1. Chapter 8 Marine Biology
Marine Invertebrates

2. What Are Animals? Animals: are multicellular
distinguishes them from bacteria and most protists
have eukaryotic cells without cell walls
distinguishes them from bacteria, fungi, algae and plants
cannot produce their own food, depend on other organisms for nutrients
can actively move at least at some point during their life cycle
invertebrates = animals that lack a vertebral column (backbone
vertebrates – animals with a vertebral column
majority of animals in sea are invertebrates

3. The first animals we will talk about are sponges
They are assymetrical – no symmetry
No true tisses

4. Phylum Porifera: Sponges
Basic characteristics:
simple
asymmetric
sessile: permanently attached to a solid surface
have many shapes, sizes and colors

5. Water exits through osculum Spicule Archaeocyte Pinacocyte Water
enters
through
small
pores
(ostia)
Spongocoel
(choanocyte)
Collar
cell
Spongocoel
Archaeocyte
Spicule
Pinacocyte
Pore cells
Ostium
Flagellum
Collar
Food particles
Stepped Art
Fig. 8-1, p. 193

6. Sponge Structure and Function
Lacking tissues, sponges have specialized cells
choanocytes use their flagella to provide force for moving water through the sponge’s body

7. 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 sponging
Helps also with protection – will keep other animals from eating the sponges

8. 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

9. 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

10. 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

11. Now we will talk about animals with radial symmetry

12. Phylum Cnidaria Animals with stinging cells
Include jellyfish, hydroids, corals and sea anemones
Named for their cnidocytes—stinging cells
Cnidocytes are used to capture prey and protect the animal

13. Organization of the Cnidarian Body
Radial symmetry: many planes can be drawn through the central axis that will divide the animal into equivalent halves
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)
Many cnidarians have both body plans, corals and sea anemones exist as polyps

14. Figure 8-5 (b) CNIDARIAN BODY PLANS..

15. Stinging Cells Cnidocytes have nematocysts
nematocysts: discharged when it contacts another object

16. Figure 8-6 (b) CNIDARIAN STINGING CELLS.

17. Stinging Cells Why do they need stinging cells? Dangerous species
They have very flimsy body plan. They must paralyze their prey (sometimes a large fish), so that they can digest it
Dangerous species
Portuguese man-of-war (painful stings)
box jellyfish (can kill within 3-20 minutes)

18. Groups of cnidarians
hydrozoans
Anthozoans
Scyphozoans
cubozoans

19. Hydrozoans (class Hydrozoa)
mostly colonial
hydrozoans known as hydrocorals secrete a calcareous skeleton, e.g., fire coral
some produce floating colonies
e.g. Portuguese man-of-war

20. Figure 8-8 (a) HYDROZOANS.

21. Figure 8-8 (b) HYDROZOANS.

22. Jellyfish and box 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

23. Anthozoans (class Anthozoa)
include sea anemones, corals and gorgonians
Sea anemones
benthic, all adults are sessile
polyps with a gastrovascular cavity divided into compartments radiating from the central one
though sessile, many can change locations

24. Figure 8-13 (a) ANTHOZOANS.

25. Anthozoans (class Anthozoa)
Coral animals
polyps that secrete a hard or soft skeleton
scleractinian corals = hard, stony corals
form reefs along with coralline red algae and calcified green algae

26. Anthozoans (class Anthozoa)
soft corals
polyps that form plant-like colonies

27. Nutrition and Digestion
Gastrovascular cavity: central cavity where cnidarians digest their prey
functions in digestion and transport
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

28. 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
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

29. Ecological Relationships of Cnidarians
Symbiotic relationships
Portuguese man-of-war and man-of-war fish
reef-forming corals and zooxanthellae
The zooxanthellae (dinoflagellate algal protist) provide food and oxygen to coral through photosynthesis
Coral provides nutrients and carbon dioxide to algae through respiration
sea anemones...
Have symbiotic relationship with the clownfish

30. Figure 8-17 (b) SYMBIOSIS.

31. Phylum Ctenophora Phylum Ctenophora Planktonic, nearly transparent
Ctenophore structure
named for 8 rows of comb plates (ctenes) which the animal uses for locomotion
ctenes are composed of large cilia
exhibit radial symmetry
lack stinging cells
bioluminescent

32. Figure 8-18 (a) CTENOPHORES.

33. Ctenophores Digestion and nutrition
carnivorous, feeding on other plankton, larval fish and fish eggs
may use branched tentacles in a net pattern, adhesive cells, jellyfish stingers to capture prey

34. Ctenophores Ecological Role
can effect zooplankton abundance directly and fish populations by preying on fish larvae and eggs

35. Now we will talk about animals with bilateral symmetry – all other animals have this type of symmetry
Bilateral symmetry
body parts arranged such that only one plane through the mid-line of the central axis 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)

36. Phylum Platyhelminthes
Flatworms
Have flattened, bilaterally symmetrical bodies with a definite head and posterior end
3 groups
Turbellaria – free living
Trematoda – parasitic flukes
Cestoda – parasitic tapeworms

37. Figure 8-19 (upper) BILATERAL SYMMETRY.

38. Figure 8-19 (lower) BILATERAL SYMMETRY.

39. Flatworms Types of flatworm
turbellarians are mostly pelagic, and are common members of meiofauna (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

40. Lophophorates
Lophophorates are sessile animals that lack a distinct head
Possess a lophophore: arrangement of ciliated tentacles that surround the mouth, used for feeding, gas exchange
3 phyla of lophophorates:
Phoronida (phoronids)
Ectoprocta (bryozoans)
Brachiopoda (brachiopods)

41. Phoronids Small, worm-like animals
Secrete a tube of leathery protein or chitin that can be attached or buried in bottom sediments
Catch plankton and detritus with mucus-coated tentacles
Can reproduce sexually or asexually (budding, transverse fission)
Have a planktonic larval stage

42. Bryozoans Small, abundant, colonial animals
Most live on rocks, shell, algae, mangroves, etc. in shallow water
Along with hydroids, rank among the most abundant marine epiphytic animals
Most are hermaphroditic brooders
Larvae are planktonic, settle to form new colonies

43. Figure 8-22 (b) REPRESENTATIVE LOPHOPHORATES.

44. Brachiopods
Most brachiopods (lamp shells) are benthic and live in shallow water
changed little since they evolved 400 million years ago
Have mollusc-like, bivalve shells
valves differ in size and shape, and are dorsal and ventral
a pedicle (fleshy stalk) attaches the shell or is buried
Gather detritus/algae with lophophore
Generally have separate sexes; larvae are planktonic and settle in hrs.

46. Ecological Roles of Lophophorates
As a group, they are filter feeders
Food for many invertebrates, especially molluscs and crustaceans
Largely responsible for fouling ship bottoms