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06 BENTHOS. I.Sponges (Phylum Porifera) A.Evolutionary history 1.Fossil sponges are some of the oldest known multi-celled animals . Fossil Sponge Showing a Honey-combed Pore Pattern. Fort Scott Limestone in Bourbon County, Kansas. A.Evolutionary history (continued)

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  • I.Sponges (Phylum Porifera)

  • A.Evolutionary history

    • 1.Fossil sponges are some of the oldest known multi-celled animals

Fossil Sponge Showing a Honey-combed Pore Pattern

Fort Scott Limestone in Bourbon County, Kansas.

A.Evolutionary history (continued)

2.In phylogenic studies, sponges have been treated as a sister group to the other animal (= Metazoa) taxa.

  • Evolutionary history

  • 3.Recent genetic evidence, however, suggests that the ctenophores may have separated from the other animals before the sponges

Major events of loss and gain in the evolution of early animal tissue complexity are suggested by the analysis of the first representative genome from the ctenophore phylum


  • I.Sponges (continued)

  • B.Body parts

    • Epithelial cells only (no muscle, connective, nor nervous tissue)

    • Structural protein SPONGIN

  • (1)Coarse collagen fibers

  • (2)Responsible for resilient and absorbent properties of sponge skeleton

Spongin Fibers


B. Body Parts of Sponges (continued)


a.Deposits of…

(1)Calcium carbonate


b.Function to…

(1)…provide structural strength especially in narrow passageways

(2)…inhibit predation

Spicules from an Hexactinellid Sponge

Figs. 5-9A & B, p. 84

Spicules from modern sponge

Magnification = 100X


Spicules from a Fossil Sponge Stained Orange by Iron Oxide

Lower Ordovician, Idaho


I.Sponges (continued)

C.Rely upon currents to filter-feed

C.Filter-feeding currents (continued)

1.Water flow

a.Enters through external pores into small passageways known as CHOANOCYTE CHAMBERS

(1)Lined by cells called CHOANOCYTES

(2)Food particles are captured

b.Processed water enters a CENTRAL CAVITY

c.Waste water leaves via openings called OSCULA [= little mouth; osculum = sing.]

Central Cavity

Central Cavity

Arrows show locations of oscula

Summary of Filter-feeding in Sponges

C.Filter-feeding currents (continued)

2.Control of feeding currents

a.Some sponges can pass their own weight in water every 5 seconds

Cheap Thoughts


Jack O’Brien

How does an organism with no muscles “pump” water through its body?

2.Control of feeding currents (continued)


(1) A decrease in the X-sectional area of a pipe causes an increase in the velocity of a liquid flowing through that pipe (river moves slowly in wide portions of a canyon and rapidly in a narrows)

(2)The volume of a fluid passing by any point remains the same, so a decrease in the X-sectional area at a point results in an increase in flow

The relationship between the area of a tube and the velocity of a non-compressible fluid passing through that tube. (The lengths of the arrows labelled v represent relative velocities of the fluid.)



(3) Since the X-sectional areas of all the choanocyte chambers is greater than the area of the osculum…

(a)…the speed of the water current leaving the sponge at the osculum is greater than the speed of the water currents entering pores and the choanocyte chambers

(b)…waste water is carried away from sponge

More Cheap Thoughts


Jack O’Brien

Why don’t algae, barnacles and other encrusting or fouling agents grow on sponges?



Sponges apparently use

“chemical warfare”

Science 2008, 320: 1030

Science 2008, 320: 1028

Currently there are numerous pharmaceutical companies sponsoring research on chemicals produced by sponges and their symbionts looking for medicinal properties.

This includes Johnson & Johnson original support of the Harbor Branch Oceanographic Institute in Ft. Meyers, FL now affiliated with Florida Atlantic University

The deep-water submersible Johnson-Sea Link


Florida Keys

Photo: J. O’Brien, 2011


Photo: J. O’Brien, 2011

Large Barrel Sponge

Photo: J. O’Brien, 2011

  • II.Mollusks

    • A.Adults lack obvious segmentation

    • B. Specialized structures

      • 1.RADULA

  • a.Rasping tongue-like structure

  • b.Can bore holes in prey or scrape algae from rocks

  • cPossesses a hhardness value of 6 on the Mohs scale

  • (1)Diamond hardness is 10

  • (2)Harder than poor grades of steel

  • EM of


    • Specialized structures (continued)

    • 2. Muscular FOOT

      • a. Movement

      • b. Attachment (limpets & abalone)

