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Porifera Notes

Porifera Notes. Wakefield 2011-2012. General Characteristics. Phylum Porifera means “pore-bearing” . Their sac-like bodies are perforated by many pores

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Porifera Notes

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  1. Porifera Notes Wakefield 2011-2012

  2. General Characteristics • Phylum Porifera means “pore-bearing”. Their sac-like bodies are perforated by many pores • As adults, all sponges are sessile although in their larval form they are motile. When sessile, they depend on water currents to bring them food and oxygen and remove waste products

  3. General Characteristics C. The sponge body is an efficient water filter. Some large sponges can filter 1500 liters each day

  4. General Characteristics D. There are approximately 8300 species of sponge . . . Most of these are marine a few live in brackish water and 150 species are freshwater

  5. General Characteristics • They have radial symmetry

  6. General Characteristics • Sponges are considered to be multi-cellular but they have no tissues or organs; each cell of their body functions somewhat independently • They have no senseorgans or nervous system

  7. General Characteristics H. Porifera have few predators. They have a foul taste and noxious odor and also have a defensive skeleton system

  8. General Characteristics • The Porifera phylum is very ancient with fossil records stretching back to the Cambrian epoch. 540-490 mya.

  9. General Characteristics • The skeletal structure of a sponge can be either fibrous or rigid or both. 1. the fibrous part is made up of a specialized collagen material called spongin

  10. General Characteristics 2. the rigid component of the sponge skeleton is made up of calcium carbonate (CaCO3) or silica (glass) spicules.

  11. General Characteristics 2. (con’t) These spicules may be needle like, star shaped or six-rayed and embedded in the spongin or the inter cellular matrix called the mesohyl (gelatinous layer) Siliceous Spicules

  12. General Characteristics • Living sponges are assigned to one of four classes Calcarea

  13. General Characteristics • Living sponges are assigned to one of four classes Hexactinellida

  14. General Characteristics • Living sponges are assigned to one of four classes Demospongiae

  15. General Characteristics • Living sponges are assigned to one of four classes Sclerospongiae

  16. General Characteristics 1. Taxonomists use the type of spicule as a classification tool a. Members of Class Calcarea have CaCO3 spicules with 2, 3, or 4 rays

  17. General Characteristics b. Class Hexactinellida sponges have 6-rayed siliceous spicules

  18. General Characteristics c. Class Demospongiae have glass spicules but not six-rayed, spongin only or both spicules and spongin depending on the species

  19. General Characteristics d. Class Sclerospongiae have massive CaCO3(calcareous) skeletons and siliceous spicules

  20. Form & Function • There are two types of body opening in sponges • Small incurrent pores are called ostia (ostium) • Large excurrent pores are called osculum

  21. Form & Function B. Inside the sponge body, water is directed past choanocyte cells where food & oxygen (O2) are collected. Choanocyte cells a.k.a. collar cells and have 2 main purposes

  22. Form & Function Choanocyte cells a.k.a. collar cells and have 2 main purposes – 1. they keep water flowing through the sponge by beating their flagella 2. they trap food particles passing by. (See pg 245 – figure 12-7 in text)

  23. Form & Function Sponges non-selectively phagocytize food particles between the sizes of .1 um and 50 um (with the majority being the smaller sizes) (um = micrometer) (see page 247 – figure 12-12 in text)

  24. Types of Canal Systems • Asconoid canal system is a flagellated spongocoel • Simplest for of canal system, sponges with this type of canal are small and tube-shaped

  25. Types of Canal Systems • Water flows through a large central space called the spongocoel (sponge body cavity) and it is lined with choanocyte cells. Flagella pull water through but much water flows through unfiltered • The only class of sponges that have asconoid canal systems are some of the calcerea

  26. Types of Canal Systems • Syconoid canal systems – flagellated canals • Sponges with this canal system are larger and thicker walled than the asconoids

  27. Types of Canal Systems • The body walls hold radial canals that are lined with the choanocyte cells so that water is filtered before it empties into the spongocoel • Syconoid canal systems are found in hexactinellida and demospongiae classes

