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Chapter 8

Sponges, Cnidarians, Comb Jellies, and Marine Worms

Objectives

• Describe the structure and function of sponge biology.

• Understand the role sponges play in ecoystems.

• Differentiate between Cnidarians and ctenophores

• Describe how cnidarians capture food items and protect themselves from predators.

Objectives

• Describe the structure of marine worms.

• Define and give examples of meiofauna.

• Describe the body structure of polychaetes and explain how their form relates to their function.

I. What Are Animals?

• Animal characteristics:1. multicellular

– distinguishes them from bacteria and most protists

2. eukaryotic cells without cell walls– distinguishes them from bacteria, fungi,

algae and plants

3. heterotrophs4. motile - (with the exception of adult

sponges)

Marine Phyla

1. Porifera - sponges2. Cnidaria – corals, anemones, jellies 3. Ctenophores – comb jellies4. Platyhelminthes – flatworms, turbellaria5. Nematoda – round worms6. Mollusca – snails, clams, squid, octopus7. Annelida – sea worm, tube worm8. Arthropoda – lobster, crab and krill9. Echinodermata – sea stars, sea urchins, sea

cucumber10. Chordates – tunicates, salps, fish, reptiles,

birds, & marine mammals

II. Sponges

• Phylum Porifera• Basic characteristics:

– simple–asymmetric– sessile—permanently attached to a solid

surface–have many shapes, sizes and colors–approximately 5,000 species of sponges

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II. Sponges

• Phylum Porifera• Basic characteristics:

• three distinct groups: • Hexactinellida (glass sponges)• Demospongia• Calcarea (calcareous sponges).

Hexactinellida

Demospongia

( © Jeffrey L. Rotman/Corbis

. Reproduced by permission.)

Calcarea

http://bioweb.uwlax.edu/zoolab/Table_of_Contents/Lab-3a/Calcarea/Lab_3a-01a.jpg

www8.nos.noaa.gov

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–osculum—large opening through which

water exits from the spongocoel

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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

–pinacocytes provide an outer covering for the sponge

–archaeocytes—cells that resemble amoebas, and can move through the body• can assume any of the other cell forms, or

transport materials

Sponge Structure and Function

• Structural materials– spicules—skeletal elements that give

support to a sponge’s body, which are produced by specialized cells and composed of calcium carbonate, silica or spongin• spongin—a protein that forms flexible fibers

Sponge Structure and Function

• Sponge size and body form–Size

• limited by water circulation

–Body Form• asconoid—simplest form; tubular and always

small• syconoid—some folding of body-wall• leuconoid—many-chambered sponges with the

highest degree of folding

Sponge Structure and Function

• Nutrition and digestion– filter feeders – sponges are one of the few animals that

can capture particles 0.1 to 1.0 micrometers in size

Sponge Structure and Function

• Reproduction in sponges–asexual reproduction

• budding—a group of cells on the outer surface of the sponge develops and grows into a tiny new sponge, which drops off

• fragmentation—production of a new sponge from pieces that are broken off

– sexual reproduction• eggs usually develop from archaeocytes and

sperm from modified collar cells• larval stage is a planktonic

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Ecological Roles of Sponges• Competition

–compete for space to attach with corals and bryozoans

• Predator-prey relationships– few species eat sponges

• spicules are like needles• some produce chemical deterrents

*major food source for hawksbill sea turtles

Ecological Roles of Sponges

• Symbiotic relationships–sponges are mutualistic or commensalistic

hosts to many organisms• e.g. mutualistic bacteria

–many organisms live within the canals or spongocoel, for protection, water flow

Ecological Roles of Sponges

• Sponges and nutrient cycling–boring sponges recycle calcium as they

burrow into coral and mollusc shells

http://www.seaotter.com/marine/research/cliona/celata/pics/celata.jpg

Sponges of New EnglandFinger Sponge (Haliclona oculata) –Short stalk with flat to rounded finger-shaped branches. Light brown, gray-brown, or purple in color. Found attached to rock habitat from low tide line to 400'. Grows to 18" high.

Red Beard Sponge (Microciona prolifera)- Short branching sponge with flattened branches. Differs from Finger Sponge in color – orange to red. Found on rock, pilings and other solid substrate. Grows up to 8" high. Subtidal depths.Bread Sponge (Halichondria parma) -

Encrusting sponge found on rock, pilings, etc. Colors vary from brown, orange, yellow and green. Occurs in many shapes, but normally has cone-shaped bulges. Can grow to several feet in diameter. Can be difficult to identify. Intertidal to 200'.

