Lab 2 Phylum Porifera and phylum Cnidarias3.amazonaws.com/prealliance_oneclass_sample/KZWwYxWvlb.pdf · Lab 2 – Phylum Porifera and phylum Cnidaria Phylum Porifera Adults sessile

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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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