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1. Phylum: Porifera
The Sponges

2. I. General Ecological Characteristics
Sponges are:
• Sessile, benthic
• Filter feeders
• Competitors for space
• Fed upon by specialist predators
• Grow in many forms, solitary,
colonial, branching, as thin
sheets over substrates
• From few cm to over 1 m in size
• Estimated in some cases to be
several hundred years old

3. The classification of sponges is based on skeletal morphology
II. General Characteristics of
the Porifera Body Plan

5. Water Flow
Through the
Sponge
WATER
IN
WATER
OUT
Osculu
m

6. D. Class Calcarea (Calcispongiae)
1. These are calcareous sponges with
spicules of calcium carbonate.
2. The spicules are straight or have three or
four rays.
E. Class Hexactinellida (Hyalospongiae)
1. These are glass sponges with six-rayed
spicules of silica.
2. Nearly all are deep-sea forms; most are
radially symmetrical.
F. Class Demospongiae
1. This class contains 95% of living sponge
species.
2. Spicules are siliceous but not six rayed;
they may be absent or bound together by
spongin.
3. All are leuconoid and all are marine except
for Spongillidae, the freshwater sponges.

7. 12.1. Advent of Multicellularity
A. Advantages
1. Nature’s experiments with larger
organisms without cellular
differentiation are limited.
2. Increasing the size of a cell
causes problems of exchange;
multicellularity avoids surface-to-
mass problems.
3. Cell assemblages in sponges
are distinct from other animals;
but molecular evidence shows
common ancestry.

8. 12.5. Phylum Porifera
A. General Features
1. Porifera means "pore-bearing"; their sac-like bodies
are perforated by many pores.
2. They are sessile and depend on water currents to
bring in food and oxygen and carry away wastes.
3. Their body is a mass of cells embedded in
gelatinous matrix and stiffened by spicules of
calcium carbonate or silica and collagen.
4. They have no organs or tissues; cells are
somewhat independent.
5. Being sessile, they have no nervous or sense
organs and have simplest of contractile
elements.
6. They are not from the mainstream of animal
evolution; thus they are often called Parazoa.
7. Most of the 5000 species are marine; about 150
are freshwater.
8. Morphology changes with substrate, calmness of
water, etc.
9. Sponges are ancient; fossils extend to Cambrian or
earlier.

9. B. Form and Function
1. Body openings consist
of small incurrent pores or
ostia and a few excurrent
oscula.
2. Openings are connected
by a system of canals;
water passes from ostia to
osculum.
3. Choanocytes or
flagellated collar cells line
some of the canals.
a. They keep the current
flowing by beating of
flagella.
b. They trap and
phagocytize food
particles passing by.
4. The framework of the
sponge is composed of
needle-like calcareous or
siliceous spicules or
organic spongin fibers.

10. Overview
 Diversity: three
major groups
 1. Calcarea:
Calcareous sponges
 Calcium carbonate
(calcite) spicules
 Primarily shallow
water and tropical
(some exceptions)
 2. Hexactinellida:
Glass Sponges
 Siliceous, 6-rayed
spicules
 Marine, primarily
deep water
Taxonomic Detail
Desmospongia
All other
classes

11. Overview
 Diversity: three
major groups
 3. Demospongiae:
Demosponges
 Siliceous spicules
(never 6-rayed)
and/or spongin for
support

12. 5. There are three
types of canal
systems.
a. Asconoids:
Flagellated
Spongocoels
1) Asconoids are
simplest; they are
small and tube-
shaped.
2) Water enters a
large cavity, the
spongocoel, lined
with choanocytes.
3) Choanocyte
flagella pull water
through.
4) All Calcarea are
asconoids:
Leucosolenia and
Clathrina are
examples.

13. b. Syconoids: Flagellated Canals
1) They resemble asconoids but are
bigger with a thicker body wall.
2) The wall contains choanocyte-
lined radial canals that empty into the
spongocoel. (Fig.12-7)
3) Water entering filters through tiny
openings.
4) Food is digested by choanocytes.
5) Flagella force the water through
internal pores into the spongocoel
and out the osculum.
6) The flagellated canals form by
evagination of the body wall; this is
developmental evidence of being
derived from asconoid ancestors.
7) Classes Calcarea and
Hexactinellida have species that are
syconoid.

