Phylum Porifera: Sponges
Chapter 6
The Sponges
• Phylum Porifera (Latin porous, “pore”;
ferre : “to bear”).
• About 5,500 living species most marine
although there are about 200 freshwater
species.
Characteristics of Sponges
• Metazoa: without true tissue. Cellular grade of complexity
(Parazoa).
• Adults asymmetrical or superficially radially symmetrical.
• Unique flagellated cells the choanocytes that drive water
through canals and chambers: the aquiferous system.
• Adults sessile suspension feeders; larval stages are motile.
• Reproduction sexual or asexual.
The Poriferan Bauplan
• Two unique organizational attributes:
– The aquiferous system
– Highly totipotent nature of sponge cells
Overview of general structures
• Sponges move water through their bodies
using choanocytes
• All cells are loosely arranged into a
gelatinous matrix, the mesohyle
• Water enters small holes called ostia
• Water exits large holes called oscula
• A skeleton helps maintain the structure of
the sponge.
Body Structure and the Aquiferous System
The mesohyl includes a non cellular coloidal
mesoglea in which are embedded collagen fibers,
spicules and various cells.
Dermal pores
or ostia
Most of these cells are able to change from one
type to another as required.
3)
Water flows through the ostia all the chanels and
eventually out through the osculum.
Types of Canal Systems
• Most sponges can be separated based on
their type of canal system.
1. Asconoid
2. Syconoid
3. Leuconoid
Asconoid sponges
• Found in radially symmetrical calcarous
sponges: rarely exceed 10cm in height.
Asconoid sponges
• Simple organization
• Water moves
through the ostia
into the spongocoel
• Choanoderm simple
and continuous one
cell thick.
Fig. 6.3
Asconoid condition
Choanoderm simple and
continuous one cell thick.
Fig. 6.3
Asconoid water flow
3
Water flow: 1) ostium 
2) choanoderm  3) osculum
2
1
#1
#2
#3
Syconoid sponges
• Syconoid condition: simple folding of the
pinacoderm and choanoderm.
• As complexity increases the mesohyl may
thicken and appear to have two layers.
• Water is brought in through the incurrent
canals and then to radial canals (lined with
choanocytes).
Fig. 6.3
Syconoid condition
Choanoderm restricted to
chambers with an apopyle
opening into the atrium.
Fig. 6.3
Syconoid water flow
Water flow: 1) incurent pore
 2) incurrent canal 
3) prosopyle  4) choanocyte
chamber  5) apopyle 
6) atrium  6) osculum
Leuconoid sponges
• Additional folding of the choanoder and
further thickening of the mesohyl.
• Water is brought in through incurrent
canals, and discharged through excurrent
canals.
• Most common type.
Fig. 6.3
Leuconoid condition
The atrium is reduced to a
series of excurrent canals.
Water flow: 1) dermal pore
 2) incurrent canal 
3) prosopyle  4) choanocyte
chamber  5) apopyle 
6) excurent canal 
7) osculum
• The more complex a sponge condition the
more particles it can filter from the water
column.
Types of Cells
I.
II.
III.
IV.
Pinacocytes (Epidermal Cell)
Porocytes (Water Flow Through Cell)
Choanocytes (Collar Cells)
Archeocytes (Amoebocytes)
I. Pinacocytes
• Cells of the external epithelium
• Main functions:
– Structure
– Contraction
II. Porocytes
• Cells which form
pores
• Function: to allow
water flow
III. Chanocytes
• Line the flagellated canals and chambers.
• Main function: to create water flow.
Codosiga
Sponge feeding
Diameter of
channels influences
water flow velocity.
Particles that are
captured are in the
2-5 µm range.
Predatory sponges
Cladorhizid
carnivorous sponge
The Harp Sponge, Chondrocladia lyra
IV. Archaeocytes
• Amoeboid cells which can be non-sessile
• Found in cellular matrix
• Main function:
– Digestion
– Secrete structural components
• Spongin
• Spicules
Sponge feeding
Sclerocyte in the process of secreting a
spicule
Keeping the mesohyle together
• Spongin
• Spines (spicules)
– Siliceous
– Calcareous
Spongin
• Fibers of collagen
Spicules
• Spines, when placed together form a very
rigid skeleton
Megascleres And Microscleres
m
M
Main Groups of Sponges
• P: Porifera
– C: Calcarea
– C: Hexactinellida
– C: Desmospongiae
Calcarea
• Calcareous sponges
• Spicules composed
of calcium
carbonate
• Small < 10 cm tall
Calcareous sponges
Hexactinellida
• Glass sponges
• Some spicules fused to form skeleton
• Spicules made of glass (Siliceous spicules)
six rayed
• Deep water sponges
Siliceous spicules in
Hexactinellida
(Triaxon) six rayed
spicules.
Desmospongiae
• Common sponges
• Skeleton is variable
– Spicules
– Spongin
– both
• Can be large
Siliceous Spiculse in Desmospongia
Never six-rayed
Microscleres
Megascleres
Sclerospongiae
Sclerosponges were first proposed as a class of sponges, in 1970
by Hartman and Goreau.
Sclerosponges are sponges with a soft body that covers a hard,
often massive limestone basal skeleton.
Because of their long life span (500-1,000 years) it is thought
that analysis of these sponges could extend data regarding
ocean temperatures, salinity, and other variables farther into
the past than has been previously possible.
However, it was later found that the sclerosponges are not a
monophyletic group (they are polyphyletic) and therefore this
class is currently not recognized.
The Big Picture
• Sponges are metazoans, but don’t have
true tissues
• They are an ancient group
• Three main groups (taxonomic), which
fall into three main structural groups
• Four types of specialized cells
*choanocyte*