  28. Types of Canal Systems • Leuconoid canal systems – flagellated chambers • These are the most complex types of sponges • Because they are more efficient at extracting food particles from water they can grow much larger. They have many oscula (excurrent canals)

  29. Types of Canal Systems c. Clusters of flagellated chambers are filled with choanocyte cells and they are filled from incurrent canals and discharge into excurrent canals

  30. Types of Canal Systems • Largest of all sponges have this canal system • It is found in all three classes 1. Calcarea 2. Demospongiae 3. Hexactinellida

  31. D. Types of Sponge Cells 1. Sponge cells are arranged in a gelatinous matrix called mesohyl ; this is the connective tissue of sponges

  32. D. Types of Sponge Cells • Because of the absence of true tissues, all fundamental processes must occur at the cellular level • The only visible movement in sponges is the closing and opening of the pores

  33. D. Types of Sponge Cells • Choanocytes are also called flagellated collar cells • One end is embedded in the mesohyl; this is called the cell body • The exposed end has a mucous membrane to collect food • A flagella which waves to trap food particles and create water currents

  34. D. Types of Sponge Cells • Archaeocytes are also called amoebocytes • They can move about in the mesohyl by psuedopods • They phagocytize food particles • They can repair wounds because they can differentiate into any type of cell needed by the sponge

  35. D. Types of Sponge Cells • They can become schlerocytes to secrete spicules • They can become spongocytes to secrete spongin • They can become pinacocytes to repair the pinacoderm • They can become collencytes to secrete collagen

  36. D. Types of Sponge Cells • Pinacocytes – flat epithelial cells a. Form the outer dermis of the sponge called the pinacoderm

  37. E. Regeneration • Sponges have great ability to regenerate lost parts and repair injuries • Sponge fragments have the ability to re-aggregate into new structures-this is called somatic embryogenesis; this process is largely due to the ability of the archaeocytes to differentiate into any type of sponge cell

  38. F. Reproduction • Asexual reproduction • Includes regeneration following fragmentation • Internal buds called gemmules to survive drought & freezing

  39. F. Reproduction C. External buds are small sponges that break off the adult after attaining a certain size (called budding)

  40. F. Reproduction • Sexual Reproduction (for most sponges) • Most sponges are monoecious with both male and female sex cells in one individual • Sperm are formed from transformed choanocytes and when mature they will release from the mesohyl and swim away using their flagella

  41. F. Reproduction c. When sperm are released from one sponge they may be inhaled into the incurrent ostia of an adjacent sponge • When a choanocyte’s flagella traps the sperm instead of digesting it, the choanocyte becomes fertilized and turned into a zygote • The archaeocytes provide nourishment until the zygote develops into a ciliated larvae and swims away out through the oscula

  42. F. Reproduction 3. Some sponges release both oocytes (eggs) and sperm out into the water and practice external fertilization http://www.youtube.com/watch?v=KOFFzXNYJG0&safety_mode=true&persist_safety_mode=1&safe=active

  43. Classes of Sponges • Class Calcarea • Calcareous sponges with spicules of CaCO3 • Spicules have straight or 3-4 rays • Most are small and tube or vase shaped • Some are bright red, yellow or purple • Found in shallow marine water habitats to 50 meters • Asconoid, Syconoid and Leuconoid canal forms

  44. B. Class Hexactinellida • Glass sponges with 6-rayed spicules made of silica • Deep sea forms to 500 meters • Root spicules attach them to the substrate • Their spicules form a latticework of fantastic shapes • Their fragile glass skeletons only allow them to live in the areas of calm and gently flowing water • Body design shows both syconoid and leuconoid canal forms

  45. C. Class Demospongiae • This class contains 95% of all living sponge species • This is the only class that has species without spicules at all. Some of the species only have skeletons made of spongin • If they do have spicules, they are of silica but are not 6-rayed • This is the only class with freshwater species the Spongillia freshwater sponges flourish in warm summer waters but die back in winter and leave gemmules, usually found in well-oxygenated ponds and streams • Commercial bath sponges are harvested from this class • All species of this class are leuconoid canal design

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