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 head (scolex)
Tapeworm
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 skeleton
Define:
* 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 Larvae
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 feeders
Define:
Leech
Earthworm
Seaworm
Seaworm parapodia