Porifera

Porifera, commonly known as sponges, are simple, multicellular organisms found primarily in marine environments. Characterized by their porous bodies and lack of true tissues and organs, sponges filter water to obtain food and oxygen. They play a crucial role in aquatic ecosystem by maintaining water quality and providing habitat for other species. With their unique cellular structure and ability to regenerate, Porifera offer valuable insights into early animal evolution and developmental biology.

What is Porifera?

Porifera, or sponges, are simple, multicellular organisms lacking true tissues and organs. Found mainly in marine environments, they filter water through their porous bodies for nutrition and respiration, playing a vital role in aquatic ecosystems and offering insights into early animal evolution.

Examples of Porifera

1. Euplectella (Venus’ flower basket)
2. Spongilla (Freshwater sponge)
3. Sycon (Calcareous sponge)
4. Haliclona
5. Cliona
6. Aplysina (Stove-pipe sponge)
7. Geodia
8. Oscarella
9. Axinella
10. Chondrilla (Chicken liver sponge)
11. Tethya (Golf ball sponge)
12. Cinachyra
13. Callyspongia (Tube sponge)
14. Ircinia (Bath sponge)
15. Mycale
16. Petrosia
17. Dysidea
18. Phakellia

Porifera Species

1. Simple Animals: Multicellular but basic in structure, sponges (Porifera) are fascinating organisms, often compared to renewable resources for their ability to regenerate and sustain their populations.
2. Porous Bodies: Characterized by many pores.
3. No True Tissues: Sponges lack distinct tissue layers, while Cnidaria possess true tissues like epidermis and gastrodermis.
4. Sessile Lifestyle: Porifera and Cnidaria are often attached to surfaces like rocks, coral, and other substrates.
5. Filter Feeders: Extract nutrients from water.
6. Aquatic Habitats: Found in marine and freshwater environments, sponges (Porifera) and Cnidaria exhibit diverse forms of autotrophs and other feeding mechanisms.
7. Spicules: Have structural support elements.
8. Examples: Includes sponges like Demospongiae and Calcarea.

Porifera Classification

1. Class Calcarea: Marine sponges with calcium carbonate spicules.
2. Class Demospongiae: Largest class, includes sponges with siliceous spicules or spongin fibers.
3. Class Hexactinellida: Glass sponges with six-rayed siliceous spicules.
4. Class Homoscleromorpha: Enigmatic sponges with simple spicules or none at all.

Porifera Characteristics

1. Multicellular: Composed of many cells.
2. Porous Bodies: Have numerous pores (ostia).
3. No True Tissues: Lack distinct tissues and organs.
4. Sessile: Attached to surfaces, immobile.
5. Filter Feeders: Draw water through pores to filter out food particles.
6. Simple Body Structure: Composed of three layers – epidermis, mesohyl, and choanocytes – lacking voluntary muscles.
7. Asexual and Sexual Reproduction: Can reproduce by budding, fragmentation, or producing gametes.
8. Spicules: Provide structural support, made of silica or calcium carbonate.

Porifera Habitat

1. Marine Environments: Predominantly found in oceans.
2. Freshwater Habitats: Some species inhabit rivers, lakes, and streams, adapting their breathing to various aquatic environments.
3. Shallow Waters: Common in coastal areas and coral reefs.
4. Deep Sea: Present in deep ocean trenches.
5. Substrate Attachment: Attach to rocks, coral, and other hard surfaces.
6. Symbiotic Relationships: Often host microorganisms like algae.
7. Varied Depths: Found from intertidal zones to depths of several thousand meters.
8. Stable Environments: Prefer environments with stable conditions for growth.

How Do Porifera Reproduce

1. Asexual Reproduction:
   • Budding: Small buds form and detach to grow into new sponges.
   • Fragmentation: Pieces of the sponge break off and develop into new individuals.
   • Gemmules: Internal buds called gemmules form, survive harsh conditions, and grow into new sponges.
2. Sexual Reproduction:
   • Hermaphroditic: Most sponges produce both eggs and sperm.
   • Sperm Release: Sperm is released into the water through the osculum.
   • Internal Fertilization: Sperm is captured by another sponge and transported to the egg inside the body.
   • Larval Stage: Fertilized eggs develop into free-swimming larvae.
   • Settlement: Larvae settle on a surface and grow into adult sponges.

What are the 3 body forms of Porifera?

1. Asconoid:
   • Simplest Structure: Tube-like shape.
   • Central Spongocoel: Single large cavity lined with choanocytes.
   • Small Size: Limited surface area for feeding.
2. Syconoid:
   • Folded Body Wall: Increases surface area.
   • Radial Canals: Choanocyte-lined canals that lead to the central spongocoel.
   • Intermediate Complexity: Larger and more efficient than asconoids.
3. Leuconoid:
   • Most Complex Structure: Extensive canal system.
   • Clusters of Chambers: Choanocyte-lined chambers instead of a central spongocoel.
   • Large Size and Efficiency: Most common and largest body form, maximizing feeding efficiency.

Differences Between Sponges (Porifera) and Cnidaria

Characteristic	Sponges (Porifera)	Cnidaria
Body Structure	Simple, porous bodies	Radially symmetrical bodies
Tissue Organization	Lack true tissues and organs	Have true tissues (epidermis, gastrodermis)
Feeding Mechanism	Filter feeders using choanocytes	Predators using tentacles with cnidocytes
Reproduction	Asexual (budding, fragmentation, gemmules) and sexual	Asexual (budding) and sexual
Movement	Sessile (immobile)	Sessile (polyps) and free-swimming (medusae)
Examples	Sponges like Demospongiae and Calcarea	Jellyfish, sea anemones, corals