1. Origins of Multicellular Animals

2. Three Hypotheses Syncytial ciliate hypothesis
Ancestor is single celled ciliate with multiple nuclei
Colonial flagellate hypothesis
Ancestor is colonial flagellate like Volvox
Polyphyletic hypothesis
There may be multiple ancestors

3. THE PHYLUM PORIFERA

5. INTRODUCTION TO PORIFERA
unusual animals
originally thought they were plants
Are primarily marine, mostly in shallower waters
Are sessile and attached to substrate or objects- occasionally on other animals such as crabs
Are the most primitive metazoans and have neither true tissues or organs

6. Morphology of Sponges

7. Sponge Cell Types
Pinacocytes- outer cells; equivalent of epiderm

8. Sponge Anatomy Porocyte Amoebocyte Pinacocyte Choanocyte
Cross section of a sponge wall.
A. H2O path from incurrent leading to the spongocel.
II. Note the different cell types that make up the cell wall as we take a closer look at the different cell types.
Choanocyte
Pechenik, 1996

9. Sponge Cell Types
Pinacocytes- outer cells covering sponge; equivalent of epidermis
Choanocytes-
similar to choanoflagellates
collared cells with flagella - create water current and collect food matter.

10. Sponge Anatomy Porocyte Amoebocyte Pinacocyte Choanocyte
Cross section of a sponge wall.
A. H2O path from incurrent leading to the spongocel.
II. Note the different cell types that make up the cell wall as we take a closer look at the different cell types.
Choanocyte
Pechenik, 1996

11. Sponge Cell Types
Pinacocytes- outer cells covering sponge; equivalent of epiderm
Choanocytes-
similar to choanoflagellates
collared cells with flagella - create water current and collect food matter
Amoebocytes-
amoeba-like cells
store, digest and transport food, excrete wastes, secrete skeleton
give rise to buds in asexual reproduction

12. Mesophyl (=Mesenchyma)
Beneath the pinacocytes - a gelatinous protein layer
it contains the skeletal material (ie. spongin and spicules) and amoebocytes

13. Sponge Anatomy Porocyte Amoebocyte Pinacocyte Choanocyte
Cross section of a sponge wall.
A. H2O path from incurrent leading to the spongocel.
II. Note the different cell types that make up the cell wall as we take a closer look at the different cell types.
Choanocyte
Pechenik, 1996

14. Types of Spicules 4 general types
Monaxon- needle-like or rod-like; straight or curved

16. Types of Spicules 4 general types
Monaxon- needle-like or rod-like; straight or curved
Tetraxon- has 4 prongs

18. Types of Spicules 4 general types
Monaxon- needle-like or rod-like; straight or curved
Tetraxon- has 4 prongs
Triaxon or Hexaxon- 3 or 6 rayed
Polyaxon- multiple short rods radiating from a common center; burr shaped, star shaped or like a child's jack.
Some species have a mixture of types

19. Spongin Give phylum its common name
Some species have no spicules, but do have spongin
spongin is a type of hardened secreted protein
Some species have both spicules and spongin

21. Three Basic Sponge Types
Asconoid
Syconoid
Leuconoid

23. Asconoid Sponges most primitive and simplistic in structure
have radial symmetry
are tube shaped

24. Asconoid Sponge two basic openings
Ostia-
incurrent pores that open into a central cavity called the spongocoel
it is lined with choanocytes or collar cells
Osculum
the opening of the spongocoel to the outside
water leaves the sponge

26. Asconoid Sponge Design
Imposes definite size limits to sponges due to the problem of water flow
The spongocoel contains such a large volume of water that it is hard to push it out rapidly

27. Syconoid Sponges next level of complexity
walls are invaginated
allowing for greater surface area over which water can pass
typically vase shaped like the asconoid sponges
radial symmetry

29. Syconoid Structure helps to rectify some of the water movement problem
increasing the surface area
so there are more choanocytes to water volume
decreasing the spongocoel volume
these sponges able to get bigger than asconoid

30. Leuconoid Sponges highest level of complexity in sponges
lost radial symmetry and are very irregular in shape and may attain large sizes
invaginated canals are even further invaginated and folded to from small flagellated chambers

31. Leuconoid Sponge Design
further increase in surface area makes these sponges highly efficient in moving and filtering water
spongocoel is gone except for canals that lead to the osculum- or there may be a series of excurrent openings
the largest sponges; most hydrologically efficient

33. Sponge Reproduction
Sexual
Asexual

34. Sexual Reproduction in Sponges
gametes formed by amoebocytes
there are both hermaphroditic and dioecious species
most hermaphroditic species produce eggs and sperm at different times so they do not self fertilize
sperm is released into environment via osculum and is brought in by another sponge via ostia
fertilization takes place in parent sponge
zygote is expelled - it drops to bottom and begins to develop

35. Asexual Reproduction in Sponges
two types:
Budding- fragmentation of body wall, buds appear as outgrowth on sides of sponge
when they reach a certain size they drop off and settle to bottom to form a new sponge
Gemmules- occurs only in freshwater sponges
gemmules are groups of food laden amoebocytes that deposit a hard covering of spicules around them
formation is triggered by environmental conditions such as decreased temperatures
they allow the sponge to pass the winter or periods of drought
after which the outer covering breaks open and a new sponge develops

37. Osmoregulation and Excretion in Sponges
no special organs
main waste is ammonia
it is removed by water currents within the sponge

38. HIGHER CLASSIFICATION OF SPONGES
4 classes of sponges

39. Class Calcarea spicules composed of calcium carbonate
spicules are monaxons or tri or quadraxons
all three types of sponges exhibited
All less than 10 cm high
ex. Leucosolenia and Grantia
found in shallow coastal waters
all are marine

40. Class Hexactinellida (glass sponges)
Spicules of Silica and fused to form a lattice like skeleton
cup or vase shaped with well developed spongocoel
most beautiful example is Euplectella - venus flower basket
chiefly live in meter depth
are syconoid sponges
all are marine
may have commensal relationship with shrimp - where a male and female live inside the sponge; get trapped inside when they out-grow the pores of sponge

41. Class Demospongiae Largest class - 95% of sponges in this class
spicules are silicious if present otherwise skeleton is made of spongin
variously shaped some are huge
all are leuconoid
all but one family is marine- Spongillidae- is freshwater about 150 freshwater species
this is the group from which we get our commercial sponges

42. Class Sclerospongiae
proposed in 1970 to include 6 species from Jamaica
have silicious spicules and spongin
also have an outer covering composed of calcium carbonate
are leuconoid sponges