      • 3. Calcareous SHELL

      • 4. MANTLE

      • a.Thin layer of tissue under shell

      • b.Lays down shell

      • c.Respiratory organ

    Keyhole Limpet with Mantle Covering External Shell

    • Specialized structures (continued)


      • a.Space between mantle & body organs

      • b.Location of GILLS

      • c.Inhalant and exhalant feeding currents

      • move through it

    II. Mollusks (continued)

    C.Most marine mollusks have a TROCHOPHORE larva that develops into a VELIGER

    Castro & Huber

    2003, p. 332


    Found in Annelids and Mollusks

    • D.Gastropoda

      • 1.Most diversified molluscan class (35,000 species)

      • 2.OPERCULUM

        • a.On coiled shelled gastropods

        • b.Hard plate that covers aperture when foot withdrawn

        • c.Functions

        • (1)Protection

        • (2)Prevents desiccation

    Operculum of a Whelk


    • D.Gastropoda (continued)

    • 3.Neogastropods

      • a.Characteristics

        • (1)Extendible BUCCAL TUBE or PROBOSCIS (snout) with mouth at end

        • (2)Portion of mantle forms a SIPHON

        • (3)Shell has a SIPHONAL CANAL

    • Neogastropods (continued)

    • Examples

    • (1) Whelks common in seagrass habitats

    Siphonal Canal


    Buscyon, Lightening whelk feeding on a bivalve

    Lippson & Lippson, 1984, Life in the Chesapeake,p. 53

    Whelk egg string

    Photo: J. O’Brien 2013

    Common whelklaying eggs

    Picture: Ron Offermans http://molluscs.at/gastropoda/index.html?/gastropoda/sea/common_whelk.html

    Coral Reef Gastropods

    Photo: J. O’Brien, 2011

    Conchs in a Boat

    Photo: J. O’Brien, 2011

    Conchs on a Shelf

    Photo: J. O’Brien, 2011

    Conchs in Space

    Photo: J. O’Brien, 2011

    • Examples of neogastropods (continued)

    • Cone Shells

    • (a)Predators on tropical reefs

    • (b)Teeth of radula are harpoon-like

    • (c)Contain venom

    • (d)Stabbed into prey by proboscis

    Cone Shells with Names Carved into Shell

    Photo: J. O’Brien, 2011



    a.Shell formed of two valves

    b.LIGAMENT acts to spring open valves

    c.Large powerful ADDUCTOR MUSCLES close valves

    (good tasting)

    Clam and Mussel

    Painting by Georgia O’Keefe, 1926

    • Bivalves (continued)

    • Filter-feeders

    • a.Gills covered with mucus

    • b.Trap suspended particles (= plankton)

    • c.Cilia carry food to mouth


      • (1)Reject unsuitable food

      • (2)Form PSEUDOFECES

    • Bivalves (continued)

    • Life-styles

    • a.Most bury in unstable substrates

    • b.Dig by contracting valves and moving foot

    • c.Siphon extends up into water column


    • Bivalves (continued)

    • 4.Mussels

    • a.Attach to firm substrates with BYSSUS THREADS

    • b.Mytilus edulis

    • (1)Edible mussel

    • (2)Defend themselves by pinning predatory snails with byssus threads

    Littorina, Marsh Periwinkle

    Geukensia Ribbed Mussel


    Lippson & Lippson, 1984, Life in the Chesapeake,p. 162

    • Bivalves (continued)

    • 4.Oysters

    • a.Attach with cement

    • b.Mantle secretes cement around attached valve

    • c.Smaller valve remains free

    Oyster Drill

    Oyster, Crassostrea, and Associated Mollusks

    Lippson & Lippson, 1984, Life in the Chesapeake,p. 123

    Mobile Press Register March 9, 2008

    Mobile Press Register March 9, 2008

    • Bivalves (continued)

    • 5.Shipworms

    • a.Bivalves that burrow into submerged wood

    • b.Repeated movement of rough valves erodes cavity

    • c.Destroy wharves

    Inhalent & exhalent siphons


    Shipworm removed from tunnel


    Wood damaged by shipworms


    • Bivalves (continued)

    • 6.Tridacna

    • a.“Man-eating” clam

    • b.Harbor colorful zooxanthellae

    • (= symbiotic dinoflagellates)

    • c. Biggest bivalve on tropical reefs

    Tridacna, the “Man-eating” Clam

    Tridacna, with colorful Zooxanthellae

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