In Kingdom Animalia there are 3 phyla: Platyhelminthes – flatworms (Gk) plati – flat

helminth - worm

Nematoda – roundworms, nema (Gk) "thread"

Annelida – segmented worms, anellus (Latin) "little ring

Worms

• Specialized Tissues• Flatworms are Protostomes. What is that?• Nematodes and Segmented worms are Deuterostomes. What is that?

• Bilateral symmetry• Heterotrophic, ( Gk. - different nutrition)• Eukaryotes that have sexual reproduction. • Some can reproduce by binary fission, as in the flatworm.• Sexual reproduction increase variability and thereby increase a species chances for survival against pathogens or changes in environment. • They have a CNS!• They have an excretory system• They have a coelom or body cavity• Circulatory system• Flatworms and Nematodes--no!• Annelids—yes! • They have a muscular system (they actively move-are motile)

 

Protostome – (first mouth) In embriological development, the mouth develops first. They have a true body cavity. Includes annelids, mollusks and arthropods.

Deuterostome - (second mouth), In embriological development, the anus develops first. They have a true body cavity also but they include echinoderms, hemichordates and chordates, (us).

•Some are predators that actively hunt, others are free-living detritivores that eat detritus and micro-organisms• few are sessile filter-feeders•others are parasites•Some are serious pathogens, others are extremely beneficial in their environment. •Most must have some type of aquatic environment to live or complete some stage of their life cycle•Worms are, in general, the favorite accessory to a fishing hook as most larger aquatic predators find them very appetizing

 

•Turbellarians•Planarians•Flukes•Tapeworms

Phylum: Platyhelminthes- flatworms

http://www.youtube.com/watch?feature=player_detailpage&v=9MxI2bMwFNE

tapeworm

turbellarians http://www.youtube.com/watch?feature=player_embedded&v=HekwSO6dBG0

flukes http://www.youtube.com/watch?feature=player_embedded&v=ihxiDdQJ_iY

Platyheminthes: Beginning with flatworms, from the Gk. for “Flat” (platy, as in plate) and worm- “helminth”. These have no coelom! Most marine flatworms are 2-3 cm long. http://www.rzuser.uni-heidelberg.de/~bu6/Introduction03.html

 It is important to know the coelom because flatworms do not have one, yet roundworms have a semi-coelom, and the segmented worms have a true coelom! All other organisms higher that segmented worms have coeloms.

 

 

Define coelom:

This is a fluid-filled cavity that lies between the inside of the mesoderm lining and the outside of the endoderm lining. In other words, it is the space within a body that carries the organs and internal connective tissue. 

The flatworms by extending their pharynx out through their single opening! When they detect food they actively wrap themselves about it and out goes the pharynx, looking like a stomach being everted and secreting digestive juices. It is a sticky, organ that protrudes from the ventral side of the worm. Then, the pharynx/stomach retracts back into the body cavity and the food is absorbed into the body. Whatever is not digested is ejected through the mouth/anus.

These organisms have a ladder-like network of nerves that form a CNS; they can detect light and dark (withy their eyespots) . A nerve cord runs from anterior to posterior. Auricles are sensory organs that detect their environment, causing the animal to respond. The two rails of the ladder of nerves end at the anterior end with two brain-like ganglia.

 

They excrete wastes such as ammonia and CO2,

these have specialized cells that connect to pores in the side near the posterior end that create currents within the body to push waste materials out through the pores. 

[see webpage http://www.mcwdn.org/Animals/Flatworm.html Take the Flatworm Quiz from this page! for an overview of organism; the “video” link from that page is for this Youtube link showing marine flatworm movement: http://www.youtube.com/watch?feature=player_embedded&v=zCH37KI_R_E

https://www.youtube.com/watch?feature=player_detailpage&v=kUsQO5hx3DQ

Phylum: Nematoda

https://www.youtube.com/watch?feature=player_detailpage&v=HOaZCkA8Zvk

NematodesTrichinaFilariaHeartworm

Nematodes

http://www.youtube.com/watch?v=NNq6dKguwNU&feature=player_embedded

hookworm

http://www.youtube.com/watch?feature=player_embedded&v=dnWwHthkGkY

filariasis

http://www.youtube.com/watch?feature=player_embedded&v=_YbLZzMS9dE

Trichinosis

Nematoda: The Roundworms! Gk. nemat means “thread”; “oda” means “like”

 These are similar to flatworms in that they have no circulatory system and they have a simple coelom. However, in a major step forward for personal hygiene, these have an anus! The complex mouth of the nematode, or roundworm, allows it to perforate tissues and become parasites or pathogens of animals and plants. They are also predators of bacteria—if one can actually be a predator of bacteria!—and almost all must have water or other fluid in order to move about. Some are predators of other nematode species. These can be serious disease-causing organisms but the vast majority is beneficial or is free-living.

 

Roundworms

 Body plan is a semi-coelom—it is a cavity with a digestive tube in the center but the cavity but not filled with a circulatory system, only fluids. Muscles surround the cavity and are attached to the ectoderm, or dermis layers on the outer surface.

 It is a sexual organism with separate male and

female members, this being called dioecious.

They have a sort of internal fertilization and most

lay eggs.

 Roundworms range in size from microscopic to a few mm long, to a few parasitic species being several cm long Dirofilaria, the heartworm of dogs being one that can grow to 30 cm long; Ascaris, the intestinal roundworm, is of similar length.) For the basics of Nematoda, see here: http://www.mcwdn.org/Animals/Roundworms.html; Marine nematode video: http://www.youtube.com/watch?feature=player_embedded&v=tp-O3LME3OU ]

Class: Oligochaeta•Earthworms

Class: Polychaeta•Sandworms/Tubeworms

Class: Hirudinea•Leeches

Phylum: Annelida

Annelida are the segmented worms—the term is from Gk. meaning “rings” (anillo in Spanish is “ring”).

These are sexual worms with bodies neatly arranged in muscular, complex segments. They have a coelom. and a closed circulatory system complete with a heart and blood vessels; they also have a really complex gut from labia through to an anus.

 Many inhabit aquatic environments and some have adapted mandibles and proboscii to catch prey. Others are free-living, obtaining nutrition from benthic sediments and the micro-organisms on the water body’s floor. They are in freshwater, the ocean, the soil, mud and even birdbaths.

They have setae, bristles to grip the mud, and some are adapted into stinging cells

They have a digestive system, a mouth, pharynx, esophagus, a gizzard (where small stones aid in grinding food), a stomach where food is exposed to acids and enzymes, an intestine and an anus.

Polychaetes are sandworms and many inhabit marine littoral environments. They are predacious organisms that burrow into sand as well as swim. Marine sandworms live in sandy beach environments: http://www.youtube.com/watch?v=edKZSRQFQqY

see video: http://www.youtube.com/watch?v=S3US_Qi1-fA ; freshwater Texas polychaete: and leeches:

Segmented Worms

http://www.youtube.com/watch?v=wl7REIufCtE&feature=player_detailpage

Tubeworms are interesting organisms that inhabit benthic sites. These form tubes that are concreted or cemented from various substances secreted by the worms. These are filter-feeders and can be quite beautiful and graceful. [see videos http://www.youtube.com/watch?v=kI oN2PCvL4o and

https://www.youtube.com/watch?v=2FFnrW_SUdM

Tubeworms

Flatworms Roundworms Segmented worms

Circulatory system

No No Yes

CNS Simple/ganglia 2 nerve chords Simple brain/n. chord

Excretory system Through pharynx Anus & excrete tubes

Anus/nephridia

Both sexes No Yes Hermaphrodites

Reproduction Binary fission Sexually Other worms fertiliz

Symmetry Bilateral Bilateral Bilateral

Coelom (body cavity)

No Semi-coelom Complete

Muscular system 2 layers under skin

2 layers under skin Two sets; elongate / gather

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