1. Phylum Porifera - Sponges
Kingdom Animalia
Phylum Porifera - Sponges

2. Introduction
They are considered animals because they are multicellular, heterotrophic and their cells have no cell walls
Less than 2% of species are found in freshwater
Are sessile – remain attached to the substrate
Are most remarkable for the characteristics they lack than for those they possess
Lack a nervous system and have no true musculature
Have no organs (digestive, reproductive, respiratory, sensory or excretory)
Are amorphous (asymmetrical)
Do not have anything corresponding to an anterior, posterior or oral surface

3. Structure
In its simplest form, the typical sponge is a fairly rigid perforated bag whose inner surface is lined with flagellated cells
2 cell layers: (not tissues)
Epidermis: A contractile cell layer that allows the sponge to undergo minor shape changes
Inner Cell Lining: Composed of choanocytes or collar cells

7. Evolutionary side bar
Choanoflagellates are unicellular organisms that will live in colonies
It is hypothesized that they will share a common ancestor with sponges

8. RELATIVES Recent studies suggest that choanoflagellates are cousins to all animals in the same way that chimpanzees are cousins to humans. From left, a choanoflagellate colony, feeding cells of sponges that resemble choanoflagellates and a choanoflagellate with its long flagellum and collar of filaments. There can be millions of choanoflagellates in a gallon of sea water. Credit Left and Right, Mark Dayel, Center: Scott Nichols

9. Structure
These two cell layers sandwich a middle, jelly-like mesoglea which contains amoeboid-like cells called amoebocytes which perform MANY functions for the sponge
This layer also contains support elements called spicules

10. Spicules - A needlelike structure made of silica or calcium carbonate that, in large numbers, makes up the supporting framework of various sponges.

11. Cell Types
Ectoderm - Contractile cells that allow for minor shape changes
Choanocytes/collar cells - The collars of sponge choanocytes are almost certainly homologous with those of choanoflagellates
Amoebocytes – wander through the mesoglea and perform a number of essential functions
Porocytes – Allow water to flow from surrounding environment to the inside of the sponge

13. Functions of Choanocytes
To generate currents that help maintain circulation of seawater within and through the sponge
To capture small food particles
To capture incoming sperm for fertilization

14. Functions of Amoebocytes
Digest food captured by choanocytes
Store digested food
Give rise to both sperm and egg cells
Play a role in eliminating wastes
Specialized cells secrete the supporting elements located in the mesogleal layer (spicules)
Produce dormant structures called gemmules in freshwater species when conditions are unfavourable

15. Locomotion
Adults are sessile
Larva = mobile

16. Ingestion, Digestion and Elimination
Sponges filter the water they pass through themselves for phytoplankton and zooplankton:
Collar cells beat flagella creating a current bringing in water through ostia
Mucus on the collars trap food where it is ingested by endocytosis
Some of the food is digested within food vacuoles in the choanocytes, some is transferred to the amoebocytes

18. Ingestion, Digestion and Elimination
Amoebocytes transport nutrients to other cells of the body
Waste materials are enclosed in a waste vacuole and leave the cell body (they are then eliminated into the spongocoel, where they leave the sponge
Excretion consists of the diffusion of nitrogenous wastes out of the cells

19. Respiration
Respiration is through direct diffusion (Remember, no organs!!!!)
Oxygen diffuses from the water into the cells
Carbon dioxide difuses from the cells to the water

20. Reproduction Asexual By fragmentation or budding
Freshwater species produce gemmules (These have the same function as endospores in bacteria)
Gemmules are a clump of spicules and food-laden amoebocytes covered in a tough protective coat
Gemmules of some species have hatched successfully after 25 years of storage

21. Reproduction Sexual Some species of sponges have separate sexes
Other sponges have both sexes and are hermaphrodites
Sperm and egg are produced by the amoebocytes
Sperm are released out of the osculum and are carried by water current to other sponges, where they enter the ostia and are caught by choanocytes
The sperm are transferred to the amoeboid egg cell where they are fertilized internally
Zygotes develop into flagellated larvae which break loose and are dispersed by the water currents

24. Ecological Importance
Provide habitats for other animals (eg. Snails, sea stars, shrimp, rockfish

25. Ecological Importance
Are a source of food for other animals (snails and small fish)
Provide camouflage for small animals (Decorator crabs often have sponges growing on their shells)
Many species are involved in symbiotic relationships with photosynthetic organisms

26. The Sponge Decorator Crab

27. Ecological Importance
Help clean up the ocean floor by boring into dead shells and corals, releasing chemicals to break them down

28. Economic Importance
Used commercially for bathing/cleaning sponges (although artificial sponges have replaced the need for a large fishery)
Many sponges produce toxins as a defense against predators. These toxins are used in cancer and viral research, along with antibiotic research