Phylum Porifera lab
Prepared slides – Scypha/Grantia (c.s)
-Grantia choanocytes
-Grantia spicules
-commercial sponge fibers - Leucoselenia
Preserved samples – Hydrozoa
-Anthozoa
-Scyphozoa
Various sponges
Demo slides – sponge gemmules
-leucoselenia longitudinal section
-Scypha (Grantia) longitudinal section
In this portion of the lab, you will exam some of the classes of Cnidarians we studied in lecture
Members of the Phylum Porifera are among the simplest of animals. They are little more than loose aggregations of cells
with little or no true tissue organization. There is some division of labor amongst the cells, but there are no organs.
The basic body form of all sponges is a sac-like structure consisting of three layers - an outer layer of epidermal cells
called a pinacoderm (made by pinacocytes); an inner layer of cells, many of which are flagellated cells called
choanocytes; and a middle layer made up of numerous cells types called a mesophyll. At the base of the choanocytes
are amoebocytes that have many functions such as feeding and sponge regeneration. These layers are perforated by a
large number of small pores made up of cells called porocytes (thus the name Porifera). The term ostia is used to mean
the openings into the pores. The cavity of the sponge is called the spongocoel and has at least one opening to the
outside, called an osculum.
The sponges are taxonomically classified based on the type of skeletal materials produced in the mesoglea: calcareous
spicules (the calcerous sponges or Class Calcerea), siliceous spicules (the glass-like sponges or Class Hyalospongia), or
proteinaceous spongin fibers (Class Desmospongia).
Within each class, the sponges can be further differentiated by body type. In asconoid sponges the body wall is not
folded. Asconoid sponges have the simplest organization. Choanocytes line the
spongocoel, drawing water through small ostia and expelling it through the
osculum. In syconoid sponges the body wall is folded. The "folds" form radial
canals and are lined with choanocytes rather than the spongocoel. The radial
canals open into the spongocoel via openings called apopyles.
In leuconoids sponges the canals formed by the folded body wall are extensively
branched and lined with even more choanocytes. Leuconoid sponges represent
the most complex body form. The canal system is extensively branched. Small
incurrent canals lead to flagellated chambers lined by choanocytes. Flagellated
chambers discharge water into excurrent canals that eventually lead to an
osculum. Usually there are many oscula in each sponge.
Synconoid sponge
In all sponge types, the body is designed to facilitate feeding. Water is pulled into the pores
and canals by the beating of the choanocytes' flagella. The water moves into the spongocoel
and is eventually forced out through the osculum. As the water passes across the
Leuconoid sponge
choanocytes, food particles (microscopic algae, bacteria, and organic debris) adhere to the cells and are eventually taken
into food vacuoles for intracellular digestion.
Class Calcerea – the calcerous sponges
Calcerous sponges will have large amounts of calcium-based spicules in their mesoglea made by cells called sclerocytes.
You will be looking at prepared slides of Grantia (also called Scypha) which has a synconoid body form and a demo slide
of Leucosolenia, an asconoid sponge.
Exercise 1- Scypha - a Syconoid Sponge
Examine a cross section of Scypha (Grantia) using a compound microscope at low power. Draw the cross section,
labeling the spongocoel; the radial canals that radiate from the spongocoel and the apopyles (the openings into the
radial canals). Identify and label the ostia and the incurrent canals in your drawing. Can you see any spicules?
Exercise 2 -Examine a demo longitudinal section of this sponge and compare it to what you see in the cross section.
Exercise 3 - Leucoselenia - an Asconoid Sponge
Very few asconoid sponges exist today. Leucosolenia is an example. Examine prepared slides of Leucoselenia sponge
fibers (commercial sponge fibers). Can you see spicules?
Exercise 4 – Examine a demo slide of Leucoselenia in longitudinal section. Identify the spongocoel and the osculum. Look
for the ostia in the body wall. Can you see how the body wall differs from the slide of Scypha? Does it look simpler or
more complex?
Exercise 5 - Examine a preserved specimens of calcerous sponges using a dissecting microscope.
Class Demospongiae – your typical sponge
The "bath sponge" is an example of a leuconoid sponge. The skeleton of this sponge is made of a soft protein, called
spongin, rather than calcium carbonate or silica.
Exercise 6 - Examine demonstration materials showing the leuconoid body form.