1. “Lower” Invertebrates I: Sponges & Radiata
Chapter 8
“Lower” Invertebrates I: Sponges & Radiata

3. Key Concepts
Sponges are asymmetric, sessile animals that filter food from the water circulating through their bodies.
Sponges provide habitats for other animals.
Cnidarians and ctenophores exhibit radial symmetry.
Cnidarians possess a highly specialized stinging cell used to capture prey and for protection.

4. What Are Animals? Animals: multicellular
eukaryotic cells without cell walls
cannot produce their own food
Invertebrates or vertebrates (most animals are invertebrates)

5. Sponges Phylum Porifera Basic characteristics: no tissues or organs
asymmetric
sessile
Anon. Wiki Commons

6. Sponge Structure and Function

7. Sponge Structure and Function
3 basic body forms: leuconoid from most efficient, most common

8. Sponge Structure and Function
Nutrition and digestion
suspension/filter feeders
collar cells (choanocytes) filter out tiny food particles
pinacocytes and archaeocytes (a.k.a. amoebocytes) ingest larger food particles by phagocytosis
Most food digested and distributed to other cells by archaeocytes

9. Sponge Structure and Function
Reproduction in sponges
asexual reproduction
budding
fragmentation
sexual reproduction
most hermaphrodites
eggs from archaeocytes and sperm from modified collar cells

10. Fertilization
Sperm cell engulfed by a choanocyte
Egg cell
Sperm cell (modified choanocyte)
Embryo
Asexual reproduction
Sexual reproduction
Planktonic amphiblastula larva
Bud
Figure 8-4 SPONGE REPRODUCTION. Sponges can reproduce asexually (by budding) or sexually.
New sponge
New sponge
Larva settles and attaches to bottom or other surface
Figure 8-4 p193

11. Ecological Roles of Sponges
Competition
corals and bryozoans
Predator-prey relationships
few species eat sponges
spicules
chemical deterrents

12. Ecological Roles of Sponges
Symbiotic relationships
mutualistic or commensalistic hosts
organisms live within the canals

13. Ecological Roles of Sponges
Sponges and nutrient cycling
boring sponges

14. Cnidarians: Animals with Stinging Cells
Include jellyfish, hydroids, corals and sea anemones
cnidocytes
ErgoSum88

15. Organization of the Cnidarian Body

16. Stinging Cells
Cnida
nematocysts

17. Stinging Cells
Dangerous species
Portuguese man-of-war
box jellyfish

18. Types of Cnidarians Hydrozoans or Hydroids mostly colonial
colonial forms contain 2 types of polyp:
Feeding polyp
Reproductive polyp
hydrocorals secrete a calcareous skeleton
some produce floating colonies (e.g. P. man-o-war)

19. Types of Cnidarians Jellyfish
scyphozoans—true jellyfish (class Scyphozoa)
plankton
medusa is predominant
photoreceptors

20. Types of Cnidarians Box jellyfish box jellyfish (class Cubozoa)
box-shaped bells
relatively strong swimmers
tropical
complex eyes (image-forming?)
voracious predators, primarily of fish

21. Types of Cnidarians Anthozoans (class Anthozoa)
include sea anemones, corals and gorgonians
sea anemones
benthic
gastrovascular cavity divided
though sessile, many can change locations

22. Types of Cnidarians Anthozoans (class Anthozoa) coral animals
polyps secrete a calcium carbonate skeleton
stony corals form reefs
Nick Hobgood

23. Types of Cnidarians Anthozoans (class Anthozoa) soft corals
polyps that form plant-like colonies

24. Nutrition and Digestion
Gastrovascular cavity
digestion and transport
1 opening: mouth/anus
Many suspension feeders
Jellyfish and box jellyfish are carnivorous
Sea anemones generally feed on invertebrates, some large species feed on fish, shallow water species have symbiotic algae

25. Reproduction asexual polyp stage sexual medusa stage
fission, budding common in corals
strobilation common in hydroids and jellyfish
sexual medusa stage

26. Reproduction Anthozoans asexual reproduction IS COMMON
pedal laceration
fission
budding
sexual reproduction
male and female forms, gametes are released
planula larva

27. Ecological Relationships of Cnidarians
Predator-prey relationships
cnidarians are predators
stinging cells discourage predation
sea turtles, some fish and molluscs prey on hydrozoans and jellyfish

28. Ecological Relationships of Cnidarians
Habitat formation
coral polyps form complex 3-dimensional structures inhabited by thousands of other organisms
coral reefs provide a solid surface for attachment, places for pelagic animals to rest and hide and buffer waves and storms
Terry Hughes

29. Ecological Relationships of Cnidarians
Symbiotic relationships
Portuguese man-of-war and man-of-war fish
reef-forming corals and zooxanthellae
sea anemones:
clownfish
hermit crab

30. Ctenophores Planktonic, nearly transparent Ctenophore structure
8 rows of comb plates
radial symmetry
lack stinging cells
bioluminescent

31. Ctenophores Digestion and nutrition Gastro-vascular cavity
feeds on plankton, larval fish and fish eggs
branched tentacles, adhesive cells, jellyfish stingers to capture prey