Common Palmate Sponge (Isodictyapalmata) - Sponge with more flattened than rounded branches. Holes (oscula) in sponge are very obvious - more so than any other branching sponge in the region. Grows to 12" high. Color yellow, brown to orange. Found sub-tidally.

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II. Cnidarians: Animals with Stinging Cells

• Phylum Cnidaria• Named for their cnidocytes—stinging

cells• Cnidocytes are used to capture prey

and protect the animal

A. Organization

• 1. Radial symmetry• 2. Often exhibit 2 body plans within

their life cycles:–a. polyp—a benthic form characterized by

a cylindrical body with an opening at 1 end

–b. medusa—a free-floating stage (jellyfish)

B. Stinging Cells

• 1. Cnida—stinging organelle within a cnidocyte–Used for prey capture & defense

• nematocysts —are discharged

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B. Stinging Cells

• 2. Dangerous species– (Physalia physalis) Portuguese man-of-

war (painful stings)– (Chironex Fleckeri) box jellyfish (can kill

within 3-20 minutes)

C. Types of Cnidarians

• 1. Hydrozoans (class Hydrozoa)– a. mostly colonial– b. colonial forms contain 2 types of polyp:

• feeding polyp—functions in food capture• reproductive polyp—specialized for reproduction

– c. hydrocorals secrete a calcareous skeleton • e.g. (millepora sp.) fire coral

– d. some produce floating colonies• e.g. (physalia physalis) Portuguese man-of-war

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Types of Cnidarians

• 2. Class Scyphozoa–a. true jellyfish

• medusa is predominant life stage• photoreceptors—sense organs that can

determine whether it is dark or light• e.g. (aurelia aurita) moon jelly

• 3. Class Cubozoa• tropical• voracious predators, primarily of fish• e.g. (Chironex fleckeri ) australian sea wasp

Types of Cnidarians• 4. Class Anthozoa

–a. sea anemones• polyps with a vascular cavity divided into

compartments radiating from the central one• though sessile, many can change locations

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Types of Cnidarians

• Anthozoans continued…–b. coral animals

• polyps that secrete a hard or soft skeleton• form reefs along with types of algae

Types of Cnidarians

• Anthozoans continued…–b. soft corals

• polyps that form plant-like colonies

Ptilosarcus gurneyi

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D. Nutrition and Digestion

• 1. Gastrovascular cavity—central cavity where cnidarians digest their prey

• 2. Many hydrozoans and anthozoansare suspension feeders

• 3. Some jellies and box jellies eat fish and larger invertebrates

• 4. Sea anemones generally feed on invertebrates

E. Reproduction

• 1. Hydrozoans–generally exhibit asexual polyp stage and

sexual medusa stage in the life cycle– reproductive polyps form medusa-like

buds which grow into adults after release–adults release gametes into the water,

where they are fertilized and form larvae• planula larva—planktonic larva that grows in

the water column, then settles

E. Reproduction

• 2. Scyphozoans–medusae (sexual stage) release gametes

into the water for fertilization–planula larvae settle, grow into polyps,

and reproduce medusa-like buds asexually

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E. Reproduction

• 3. Anthozoans–asexual reproduction

• pedal laceration—leaving parts of the pedal disk (base) behind to grow into new animals

• fission—the anemone splits in two and each half grows into a new individual

• budding produces large colonies of identical hard corals

– sexual reproduction• larval stage is a planula larva

F. Ecological Relationships of Cnidarians

• 1. Predator-prey relationships–cnidarians are predators– stinging cells discourage predation

• 2. Habitat formation–coral polyps form complex 3-dimensional

structures inhabited by thousands of other organisms

–coral reefs provide a solid surface for attachment, and buffer waves and storms

F. Ecological Relationships of Cnidarians

• 3. Symbiotic relationships–Portuguese man-of-war and man-of-war

fish– reef-forming corals and zooxanthellae– sea anemones...

• and clownfish• and the hermit crab

http://www.imagequest3d.com/pages/articles/articleofmonth/slapunhappy/j003_jpg.jpg

Ctenophores

• 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–bioluminescent

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Beroe spp.

oceanexplorer.noaa.gov

Pleurobrachia spp.

d.wrobel

http://www.gso.uri.edu/phytoplankton/mnemiopsis.bmp

Ctenophores

• Digestion and nutrition–carnivorous, feeding on other planktonic

animals–may used branched tentacles in a net

pattern, adhesive cells, jellyfish stingers

Ctenophores

• Reproduction–almost all are hermaphroditic– fertilization may be in the water column,

or eggs may be brooded in the body–cydippid larva—free-swimming larva

resembling the adult ctenophore