14. c. Leuconoids: Flagellated
Chambers
1) These are most
complex and are larger
with many oscula. (Fig.
12-8)
2) Clusters of flagellated
chambers are filled from
incurrent canals,
discharge to excurrent
canals.
3) Most sponges are
leuconoid; it is seen in
most Calcarea and in all
other classes.
4) This system increases
flagellated surfaces
compared to volume;
more collar cells can
meet food demands. Its
all about surface-to-
volume ratios and
energy extraction!!!

15. 6. Types of Cells
a. Sponge cells are
arranged in a
gelatinous matrix
called mesohyl.
b. Pinacocytes
1) These cells form the
pinacoderm; they are
flat epithelial-like cells.
2) Pinacocytes are
somewhat contractile.

16. c. Choanocytes
1) These are oval cells
with one end embedded
in mesohyl.
2) The exposed end
has a flagellum
surrounded by a collar.
3) A collar is made of a
row of microvilli forming
a fine filtering device to
strain food. (Fig. 12-10)
4) Particles too large
to enter the collar are
trapped in mucous
and moved to the
choanocyte where
they are
phagocytized.
5) Food engulfed by
choanocytes is
passed to
neighboring
archaeocytes for
digestion.

17. 3) A collar is made of a row
of microvilli forming a fine
filtering device to strain food.
(Fig. 12-10)
4) Particles too large to
enter the collar are trapped
in mucous and moved to
the choanocyte where they
are phagocytized.
5) Food engulfed by
choanocytes is passed to
neighboring archaeocytes
for digestion.

18. d. Amoebocytes
(Archaeocyte)
1) These cells move
about in the mesohyl.
2) They phagocytize
particles in the
pinacoderm.
3) They can differentiate
into any other type of
cell.
4) Those called
sclerocytes secrete
spicules.
5) Spongocytes secrete
spongin.
6) Collencytes secrete
fibrillar collagen.
7) Lophocytes secrete
lots of collagen but may
look like collencytes.

19. e. Types of Skeletons
1) Collagen fibrils are
found throughout
intercellular matrix of
sponges.
2) Various
Demospongiae secrete
a form of collagen
called spongin.
3) Demospongiae also
secrete some siliceous
spicules.
4) Calcareous sponges
secrete spicules of
crystalline calcium
carbonate.
5) Glass sponges have
siliceous spicules with
six rays.
6) Spicule patterns are
important classification
features.

20. Spicule formation:
The sponge is a sessile (permanently attached; non-motile) animal. It
utilizes a proteoglycan-like molecule termed the aggregation factor
31-32 for its adhesive properties.4
Structural support is based upon the formulation of a endoskeleton.
Made up of collagen, spongin, and mineral sclera(spicules),the
skeleton stabilizes and protects the sponge. 5
Skeletal formation is based on mineral secretions of
calcite, aragonite, and/or silica. This formation also
functions by:
Precise control of intracellular calcium carbonate
precipitation releases protons, which contribute to the
acid pH maintenance necessary for sponge biological
processes.
HCO3+ Ca2 →CaCO3+H+ 4

21. 7. Sponge Physiology
a. Filtration Rates
1) Leuconia, a small sponge,
has 81,000 incurrent canals.
2) It would have more than
two million flagellated
chambers.
3.)Expulsion is strong enough
to disperse wastes.
4) Some large sponges can
filter 1500 liters of water a
day.
b. Particles are filtered
nonselectively; choanocytes
phagocytize 80%.
c. Digestion is completely
intracellular, primarily by
amoebocytes.
d. There are no excretory or
respiratory organs; diffusion
suffices.
e. The only movements are very
slow opening and closing of
pores; nerve cells are not
present.

22. C. Reproduction
1. Asexual Reproduction
a. External buds are small individuals that break off
after attaining a certain size.
b. Internal buds or gemmules are formed by
amoebocytes that collect in mesohyl and are coated
with tough spongin and spicules; they survive drought,
freezing, etc, and contain amoebocytes.
2. Sexual Reproduction
a. Most are monoecious with both male and female
sex cells in one individual.
b. Sperm arise from transformed choanocytes.
c. In some Demospongiae and Calcarea, oocytes
develop from choanocytes; others derive them from
archaeocytes.
d. Sponges provide nourishment to the zygote until it
is released as a ciliated larva.
e. In some species, sperm are released out into the
water where they enter the pores of other sponges.
f. Choanocytes phagocytize the sperm and transfer
them to carrier cells that carry sperm through mesohyl
to oocytes.
g. Some release both sperm and oocytes into water.

23. Branching Tube
Sponge

24. Stove Pipe
Sponge

25. Vase
Sponges

26. Barrel
Sponges

27. Ball Sponges

28. Rope
Sponges