1. IB-202-2

2. Invertebrates Sponges
Chapter 33
Invertebrates
Sponges

3. Overview: Life Without a Backbone Invertebrates
Are animals that lack a backbone
Account for 95% of known animal species
Figure 33.1

4. A review of animal phylogeny
Ancestral colonial
choanoflagellate
Eumetazoa
Bilateria
Deuterostomia
Porifera
Cnidaria
Other bilaterians (including
Nematoda, Arthropoda,
Mollusca, and Annelida)
Echinodermata
Chordata
Figure 33.2

5. Sponges are sessile and have a porous body and choanocytes
Sponges, phylum Porifera
Live in both fresh and marine waters
Lack true tissues and organs

6. Sponges are suspension feeders
Capturing food particles suspended in the water that passes through their body
Azure vase sponge (Callyspongia
plicifera)
Osculum
Spicules
Water
flow
Flagellum
Collar
Food particles
in mucus
Choanocyte
Phagocytosis of
food particles
Amoebocyte
Choanocytes. The spongocoel
is lined with feeding cells called
choanocytes. By beating flagella,
the choanocytes create a current that
draws water in through the porocytes.
Spongocoel. Water
passing through porocytes
enters a cavity called the
spongocoel.
Porocytes. Water enters
the epidermis through
channels formed by
porocytes, doughnut-shaped
cells that span the body wall.
Epidermis. The outer
layer consists of tightly
packed epidermal cells.
Mesohyl. The wall of this
simple sponge consists of
two layers of cells separated
by a gelatinous matrix, the
mesohyl (“middle matter”).
The movement of the choanocyte
flagella also draws water through its
collar of fingerlike projections. Food
particles are trapped in the mucus
coating the projections, engulfed by
phagocytosis, and either digested or
transferred to amoebocytes.
Amoebocyte. Amoebocytes
transport nutrients to other cells of
the sponge body and also produce
materials for skeletal fibers (spicules). 5 6 7 4 3 2 1
Figure 33.4

7. Choanocytes, flagellated collar cells
Generate a water current through the sponge and ingest suspended food
Most sponges are hermaphrodites
Meaning that each individual functions as both male and female
Experiment: If a sponge is forced through
a fine mesh screen and the cells put in a
Beaker, within a few days they will reassemble
and form an intact sponge. What does this
mean? Do sponge cells communicate with each
other?

8. Variations in Form or Shapes of Sponges
Sponges come in a variety of shapes, sizes and
Colors!
Since sponges are an aggregation of cells and
not organized into tissues, how do they achieve this variability in structure and color??? Something to think about!

9. Episode 1- Origins (Sponges) The Story of Science.
Video
The Shape of Life
Episode 1- Origins (Sponges)
The Story of Science.

10. One hypothesis of animal phylogeny based mainly on molecular data
Calcarea
Silicarea
Ctenophora
Cnidaria
Echinodermata
Chordata
Brachiopoda
Phoronida
Ectoprocta
Platyhelminthes
Nemertea
Mollusca
Annelida
Rotifera
Nematoda
Arthropoda
“Radiata”
“Porifera”
Deuterostomia
Lophotrochozoa
Ecdysozoa
Bilateria
Eumetazoa
Metazoa
Ancestral colonial
flagellate
Figure 32.11

11. One hypothesis of animal phylogeny based mainly on morphological and developmental comparisons
Porifera
Cnidaria
Ctenophora
Phoronida
Ectoprocta
Brachiopoda
Echinodermata
Chordata
Platyhelminthes
Mollusca
Annelida
Arthropoda
Rotifera
Nemertea
Nematoda
“Radiata”
Deuterostomia
Protostomia
Bilateria
Eumetazoa
Metazoa
Ancestral colonial
flagellate
Figure 32.10

12. Phylum Cnidaria
Cnidarians have radial symmetry, a gastrovascular cavity, and cnidocytes
All animals except sponges
Belong to the clade Eumetazoa, the animals with true tissues
Phylum Cnidaria
Is one of the oldest groups in this clade

13. Cnidarians
Have diversified into a wide range of both sessile and floating forms including jellies, corals, and hydras
But still exhibit a relatively simple diploblastic, radial body plan

14. The basic body plan of a cnidarian
Is a sac with a central digestive compartment, the gastrovascular cavity
A single opening
Functions as both mouth and anus

15. There are two variations on this body plan
The sessile polyp and the floating medusa
Mouth/anus
Tentacle
Gastrovascular
cavity
Gastrodermis
Mesoglea
Epidermis
Body
stalk
Medusa
Polyp
Figure 33.5

16. Cnidarians are carnivores The tentacles are armed with cnidocytes
That use tentacles to capture prey
The tentacles are armed with cnidocytes
Unique cells that function in defense and the capture of prey
Tentacle
“Trigger”
Nematocyst
Coiled thread
Discharge
Of thread
Cnidocyte
Prey
Figure 33.6

17. The phylum Cnidaria is divided into four major classes
Table 33.1

18. Hydrozoa, Scyphozoa, Cubozoa, and Anthozoa
(a) These colonial polyps are members of class Hydrozoa.
(b) Many species of jellies (class Scyphozoa), including the species pictured here, are bioluminescent. The largest scyphozoans have tentacles more than 100 m long dangling from a bell-shaped body up to 2 m in diameter.
(c) The sea wasp (Chironex fleckeri) is a member of class Cubozoa. Its poison, which can subdue fish and other large prey, is more potent than cobra venom.
(d) Sea anemones and other members of class Anthozoa exist only as polyps.
Figure 33.7a–d

19. Hydrozoans Most hydrozoans Alternate between polyp and medusa forms
Other polyps, specialized
for reproduction, lack
tentacles and produce tiny
medusae by asexual budding. 3
Some of the colony’s
polyps, equipped with tentacles,
are specialized for feeding. 2
The medusae
swim off, grow, and
reproduce sexually. 4
Feeding
polyp
Reproductive
Medusa
bud
ASEXUAL
REPRODUCTION
(BUDDING)
Gonad
MEIOSIS
FERTILIZATION
SEXUAL
Egg
Sperm
Developing
Portion of
a colony
of polyps
Mature
Planula
(larva)
Key
Haploid (n)
Diploid (2n)
1 mm
Zygote
Figure 33.8
A colony of
interconnected
polyps (inset,
LM) results
from asexual
reproduction
by budding. 1
The planula eventually settles
and develops into a new polyp. 6
The zygote develops into a
solid ciliated larva called a planula. 5

20. Scyphozoans In the class Scyphozoa
Jellies (medusae) are the prevalent form of the life cycle

21. Cubozoans
In the class Cubozoa, which includes box jellies and sea wasps. Nematocysts full of
toxic venom
The medusa is box-shaped and has complex eyes unlike scyphozoa

22. Anthozoans Class Anthozoa includes the corals and sea anemones
Which occur only as polyps