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Phylums of Worms and Phylum Mollusca. WORM PHLYA. Worms are general grouping Worms have bilateral symmetry Allows for more sophisticated behaviour Worms are the beginning of advanced inverts Evolved organs and other specialization Evolved complete digestive tracts Body cavity/ coelem

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Phylums of Worms and Phylum Mollusca

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Phylums of worms and phylum mollusca

Phylums of Worms and Phylum Mollusca

Worm phlya


  • Worms are general grouping

  • Worms have bilateral symmetry

    • Allows for more sophisticated behaviour

  • Worms are the beginning of advanced inverts

    • Evolved organs and other specialization

    • Evolved complete digestive tracts

    • Body cavity/ coelem

      • found in most bilateral animals

      • organs are suspended in this space

Worm phylas

Worm Phylas

  • Worms are soft bodied so they mostly live in tubes, burrows or under something

  • Feeding ranges from parasites to carnivorous hunters

  • Some worms create mucous nets to catch food while they are safe in their burrow

Platyhelminthes flatworms

Platyhelminthes - Flatworms

  • Advancements include…

    • Central nervous system (brain)

    • Muscles

    • Simplest of animals with bilateral symmetry

  • Three classes of flatworms

    • Turbellaria: carnivorous hunters

    • Trematodes and Cestodes which are both parasitic

Phylums of worms and phylum mollusca

Tapeworm found on Tiger sharks and mackerel.

Phylums of worms and phylum mollusca

Nemertea ribbon worms

Nemertea- Ribbon worms

  • Advancements…

    • Nervous system with a brain

    • Muscles

    • Circulatory System with blood vessels

    • Complete digestive tract (mouth and anus)

Ribbon worms continued

Ribbon worms continued-

  • Stretchy bodies (8 in can stretch to 3 ft)

  • Gather food with a proboscis that everts from inside them to catch food

  • Proboscis may be sticky or poisoned

Phylums of worms and phylum mollusca

Nematode roundworms

Nematode - Roundworms

-Body cavity

-Have to molt cuticle as they grow

-Live in sediments and tissues of orgs

-parasitic & predatory

Annelida segmented worms

Annelida – Segmented Worms

  • Head-like area with a brain

  • Segmentation- repeated compartments

    • Helps with motion

    • Allows for appendages

Phylums of worms and phylum mollusca

Class Polychaeta

  • Each segment has a flattened extension called parapodia

  • Gills for breathing

    Class Oligochaete

  • burrow in mud and sand

  • Scavengers

    Class Hirudinea

  • Live on whatever they are “eating”

  • Parastic / blood sucking

  • Sucker at each end

Phylums of worms and phylum mollusca

Phylums of worms and phylum mollusca

Sipuncula peanut worms

Sipuncula – Peanut Worms

  • Recent studies have placed them with Annelids even though they aren’t segmented

  • Bottom dwellers, many burrow

  • Deposit feeders

Phylums of worms and phylum mollusca

Echiuria sausage worms

Echiuria- Sausage Worms

Like the Peanut Worms

Pogonophora beard worms

Pogonophora –Beard Worms

  • Lack a digestive system

  • Symbiotic bacteria at hydrothermal vents provide them food

Phylums of worms and phylum mollusca

Vent community worms, live in tubes

Use bacteria in them to manufacture food

Tube worms

White Tube worm

Chaetognatha arrow worms

Chaetognatha- Arrow Worms

  • All the features of a complex org

  • Eyes and a distinct head

  • planktonic

  • vicious carnivores preying on larvae of other animals

Phylums of worms and phylum mollusca

Lophophorates…colonial worms

  • All the features of complex orgs

  • Lophophore- unique feeding structure with ciliated tentacles

    • Suspension feeders

  • Two groups-Bryozoans and Phoronids

Phylum mollusca

Phylum Mollusca

  • Evolutionary advances in specializing parts of the body

  • Advancement in the nervous system

    • Squid and octopus are as intelligent as some vertebrates

    • Allows for more sophisticated behaviors

  • Very successful phylum and one of the most diverse

Phylum mollusca1

Phylum Mollusca

  • Wide diversity of form but based on general body plan

Mollusc body plan

Mollusc Body Plan

All molluscs have or had: Foot, Mantle, Shell and Radula

Mantle – tissue which secretes shell

Bilateral symmetry

Body Cavity

Open circulatory system with compartmentalized heart (except cephalapods)

Phylum mollusca2

Phylum Mollusca

Class Polyplacophora….chitons

Phylum mollusca3

Phylum Mollusca

Class Bivalvia “two shells”

Ex. Clams, mussels, scallops

Phylums of worms and phylum mollusca

  • Figure 2 Geoduck Clams. Geoducks are a species of long-lived (100+ years) saltwater clams (Panope generosa) native to the northern Pacific coasts of Canada and the U.S. Pacific Northwest. Washington State’s Puget Sound bays and estuaries harbor the highest density of geoducks in the continuous United States (Washington Dept. of Ecology). Photo courtesy of Are Strom. Used with permission.

