The Worms

Phylum PlatyhelminthesPhylum NemerteaPhylum NematodaPhylum Annelida

Bilateral Symmetry

• One way to cut and get 2 identical halves

• Front (anterior) and rear (posterior)• Back (dorsal) and belly (ventral)• More active in pursuit of prey

Platyhelminthes - Flatworms

• Dorsoventrally flattened• Simple Central Nervous system• Muscular system, Reproductive

system - True organs• Singular opening for gut

20,000 Species of Flatworms• Turbellarians - Free-living

carnivores, seen most in marine habitats

• Flukes (Trematodes) – largest group, parasites

• Tapeworms (cestodes) – live in intestines.

Ribbon Worms (Nemertea)

• Sac Gut digestive tract (mouth, gut)

• Circulatory system/Hermaphrodites

• Proboscis – used to entangle prey• Feed on worms and crustaceans

Nematodes (some – roundworms)

• Live in sediment or tissues of marine organisms (parasitic)

• Cylindrical body, pointed at both ends.

• Larva found in the flesh of many fish– Infection of humans from eating raw

or under cooked fish

Annelida – segmented worms• Includes earthworms and many

marine worms• Polychaetes – marine annelids.

– Each segment has parpodia with setae at the ends.

– Closed circulatory system– Most carnivores - Nereis

More Annelids

• Oligochaetes– Marine earthworms, found in mud and

sand

• Leeches (Hirudinea)– Most are freshwater – sucker at ends

Brachiopoda (not a worm)

• Lamp shell• Two valves,

dorsal and ventral• Lophophore,

unique feeding structure – like two ciliated, coiled arms

The Christmas Tree WormThe Christmas tree worm, Spirobranchus giganteus, is a Christmas tree-shaped serpulid tube-dwelling worm with magnificent twin spirals of plumes used for feeding and respiration. This cone-shaped worm is one of the most widely recognized sedentary polychaete worms.