Sponges, Phylum Porifera Chapter 6, Zoology

1. Sponges, Phylum Porifera Chapter 6, Zoology

2. Phylum Porifera • Pronounced (po-rif'-er-a) • The name means “bearing pores” • Sponges are made up of a system of tiny pores and canals that make up a intricate filter feeding system. • Sponges are sessile, meaning they have a stationary, inactive lifestyle. • Their bodies are made up of thousands of cells mixed together in a gel-like mixture, supported by small structures called spicules made of calcium carbonate or silica and collagen.

3. Phylum Porifera • Because they are sessile, they are highly dependent on ocean currents to bring food to them and eliminate waste products. • They have no organs or true tissues. • Digestion is intracellular. Respiration and excretion occurs by simple diffusion. No nervous system. • Sponges are asymmetrical. • There are three main classes of sponges; Calcarea, Hexactinellida, and Demospongiae.

4. Sponge Ecology • There are about 5000 sponge species. • About 97% are marine, 3% freshwater. • Embryos are free-swimming. • Adults are always attached to other objects. (rocks, corals, submerged objects etc.) • Many other organisms such as crab and fishlive symbiotically in or on sponges. • Some sponges live on other organisms like molluscs and corals.

5. Diversity of Sponges

6. Sponge Anatomy and Physiology • Their bodies are made of numerous tiny pores called Ostia that allow water to flow into a sponge. • One to several large openings that allow water to flow out of a sponge are called Oscula. • A singular Oscula is called an Osculum. • Small cells that line the canals of a sponge with whiplike flagella are called Choanocytes. • The flagella on the choanocytes maintain the flow of water through the canals. • The choanocytes also trap food particles.

7. Sponge Anatomy and Physiology

8. Sponge Canal Systems • Sponges have three types of canal systems; Asconoid, Syconoid, and Leuconoid.

9. Sponge Canal Systems

10. Asconoid Sponges(Flagellated Spongocoels) • Asconoids have the simplest body plan of the sponges. They are small and tube shaped. • Water enters the ostia into a large cavity called the Spongocoel. • The choanocytes then expel the water out the osculum. • Asconoids are found only in the class Calcarea.

11. Asconoid Sponges(Leucosolenia sp.)

12. Syconoid Sponges(Flagellated Canals) • Similar to Asconoids. Water is expelled through one large osculum like in the asconoids. • Choanocytes do not line the spongocoel. • The choanocytes line individual canals along the sides of the body tube called radial canals. • Syconoids are mostly found in class Calcarea. • Some are also found in class Hexactinellida

13. Syconoid Sponges(Sycon sp.)

14. Leuconoid Sponges(Flagellated Chambers) • The Leuconoid body plan is the most complex. • Their unique body design allows for a much greater body size. The increased body size increases the amount of flagellated choanocytes, therefore increasing the amount of food that can be consumed. • Most leuconoids are large masses rather than simple tubes, with numerous oscula. • There is no spongocoel in leuconoids. • They are found in all three classes of sponge.

15. Leuconoid Sponges

16. Cellular Structure of Sponges • The connective tissue of sponges consists of a loose gel-like mixture called Mesohyl. • The epithelial cells of sponges are called Pinacocytes. These cells play a role in trapping food particles. • Porocytes make up the ostia that allow the passage of water into the sponge. • Archaeocytes are cells in the mesohyl that perform a variety of functions such as digestion and production of spicules and collagen.

17. Cellular Structure of a Sponge

18. Sponge Skeletons • An important structural protein in the animal kingdom and in sponges is called collagen. • Thin strands of collagen are found throughout the bodies of sponges. • The class of Demospongiae produces a form of collagen known as spongin. • Various forms of spicules are found throughout the different classes of sponges. They are made up of Silica or Calcium Carbonate.

19. Sponge Skeleton • Spicules on the left • Spongin on the right

20. Sponge Metabolism • As mentioned earlier, various sponge cells such as choanocytes and pinacocytes aid in digestion by trapping food particles. • The primary cell type that actually metabolizes the food are the archeocytes. • Respiration and excretion occur by diffusion. • All metabolic activities are highly dependent on a constant flow of water from ocean currents. • Some sponges filter as much as 1500 liters/day!

21. Sponge Digestion

22. Sponge Reproduction • Sponges reproduce both sexually and asexually. • Most sponges are monoecious. Meaning a single sponge can have both male and female sex cells. • Sperm cells develop from choanocytes. Egg cells can develop from choanocytes in some species and from archaeocytes in others.

23. Sponge Reproduction • After fertilization, the zygotes develop into a free-swimming flagellated larva called a parenchymula. • Paranchymula break off from the adult sponge and are carried away by ocean currents. • Sponges can reproduce asexually by fragmentation (this occurs when a fragment is broken off from the main body of the sponge) and by external budding. • Budding occurs when a small sponge grows off of the adult sponge. Eventually these can break off and regenerate.

24. Sponge Reproduction • Asexual reproduction can also occur by the formation of internal buds called gemmules. • Gemmules are internal buds that are usually dormant and contain archaeocytes. • Gemmules are formed during unfavorable conditions like drought, freezing temperatures, and anoxia for long periods of time. • After the unfavorable conditions pass, the archaeocytes can then be released from the gemmules to regenerate into a new sponge.

25. Sponge Larva and Gemmules • Parenchymula on the right. • Gemmule on the left

26. Class Calcarea • Spicules of calcium carbonate (calcite and limestone) • All three types of canals represented (asconoid, syconoid, and leuconoid). • All marine (Clathrina) Class Calcarea

27. Class Hexactinellida • Six-rayed spicules made of silica (same substance as glass) • Body often cylindrical and funnel shaped • Syconoid or leuconoid • All Marine Venus Flower Basket (Euplectella)

28. Class Demospongiae • Skeleton made of silica spicules that are not six-rayed, or a skeleton made of spongin, or both. • Leuconoid type canal systems only. • One family freshwater,all others are marine. Very diverse group of sponges