults sessile and attached
Radial symmetry or asymmetrical
Multi-cellular ; loose aggregation of cells
Skeleton made of collagen and spicules (calcareous or siliceous)
No organs or true tissue
Specialized for filter-feeding
Digestion is intracellular (no mouth , anus or digestive system)
Excretion and respiration by diffusion
No nervous system
Asexual (budding or formation of gem mules)
Sexual (eggs and sperm produce ciliated larvae)
Dioecious
Mostly marine; few are freshwater
Grantia
Kingdom :- Animalia
Phylum:- Porifera
Class:- Calcarea
Order:- Leucosolenida
Genus:- Grantia
Tubular or syconoid-shaped
Water enters via small pores (incurrent pores)and exists via large pore (osculum)
Outer surface covered in flat cells (pinacocytes),inner choanocyte layer and the
middle is mesohyl (gelatinous protein matrix)
Pinacocoytes at base of sponge secrete a substance that attached sponge to its
substrate
Water flow;incurrent pores> incurrent canals >radial canal (flagellated
choanocytes)>central cavity/spongocoel > osculum
Choanocytes –generate feeding current
Skeletal components (non-living)-spongin fibers,spicules of calcium
carbonate/silicon dioxide.
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Phylum Cnidaria
Sedentary or free-swimming metazoan
Radial symmetry
Body wall composed of two cell layers;
o Outer ectoderm
o Inner endoderm
o Structure-less layer between them(mesoglea)- contains cells derived from primary cells
Nervous system is a network of cells
No specialized organs for excretion(its by diffusion)
Asexual (budding)
Sexual (planula larva- ovoidal and uniformlyciliated is produced)
2 body forms (polyp or medusa)
Nematocysts (stinging threads)- for capturing prey
Class Hydrozoa :-Polyp and medusoid body forms occur in successive stages of life cycle
-polyps(colonies) have 2 types ;gastrozooids(feeding) and gonozooids
(asexual reproduction)
- Medusoid – reproduces sexually to produce a planula larva
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Order Hydroida : well developed polyploidy generation.(solitary or colonial).
Usually buds off as free medusa. Eg. Hydra (solitary with no medusoid stage ),
Velella and Porpita(free-floating polymorphic colonies), Obelia
Order Siphonophora:- swimming colonies. Consisting of many kinds of polyp
and medusae (polymorphic).medusae attached to stem. marine. Eg. Physalia
(Portuguese man of war).
Class Scyphozoa :- Medusoid stage as main stage of life-cycle
-polypoid form only in larva.
-Eg. Aurelia (common jelly-fish)
Class Anthozoa:- corals, sea anemones
- attached polyps
- NO medusa
- Some members posses a skeleton
-gonads found in septa
- all marine
- Soliatry or colonial
-Eg. Gorgonia (sea fan), Pennatual (feather-like sea pen), Metridium (sea
anemone with no skeleton), Meandria (brain coral with big external calcareous
skeleton)
Hydra
Kingdom :- animalia
Phylum:- Cnidaria
Class:- Hydrozoa
Order:- Hydroida- Anthomedusa
Genus:- Pelmatohydra (brown hydra)
Batteries of intact nematocytes are located in cnidocyte
Epidermis of hydra possesses epitheliomuscle cells and interstitial cells
Gastrodermis possesses flagellated nutritive muscle cell and gland cells
Food vacuoles are present in gastrodermal cells
Space in the centre of the cross section is the gastrovascular cavity (enteron)
Mesoglea – thin layer between epidermis and gastrodermis
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Obelia
Kingdom :- animalia
Phylum:- Cnidaria
Class:- Hydrozoa
Order:- Hydroida- leptomoedusae
Genus:- Obelia
Gastrozooid (feeding polyp)- comprises the tentacles,mouth and hypostome
Chitinous sheath covers the living tissue of the central stalk and branches and extends
over the base of the polyps
Gonozooid (reproductive polyp)
Obelia medusa is bell-shaped
Ventral surface of bell has manubrium that hangs from centre and contains the
mouth
Mouth leadsto 4 radial canals and ring canal(circles the margin of the bell and
connects with the hollow tentacles)
Canals are lines with gastrodermal cells (intracellular digestion occurs)
Statocysts (balancing organs)- found between tentacles
Mesoglea is thick in all medusa and takes up the volume of organism
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Mature gonads are noticeable (4 dark structures in the region of the radial
canals)
Alteration between sexual and asexual generations is call metagenisis
Obelia life-cycle
The polyp colony reproduces asexually.
During this stage of life, Obelia are confined to substrate surfaces.
On this mature colony there are individual hydranths called gastrozooids, which can be
found expanded or contracted, to aid in the growth of this organism by feeding;
the reproductive polyp gonozooids has medusa buds. Other hydranths are specialized
for defense.
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The next generation of the life cycle begins when the medusae are released from these
gonozooids, producing free swimming only male medusae velum with gonads, a mouth,
and tentacles.
The physical appearance of the male and female medusae velum, including their
gonads, are indistinguishable, and the sex can only be determined by observing the
inside of the gonads, which will either contain sperm or eggs.
The medusae reproduce sexually, releasing sperm and eggs that fertilize to form a
zygote, which later morphs into a blastula, then a ciliated swimming larva called a
planula.
The planulae live free-swimming for a while but eventually attach themselves to some
solid surface, where they begin their reproductive phase of life.
Once attached to a substrate, a planula quickly develops into one feeding polyp. As the
polyp grows, it begins developing branches of other feeding individuals, thus forming a
new generation of polyps by asexual budding.
Why does Obelia represent a more “typical”
cnidarian than Hydra?
The "typical" Cnidarian life cycle has
two stages: one as a medusa (like a
jellyfish), the other as a polyp (like
Hydra). Obelia goes through both
stages, but Hydra does not have a
medusa stage.
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Aurelia (true jellyfish)
Kingdom :- animalia
Phylum:- Cnidaria
Class:- Scyohozoa
Order:- Semaeostomeae
Genus:- Aurelia
Horseshoe-shaped gonads are contained inside gastric pouches
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Metridium (sea anemone)
Kingdom :- animalia
Phylum:- Cnidaria
Class:- Anthozoa-Hexacorallia
Order:- Actiniaria
Genus:- Metridium
Animal rests of pedal disc
Has stout polyp form with tentacles surrounding the mouth
Thick body wall – because of mesoglea
Pharynx has ciliated tracts (siphonoglyphs)
Space below pharynx is gastrovascular cavity- 6 septa project here
Gonads resemble a string of beads along the free edge of each septum
No anus in all cnidarians (all undigested food exists via mouth)
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