Phylum mollusca4

Phylum Mollusca

Class Scaphapoda…tusk shells


Phylum mollusca5

Phylum Mollusca

Class Gastropoda “stomach foot”: snails, slugs and limpets

Phylum mollusca6

Phylum Mollusca

Class Cephalopoda…squid, octopus

Shells of shellfish

Shells of Shellfish

  • Three layers: conchin, CaCO3 in conchin matrix, and nacreous made of CaCO3 with some conchin in sheet-like pattern (mother-of-pearl).

  • Wide variety of shapes.

  • Reduced shells (sea hares, squid pen, cuttle bone).

  • Lost shells (octopus, nudibranchs)

Mollusc locomotion

Mollusc Locomotion

  • Have a muscular foot for crawling, swimming, burrowing

  • Modified into tentacles for squid & octopus

    • Muscles forces water out siphon or funnel for swimming.

  • Byssal threads- protein strands used to anchor some shellfish to a surface

Sense organs

Sense Organs

Well developed nervous system in cephalopods

Chemosensory organs- sense chemicals by smell or taste

Cephalopods have highly developed eyes.

Distinct images and possibly color (1 species of squid).

Phylums of worms and phylum mollusca


Interesting characteristics

Interesting Characteristics

Color change in cephalopods using chromatophores.

Cells that contain pigments and are under nervous system and hormonal control.

Mollusc feeding

Mollusc Feeding


Used for scraping, boring, and sometime associated with toxins.



Cephalopods highly mobile predators.

Catch prey with suckered arms.

Neurotoxins associated with beak in octopus.



  • Filter feeding

  • Water comes through a siphon, passes over ctenidia, exits over anus and out exhalent siphon

  • Siphons are a flexible tube.

  • Food particles sorted by ctenidia



  • Gastropod feeding habits are extremely varied, although most species make use of a radula in some aspect of their feeding behavior.

  • Some graze, some browse, some feed on plankton, some are scavengers or detritivores, some are active carnivores.

Mollusc digestion

Mollusc Digestion

  • Complete digestive system

  • Stomach often has a crystalline style- rod with enzymes

  • Food then goes to a digestive gland and to its intestine. Waste passed through anus.

  • How do molluscs reproduce and develop

    How do molluscs reproduce and develop?

    Mollusc reproduction and development

    Mollusc Reproduction and Development

    Separate sexes and sexual reproduction

    Some lay eggs and some bear live young

    Some with internal and external reproduction

    Phylums of worms and phylum mollusca

    • Circulatory System exception

    • Cephalopods have closed circulatory system.

    • More efficient circulation which allows them to be fast hunters.

    Human and mollusc interaction

    Human and Mollusc Interaction

    • Source of food

    • Shells are a source of calcium for some birds

    • Crushed shells are used to kill agricultural pests. Mollusks also nourish humans culturally.

    • Mollusk shells served as money in some early cultures

    • Species health is used in monitoring water pollution

    • Many are invasive species

    True or false

    True or False

    • All cone shells possess a poisonous dart (their"radula"), with which they harpoon, inject venom and kill their prey. Cone shell venom is toxic enough to hurt or even kill a full-grown man!

    True or false1

    True or False

    • Most shelled molluscs can make pearls

    • They coat the foreign substance with nacre, the same as the lining of their shell.

    • Stimulus include organic material, parasites, or even damage

    • Pearl oysters take up to 7 years to grow pearls big enough for jewelry.

    True or false2

    True or False

    • The largest known bivalve was a  "Giant Clam" (Tridacna gigas which weighed in at an amazing 734 pounds (333kg!!) and was nearly four feet  (1.4m!!) in length. 

    • It can swallow a diver

    True or false3

    True or False

    • The blue-ringed octopus is currently one of the most toxic known sea creatures, next to the box jelly

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