Invertebrate Animal Phyla: Worms

Domain: Eukaryota

Kingdom: Animalia

Worms in general:

*Symmetry =

What are the two benefits of this kind of symmetry?

There are three Phyla of "worms"

PHYLUM PLATYHELMINTHES “flatworms”

Ex. Planaria, Flukes, Tapeworms* 20,000 species

* Can be parasitic (flukes, tapeworms) or free-living (planaria).

* 1st animals in which tissues are organized into organs and organ systems.

*No body cavity.

* Flattened body dorsal and ventral.

* Have a Central Nervous System (CNS).Define:

* Well developed muscular system.

* One opening to the gut (still). Mouth/Anus

* Parasitic worms can have life cycles with multiple hosts.

Planaria Tapeworm

Tapeworm head (scolex) Fluke

Flatworm cross Section

Fluke Life Cycles

PHYLUM NEMATODA “roundworms”

Ex. Ascaris, hookworm, heartworm

* 10,000-15,000 known species. 1/2 million estimates. Very underestimated because many are hardly seen because they are small or internal parasites.

* Most are parasitic of plants and animals. Also found in great numbers in marine sediments rich in organic matter.

*Body Cavity

* Mostly small with cylindrical bodies usually pointed at each end.

* One way digestive tract; separate mouth and anus!

* Have a hydrostatic skeletonDefine:

* Very common parasites in most marine animals—sushi

Nematodes

Ascaris

Roundworm cross section

Nematode Life Cycles

Why you don't have to worry about parasitic worms.

* Sewage treatment

* Water treatment

* Cooking meat kills cysts and eggs

* USDA inspects

* Farming regulations for raising pigs

PHYLUM ANNELIDA “segmented worms”

Ex. Leeches, Earthworm, Seaworm (Nereis)

* 12,000 species

* Body consists of similar, repeating segments.

*Body Cavity

* Hydrostatic skeleton.

* Flexibility provided by segmentation allows for efficient crawling and burrowing.

* Closed circulatory system.Define:

* Most marine worms are found in the Class Polychaeta.~Each body segment has a pair of parapodia

Function?

Segmented Worm Cross Section

* Marine worms have a ciliated, planktonic larval stage called a trochophore larva.

Trochophore larva have been studied because the mollusks also have this larval stage in their life cycle.

* Some adults are predators of small prey. Others are deposit feedersDefine:

Trochophore Larvae

Leech Earthworm

SeawormSeaworm parapodia