1. Phylum Porifera

2. Porifera Characteristics
Freshwater and marine
Simplest of all animals
Asymmetrical
No systems for repro, digestion, respiration, sensory, excretion

3. Porifera Characteristics
~ 5,500 extant species
Highest abundance in unpolluted littoral and tropical reefs
~ 75% benthic biomass

4. Porifera Characteristics
Sessile (Adults)
Suspension-feeders (Adults)
Multicellular
Flagellated cells = choanocytes circulate water through water canals
No tissues
Cells totipotent

5. Porifera Characteristics
Outer and inner cell layers lack basement membrane
Middle layer (mesohyl) has motile cells and skeletal material
Skeletal elements (when present) are calcium carbonate, silicon dioxide and/or collagen fibers

6. Taxonomy and classification
Taxonomy based on skeletal elements
Now embryological, biochemical, histological, and cytological methods to diagnose sponge taxa

7. Three classes (Calcarea, Demospongiae, Hexactinellida)
Class Calcarea: Calcareous sponges
Shallow, tropical water, near shore
Leucetta

8. Class Calcarea Spicules = calcium carbonate
Calcarean spicules lack hollow canals = strong
Clathrina

9. Class Hexactinellida (Glass sponges)
Silica spicules
Spicules join at right angles, sponge appears artificial

10. Class Demospongiae (Demosponges)
Largest and most diverse class of sponges, ~ 90 percent of sponges
Spicules either spongin, an organic substance; or silica, a mineralized substance
Oscarella

11. Class Demospongiae
Genera Adocia, Halisarca, Myxilla

12. Aquiferous system Brings water to cells
1 x 10 cm sponge pumps 22.5 l water daily
Large sponge filters body mass every s

13. Sponges are single individuals
Grow by continually adding cells that differentiate as needed

14. Body structure and aquiferous System
Outer layer
Perforated by small holes - dermal pores or ostia
Choanoderm: innermost layer of flagellated cells = choanocytes
Mesohyl: middle layer

15. Body structure: 3 shapes

16. Asconoid sponges
Asconoid: one-cell thick choanoderm is simple and continuous
~10 cm height
Thin walls enclose central cavity; atrium opens outside via osculum
Pinacoderm has specialized cells; porocytes
External opening of porocyte canal is ostium or incurrent pore

17. Asconoid sponges

18. Syconoid sponges Syconoid: choanoderm folded Mesohyl two layers thick:
Outer region is cortex (contains skeletal material)

19. Leuconoid Sponge
Leuconoid: choanoderm subdivided into separate flagellated chambers

21. Flow rate Flow rate not uniform throughout
Water must move slowly over choanoderm
Exchange nutrients, gases, and wastes
Water leaving osculum must be carried far enough away to prevent fouling

22. Cells that line surfaces
Pinacocytes
Porocytes
Choanocytes

23. Cells that line surfaces
Porocytes
Form ostia
Cylindrical tube-like cells
Contractile - open and close pore to regulate diameter

24. Cells that line the surface
Choanocytes
= choanoderm
Create currents
Not coordinated in movement

25. Cells that secrete skeleton
Fibrillar collagen
Collencytes
Lophocytes
Spongocytes
Calcareous and siliceous spicules
Sclerocytes

26. Contractile cells Myocytes Contractile cells
Filament arrangement homologous with smooth muscle cell
Unlike neurons and true muscle fibers

27. Cell Aggregation Atlantic sponge (Microciona prolifera)
Pieces pressed through fine cloth
Separated cells reorganize
2-3 weeks
Self-recognition

28. Support Skeletal elements
Organic - collagenous
Inorganic – siliceous (hydrate silicon dioxide)
Sponges only animals that use hydrated silica as skeletal material

29. Sponge Harvest Harvested for thousands of years
Greeks harvested sponges
Sponge fishery south of FL, Bahamas, Mediterranean
1938: 2.6 million lbs

30. Sponge Harvest
Hippospongia
Spongia

31. Spicules Microscleres Megascleres
Demosponges and Hexactinellids have both
Calcareous sponges have only megascleres

32. Nutrition, Excretion, and Gas Exchange
Intracellular digestion
Continuously circulate water
Size selective feeders
Food capture
Phagocytosis and pinocytosis

33. Excretion
Ammonia and gas exchange
Diffusion

34. Activity and Sensitivity
Respond to environmental stimuli:
Close ostia or oscula, canal constriction, backflow

35. Reproduction and Development
Sexual and asexual reproduction
All sponges capable of sexual and asexual repro
Processes unknown due to lack of distinct, localized gonads (gametes, embryos occur throughout mesohyl)
Asynchrony of reproductive activity w/in populations

36. Reproduction and Development
Asexual Reproduction
All sponges produce viable adults from fragments
Cellular reorganization “pinches off” branch ends which regenerate into new adults – branching species

37. Reproduction and Development
Asexual Reproduction
Common in Florida’s sponge farms - cuttings attached to cement structure
Other processes include formation of gemmules, budding

38. Reproduction and Development
Gemmules
Produced in winter as dormant bodies
Coat and supportive cells protects from freezing and desiccation

39. Reproduction and Development
Gemmules

40. Reproduction and Development
Budding
Squat or elongate club-shaped protrusions from sponge surface
Buds drop, carried by current, adhere to substratum
Marine species

41. Reproduction and Development
Sexual Processes
Majority are hermaphroditic; produce sperm and eggs at different times
= Sequential hermaphroditism
Protogyny or protandry may occur once or many times during life

42. Reproduction and Development
Sexual reproduction
Sperm from choanocytes; eggs from choanocytes and archaeocytes

43. Reproduction and Development
Sexual process (Demospongiae and Calcarea)
Sperm and oocytes released into environment via aquiferous system
Sperm release -”smoking sponges”
Fertilization in open water (oviparous)
Few viviparous: sperm into nearby sponge’s aquiferous system; sperm to oocyte for fertilization

44. Reproduction and Development
Madsen sponge releasing sperm

45. Reproduction and Development
Release of larvae (vivipary)
Through aquiferous system or ruptured wall
Larvae swim hours or days, or crawl along substratum before settling
Larvae are lecithotrophic = use stored yolk

46. Reproduction and Development
Larval development

47. Distribution and Ecology
Calcareous sponges abundant in shallow waters < 200 m
Hexactinellids deeper
Demosponges at all depths

48. Distribution and Ecology
Sensitive to suspended sediments
Resistant to hydrocarbon and heavy metal contamination
Why?

49. Symbioses Commensalism common (small inverts, fishes)
Protection, habitat, water currents for suspended food particles
Some organisms utilize sponge for camouflage, small piece on shell or carapace

50. Boring Demosponges - harmful to corals and mollusc shells
= bioerosion; chemical and mechanical removal of fragments by etching cells