Download Phylum Porifera

Phylum Porifera
Ms. Adams’ Zoology
Introduction to Sponges
• Diversity of species: About 8000 species
• Phylum Porifera
– From Greek ‘poros’ meaning ‘passage’ or ‘pore’
– Sponges have tiny openings all over their body,
hints the name ‘pore-bearers’
• Most ancient and primitive of all animals
• Most sponges are marine, some live in
freshwater
Introduction to Sponges
• Sponges were once thought to be plants because
they are sessile, but they are multicellular
animals.
• Sponges are different from other animals:
– Do not have a mouth or digestive tract (gut)
– No true tissue layers (endoderm, ectoderm,
mesoderm) or organ systems
• Biologists think that sponges evolved from singlecelled ancestors separately from all other animals
• The evolutionary line that gave rise to sponges
was a dead end. It produced no other living
groups.
Form and Function in Sponges
• Sponges do not have
true systems, but the
following structures
fulfill the sponges needs
(next slide):
Form and Function in Sponges
• Four Cell Types:
– Epidermal cells: flat cells form outer covering
(respiration and excretion)
– Pore cells: water and other substances enter
through these cylindrical cells
– Collar cells: make up inner cell layer
• Have collar of microvilli
• Have a flagellum: They wave these to maintain a steady
current that draws water in through pores.
Form and Function in Sponges
– Amoebocytes: amoebalike cells that crawl
around the jellylike inner
layer (using
pseudopodia) and
deliver food and O2 to
other cells
• Amoebocytes absorb
nutrients and remove
wastes.
• Amoebocytes make
spicules and create a
sponge skeleton.
Form and Function in Sponges
• Amebocytes make thin, spiny spicules from either
chalklike calcium carbonate (CaCO3) or glasslike
silica (SiO2).
• These spicules form the delicate skeleton of the
sponge.
• Softer sponges (e.g. natural bath sponges) consist
of fibers of a protein called spongin (more
flexible than spicules)
– Some sponge skeletons are made up of both spongin
and spicules.
Form and Function of Sponges
• Sponges are filter feeders. They sift microscopic
food particles from the water that passes through
them. All the digestion in sponges is intracellular
(takes place inside cells).
• Food particles in water stick to collar cells. Food
can either be engulfed by the collar cells and
digested (endocytosis) or passed on to the
amoebocytes and digested. The amoebocytes
deliver digested food to other parts of the
sponge.
Form and Function of Sponges
• The water flowing through a sponge serves as
its respiratory, excretory, and circulatory
system.
• Osculum: Water exits out of this hole
Reproduction
• Sponges use the “broadcast method” of
reproduction
1. Sexual reproduction: Sponges are
hermaphrodites (have both male and female
reproductive parts).
•
•
Sperm is released from collar cells in sponge A. Sperm
then enters pores of sponge B. Fertilization occurs
inside of sponge B (amoebocyte carries sperm to egg).
Flagellated larvae develop and leave by the osculum.
They drift off and settle elsewhere.
Reproduction
2. Asexual reproduction
•
•
Budding: Small growth falls off of sponge and grows a
new sponge
Gemmules: Sphere-shaped collections of
amoebocytes surround the spicules. They leave
sponge, settle, and wait for improved conditions.
Three Sponge Body Forms
• Ascon: simplest and least
common sponge body
form. They are vaselike.
1.
2.
3.
Ostia (outer openings)
lead directly to a
chamber called the
spongeocoel.
Choanocytes line the
spongeocoel and draw
water into the
spongeocoel through
the ostia.
Water exits through the
osculum, a single large
opening at the top.
Three Sponge Body Forms
• Sycon: sponge walls appear
folded
1.
2.
3.
Water enters through
openings called dermal
pores. Dermal pores are
the openings of the body
wall, called incurrent canals.
Incurrent canals connect to
radial canals, which lead to
the spongeocoel.
Choanocytes line radial
canals (not spongeocoel)
and move water from the
ostia, through the incurrent
and radial canals, to the
spongocoel, and out the
osculum.
Three Sponge Body Forms
• Leucon: branched canal
system
1.
2.
Water enters through ostia
and moves through
branched incurrent canals,
which lead to choanocytelined chambers. Canals
leading away from the
chambers are called
excurrent canals.
Proliferation of chambers
and canals has resulted in
the absence of a
spongeocoel and multiple
exit points (oscula) for
water leaving the sponge.
Three Classes of Sponges
• Phylum Porifera
– Class Calcarea
– Class Demospongiae
– Class Hexactinellida
• Sclerospongiae is no
longer considered a
class.
Class Calcarea
• Have spicules made of
calcium carbonate and
are needle-shaped or
have three or four rays.
• Ascon, leucon, or sycon
body forms.
• Strictly marine.
Class Demospongiae (Most sponges)
• Brightly colored sponges
that include one
freshwater sponge and all
bath sponges.
• Have spicules made of
silicon dioxide (SiO2) or
spongin or a combination
of both.
• Most sponges belong to
this class. (90%)
• Nearly all are leucon body
form.
Class Hexactinellida (Glass sponges)
• Usually found in deep
water on soft substrates
in the tropical West Indies
at approximately 450 to
900 meters in depth.
• Spicules are six pointed
and have a lattice-like
structure. They are made
of silica.
• Cup, vase or urn shaped.
Sycon or Leucon body
form.