1. Chapter 8
Lower Invertebrates

2. What Are Animals? Animals: are multicellular
have eukaryotic cells without cell walls
cannot produce their own food, depend on other organisms for nutrients
can actively move
invertebrates = animals that lack a vertebral column (backbone)
vertebrates – animals with a vertebral column
majority of animals in sea are invertebrates

3. Body Structure Dorsal – Top Ventral – Bottom/belly Anterior – Head
Posterior - Tail

4. Body Symmetry Asymmetry – No symmetry
Radial – Arrangement of body parts around a central axis
- Top & bottom, No front, back, or right & left sides
– Allows for organism to take in stimuli from all sides

5. Bilateral symmetry – 2 similar halves on either side of a central plane
Adaptation for movement

6. Cephalization
Concentration of sensory & brain structures in the Anterior region
No-cephalization

7. Sponges Phylum Porifera Basic characteristics: Simple Asymmetric
Sessile: Permanently attached to a solid surface
Have many shapes, sizes and colors
Shape often determined by shape of bottom sediments, material on which they are growing and local water currents

8. Sponges have specialized Cells but NO Tissues
Most primitive animals on Earth

9. Sponge Structure and Function
Body is built around a system of water canals
Ostia: Tiny holes or pores through which water enters the sponge’s body
Spongocoel: Spacious cavity in the sponge into which water flows
Osculum: Large opening through which water exits from the spongocoel

10. Sponge Structure and Function
Lacking tissues, sponges have specialized cells
Collar cells (Choanocytes) use their flagella to provide force for moving water through the sponge’s body
Amoebocytes: Cells that resemble amoebas, and can move through sponge body
Transport materials

11. Sponge Structure and Function
Structural materials
Spicules: Skeletal elements that give support to a sponge’s body, produced by specialized cells and composed of calcium carbonate, silica or spongin
Spongin: A protein that forms flexible fibers

12. Sponge Structure and Function
Sponge size and body form
Size is limited by water circulation
Asconoid: Simplest form; tubular and always small, found in clusters
Syconoid: Sponges that exhibit the first stages of body-wall folding
Leuconoid: Sponges with the highest degree of folding, which have many chambers lined with collar cells

13. Osculum
Ostia
Choanocyte
Spicules
Amoebocyte

14. Sponge Structure and Function
Nutrition and digestion
Sponges are suspension feeders – feed on material suspended in seawater
Sponges are also referred to as Filter Feeders – they filter food from the water
Large particles are engulfed and digested by pinocytes and archaeocytes
Collar cells trap ~ 80% of food which consists of small particles (0.1 to 1.0 micrometers in size)
Sponges are one of the few animals that can capture such small sized particles

15. Sponge Structure and Function
Reproduction in sponges
Asexual reproduction
Budding: Group of cells on the outer surface of the sponge develops and grows into a tiny new sponge, which drops off and establishes itself
Fragmentation: Production of a new sponge from pieces that are broken off by physical processes, e.g., waves, storms, predators
Sexual reproduction
Most sponges are Hermaphrodites
Larval stage is called a planktonic Amphiblastula

16. Ecological Roles of Sponges
Competition
Compete aggressively with corals and bryozoans for attachment space
Predator-prey relationships
Few species eat sponges
Spicules are like needles
Some produce chemical deterrents
A few species of bony fish and molluscs and sea turtles (especially the hawksbill) will eat sponges

17. Ecological Roles of Sponges
Symbiotic relationships
Sponges are Mutualistic or Commensalistic hosts to many organisms
e.g. symbiotic cyanobacteria
Many organisms (shrimp, fish) live within the canals or spongocoel, for protection and to take advantage of water flow

18. Ecological Roles of Sponges
Sponges and nutrient cycling
Boring sponges (family Clionidae) recycle calcium as they burrow into coral and mollusc shells

19. Sponge Dye in the Ocean

20. Phylum: Cnidaria Jellyfish, Anemone, Corals
Kingdom: Animalia
Phylum: Cnidaria
Jellyfish, Anemone, Corals

21. Cnidarians: Animals with Stinging Cells
Phylum Cnidaria
Include jellyfish, hydroids, corals and sea anemones
Named for their Cnidocytes—Stinging cells
Cnidocytes are used to capture prey and protect the animal

22. Organization of the Cnidarian Body
Often exhibit 2 body plans within their life cycles:
Polyp: Benthic form characterized by a cylindrical body with an opening at 1 end, i.e., the mouth which is surrounded by tentacles
Medusa: A free-floating stage (jellyfish)

23. Stinging Cells
Cnida: Stinging organelle within a cnidocyte, which may function in locomotion, prey capture, or defense
Nematocysts: Spearing type cnida, which are discharged when the cnidocill—a bristle-like trigger—contacts another object

24. Stinging Cells
Stinging cells also triggered by certain chemical substances released by prey
Dangerous species
Box jellyfish (can kill within 3-20 minutes)

25. Kingdom: Animalia Phylum: Cnidaria
Class: Hydrozoa
“water animals”

26. Types of Cnidarians Hydrozoans (class Hydrozoa) Mostly colonial
Colonial forms contain 2 types of polyp:
Gastrozooid = Feeding polyp
Gonangium = Reproductive polyp
Hydrozoans known as hydrocorals secrete a calcareous skeleton, e.g., fire coral
Some produce floating colonies
e.g. Portuguese man-of-war

