Sponges are multi-cellular aquatic animals that live fixed to the sea floor and filter feed. They come in about 9,000 species divided into three main classes based on their skeleton composition. Sponges lack true tissues and organs. They are composed of three main cell types - pinacocytes, choanocytes, and mesenchyme cells. Choanocytes generate water currents that both capture food and circulate water through the sponge. Sponges reproduce sexually through internal fertilization and larval development or asexually by fragmentation.

1. Phylum Porifera
The Sponges

2. • Commonly known as sponges.
• ~ 9,000 species
• They are pore-bearing multi-cellular animals.
• lack germ layer.
• No internal organs.
• No muscles.
• Sessile, fixed, immobile.
• Asymmetric.

3. Three types of cells involved in sponge
formation
1. Pinacocytes.
2. Choanocytes.
3. Mesenchyme.
1. Pinacocytes:
• Will form pinacoderm.
• Some specialized as porocytes, and regulate
water circulation.

5. 2. Choanocytes:
• Will form inner layer choanoderm.
• They are flagellated collar cells.
• Flagellum and collar together, are used to gather
food.

6. Nucleus

7. 3. Mesenchyme cells:
• These cells specialized to perform function
in:
1. Reporoduction.
2. Transport.
3. Storing food.

8. Sponge Structure
• Simple in structure.
• One end attach to solid substratum.
• Other end has opening, Osculum.
• Ostia present over the body surface.
• Outer layer is pinacoderm.
• Inner layer is choanoderm.
• Between them is mesohyl.
• Large internal cavity is spongocoel.

9. Sponges have skeleton.
Two main component of skeleton:
1. Spongin: a proteinecious fibrous network.
2. Spicules: Needle-like spikes of silicon or
cacium carbonate.
• Provide support to sponge

11. Water Canal System
Essential element of water current system are:
1. Choanocytes/collar cells:
• Generate water current.
• Capture food particals and carry oxygen.
2. Osculum:
• An opening through which water is expelled.

12. Three types of sponge body form are described
based on the arrangement of water-current
system:
1. Ascon.
2. Sycon.
3. Leucon.

13. Ascon
Ascon sponges have very simple canal system.
• Vase-like shape.
• Water enter through ostia
• Lead to large internal cavity spongocoel.
• Expelled through osculum.

14. Sycon
• Osculum and spongocoel present.
• Body wall invaginations are incurrent canal.
• Incurrent canals have dermal pores.
• Pores connect incurrent canal to radial canal.
• Water enter through pores of incurrent and radial
canal into the spongocoel and expelled through
osculum.

15. Leucon
• Complex water current system.
• Have extensively branched canal system.
• Incurrent canal branching will form
choanocytes chamber.
• Canal carrying water away from chambers are
excurrent canals.
• Spongocoel absent.
• Multiple osculum.

18. • Sponges consume bacteria or small prey.
• Choanosytes sweep and filter suspended food
particles.
• Digestion begins in food vacuole.
• Partially digested food pass to mesohyl for
distribution.
• Pinacocytes phagocytize large food particle.
• Gas exchange and nitrogenous waste remove
by diffusion.
Feeding

20. Reproduction
Reproduce by sexual and asexual manner.
Sexual Reproduction:
• Hermaphrodite animals.
• Protogynous/Protandrous
• Avoid self-fertilization.
• Choanocytes will form sperms and eggs.
• Sperm released through osculum.

21. • Sperm from one sponge enter the body of
another sperm and trapped by choanocytes.
• After fertilization zygote will form.
• Early development lead to formation of
flagellated larva.
• Larva moves out from parent sponge.
• Attach to substratum and develop into new
adult.

23. Asexual Reproduction:
• Sponges reproduced asexually by
gemmulation.
• Mesenchyme cells enclosed themselves in
protective capsule to overcome adverse
condition.
• Capsule expelled from parent sponge.
• Under favorable conditions, cells comes out
from capsule by micropyle.
• Organize themselves into new sponge.

25. Classification
1. Class Calcarea:
• Calcareous sponges.
• Spicules made of calcium
carbonate.
• They are tubular.
• Body form may be ascon,
sycon or leucon.

26. 2. Class Hexactinellida:
• Commonly known as glass sponges.
• Spicules bound in glass-like lattice.
• They are siliceous.
• Body form may be sycon or leucon.
3. Class Demospongia:
• They have spicules and spongin.
• Spicules are siliceous.
• Body form is leucon.

27. Glass Sponge

28. Demosponge