Transcript Annelida - Net Start Class

Annelida
Annelida General Info
Segmented worms
 Contains 3 classes
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– Polychaeta
– Oligochaeta
– Hirudinea
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Triploblastic protostomes with a
coelom, closed circulatory system, and
true segmentation
Class Polychaeta
http://www.ucmp.berkeley.edu/annelida/polyintro.html
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Called: lugworms, clam worms, bristleworms, fire
worms, palolo worms, sea mice, featherduster
worms
They look the most diverse of the classes of
Annelids
Some have fine, barbed hairs that will embed in
skin if you touch them
Each body segment has a pair of fleshy protrusions
called parapodia that bear many bristles, called
chaetae, which are made of chitin.
http://romunov.blogsome.com/images/ol
igochaeta.jpg
Class Oligochaeta
Earthworms
 Eats its weight in soil each day
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– Suck in organic and other material by
expanding pharynx, grinding up soil in the
gizzard
Hermaphroditic-they use copulation
 No eyes because they live
underground
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Class Hirudinea
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Leeches
Inhabit fresh water for the most part, some
tropical
Flattened dorsoventrally (like a flatworm)
The coelom is not divided, unlike
Oligochaeta and Polychaeta.
All have evolved suckers on one or both
ends, some have evolved the ability to suck
blood
– Parasitic
This is the picture from the
Bio Book
Body Plan
3 body regions-prosomium, trunk,
pygidium; head, thin body, small tail
 Average length 1.36
 Bilateral
 Metameric (segmented)
 Cylindrical body
 Have a coelom
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Feeding
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Wide range
Detritus and algae; eat decomposing
organic material, small organisms, and soil
particles
Ingest soil-increases rate of the nutrient
cycle
Castings-pass out what they don’t need
(earthworms)
Filter feeders, scavengers
Complete digestion, extracellular, have a
mouth and anus
Respiration
Not true respiratory organs
 Diffusion, respiration can occur directly
through body walls
 Cutaneous (occurs due to rich
vascularity under epidermis) or
branchial
 Gills if aquatic
 vascular
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Circulation
True closed circulatory system-blood
circulates with in blood vessels and
through heart
 May have several hearts
 First to have closed system, makes
pumping more efficient
 Blood usually contains hemoglobin
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Excretion
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Use nephridia: coiled tubules with an expanded funnelshaped nephrostome for excretion
The nephrostome is attached to the septum dividing two
segments and opens into the anterior segment. The
tubule opens to the outside.
Filtration of the blood across the tubule wall occur
through diffusion
Most annelids have metanephridia which depend on filter
cells to filter blood twice
Primitive annelids have protonephridia which perform two
filtrations
Aquatic annelids excrete ammonia
terrestrial annelids excrete urea
http://infusion.allconet.org/webquest/annelida.html
Response
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Simple brain located in the anterior end
Ganglia: nerve cell bodies, located in every
segment
One ventral nerve cord runs the length of
the body connecting to the brain and paired
ganglia of each segment
Sense light, moisture, chemicals, and
physical stimulation
Some have eyes (polychaeta)
http://tolweb.org/articles/?article_id=57
Movement
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Hydrostatic skeleton-flexibility
Annelids contract various muscle groups around
the segment that elongate one segment at a time.
Then they contract muscles along the length to
move forward
Terrestrial annelids have setae: chitin that help
anchor them to the ground
Movement:
– crawl using parapodia- outgrowths that look like bristles
(lugworms)
– Swim (leeches)
– Crawl by folding segments (like earthworms)
Reproduction
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Asexual Reproduction:
– Budding: an outgrowth of the parent
separates to form a new individual (not
similar size)
– Fission: parent separates into two or
more individuals of equal size
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Sexual Reproduction (following
slides)
Polychaeta Sexual
Reproduction
External fertilization in water
 Lack gonads
 Result in ciliated trochophore larvae
 Swarming occurs in some speciesindividuals join together to release
sperm and/or eggs
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Oligochaeta Sexual
Reproduction
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Hermaphroditic
reproduce sexually by reciprocal fertilization
where partners exchange sperm by joining
their anterior ends during mating
After mating, the oligochaeta produces
cocoons that take up eggs which are then
fertilized by the sperm
Young worms hatch from cocoon (no larvae)
http://image.tutorvista.com/content/diversity-living-world/earthworm-structure.jpeg
Works Cited
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"All Tropical Fish - Bristleworms Class: Polychaeta." All Tropical Fish - Marine Fish,
Corals, Invertebrates and Freshwater Fish. Web. 20 Apr. 2010.
<http://www.alltropicalfish.com/content/view/137/101/>.
"The Annelids (Phylum Annelida)." The Earth Life Web. Web. 20 Apr. 2010.
<http://www.earthlife.net/inverts/annelida.html>.
“Annelids-Easy Review.” Biology Questions. