Worms
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
• 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 microorganisms
• 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
Phylum: Platyhelminthes- flatworms
• Turbellarians
• Planarians
• Flukes
• Tapeworms
flukes
tapeworm
turbellarians
http://www.youtube.com/watch?featur
e=player_embedded&v=ihxiDdQJ_iY
http://www.youtube.com/watch?feature
=player_detailpage&v=9MxI2bMwFNE
http://www.youtube.com/watch?feature=
player_embedded&v=HekwSO6dBG0
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 CO 2,
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=zCH3
7KI_R_E
Phylum: Nematoda
Nematodes
Trichina
Filaria
Heartworm
Trichinosis
Nematodes
hookworm
filariasis
http://www.youtube.com/watch?feature
=player_embedded&v=_YbLZzMS9dE
https://www.youtube.com/watch?feature=pla
yer_detailpage&v=HOaZCkA8Zvk
http://www.youtube.com/watch?v=NNq
6dKguwNU&feature=player_embedded
http://www.youtube.com/watch?feature
=player_embedded&v=dnWwHthkGkY
https://www.youtube.com/watch?featur
e=player_detailpage&v=kUsQO5hx3DQ
Roundworms
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.
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 ]
Phylum: Annelida
Class: Oligochaeta
• Earthworms
Class: Polychaeta
• Sandworms/Tubeworms
Class: Hirudinea
• Leeches
Segmented Worms
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:
http://www.youtube.com/watch?v=wl7
REIufCtE&feature=player_detailpage
Tubeworms
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
Compare and Contrast
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