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Phylums of Worms and Phylum Mollusca

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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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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

Tapeworm found on Tiger sharks and mackerel.

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

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

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

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

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

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
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

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).

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


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