27. Portuguese Man of War

28. Ex: Physalia Portuguese man-of-war
Colony of medusae and polyps
Gas-filled float:
Tentacles measure up to 65ft
Preys mostly on small fish-poison can be painful and even fatal to humans

29. Class: Scyphozoa “cup animals” True Jellyfish
Phylum: Cnidaria
Class: Scyphozoa
“cup animals”
True Jellyfish

30. Phylum: Cnidaria Class: Scyphozoa
Cup animals
Jellyfish
Medusa is the dominant form of the life cycle
Pulsating motions of the cup propel the jellyfish through the water
Some nematocysts cause severe pain and even death to humans

31. Types of Cnidarians Jellyfish
Scyphozoans—True jellyfish (class Scyphozoa)
Considered members of the plankton
Medusa is predominant life stage
Photoreceptors: Sense organs that can determine whether it is dark or light
Box jellyfish (class Cubozoa)
Box-shaped bells
Relatively strong swimmers
Tropical
Voracious predators, primarily of fish

32. Class: Anthozoa “flower animals” Sea Anemone & Coral
Phylum: Cnidaria
Class: Anthozoa
“flower animals”
Sea Anemone & Coral

33. Types of Cnidarians Anthozoans (class Anthozoa)
Include sea anemones, corals and gorgonians
Sea anemones
Benthic, all adults are sessile
Though sessile, many can change locations

34. Phylum: Cnidaria Class: Anthozoa
“Flower Animals”
Polyp form dominant
Sea Anemone
1. Attach themselves to rocks and other submerged objects
2. Feed on fishes and other animals

35. Corals
1. Small polyps live in colonies
2. calcium carbonate skeleton
degrees N or S of the equator
4. Shallow depths in warm, clear water
5. Zooxanthellae

36. Types of Cnidarians Anthozoans (class Anthozoa) Coral animals
Polyps that secrete a hard or soft skeleton
Hard, stony corals
Form reefs along with coralline red algae and calcified green algae

37. Types of Cnidarians Anthozoans (class Anthozoa) Soft corals
Polyps that form plant-like colonies

38. Nutrition and Digestion
Gastrovascular cavity: Central cavity where cnidarians digest their prey
Waste products forced back out mouth
Many hydrozoans and anthozoans are suspension feeders
Jellyfish and box jellyfish are carnivorous, eat fish and larger invertebrates
Sea anemones generally feed on invertebrates, some large species feed on fish, shallow water species have symbiotic algae

39. Reproduction Scyphozoans
in adult jellyfish and box jellyfish, sexes generally separate
medusae (sexual stage) release gametes into the water column for fertilization
planula larvae settle, grow into polyps, and reproduce medusa-like buds asexually
immature buds are released into the water column to grow into mature medusae

40. Ecological Relationships of Cnidarians
Predator-prey relationships
Cnidarians are predators
Sea turtles, some fish and molluscs prey on hydrozoans and jellyfish

41. Ecological Relationships of Cnidarians
Symbiotic relationships
Portuguese man-of-war and man-of-war fish
Reef-forming corals and zooxanthellae
Algae provide food and oxygen to coral through photosynthesis
Coral provides nutrients and carbon dioxide to algae through respiration
Sea anemones...
and Clownfish
and the Hermit crab

42. Phylum: Ctenophora
Comb jellies

43. Ctenophores Phylum Ctenophora Planktonic, nearly transparent
Ctenophore structure
Named for 8 rows of comb plates which the animal uses for locomotion
Are composed of large cilia
Exhibit radial symmetry
Lack stinging cells – Adhesive cells (sticky)
Bioluminescent

44. Phylum: Ctenophora Comb jelly - eight comb like rows of cilia
Move through water by beating their cilia
Colloblasts-secrete a sticky substance that binds to their prey
Apical organ-senses orientation in the water
Most hermaphroditic
Bioluminescence-production of light
Occur in large swarms near the surface of the ocean

45. Neon Killers

46. The Evolution Of Bilateral Symmetry
Body parts arranged such that only one plane through the mid-line divides animal into similar right and left halves
Allowed for streamline body shape increasing mobility
Favored concentration of sense organs at one end of animal (Cephalization)

47. Flatworms
Have flattened, bilaterally symmetrical bodies with a definite head and posterior end

48. Flatworms Types of Flatworm
Turbellarians are mostly pelagic, and are invertebrates living between sediment particles
Turbellarians have sensory receptors in head region to detect light, chemicals, movement and help maintain balance
Flukes usually have complex life cycles
Tapeworms live in the host’s digestive tract

49. Flatworms Ecological role of flatworms Turbellarians:
Turbellarians funnel nutrients to higher trophic levels
Prey for higher-level consumers
Parasitic flatworms:
Can regulate population size by lowering fitness of host

50. Ribbon Worms Phylum Nemertea Most are benthic
Resemble flatworms but are longer with thicker bodies
Sexes are separate, fertilization external
Carnivorous – Feed on annelids and crustaceans
Capture prey with proboscis (tube extending from mouth)

51. Ribbon Worms Ecological role of ribbon worms
Prey organisms for higher consumers
Burrowing in sediment moves nutrients to surface
Abandoned burrows can serve as habitat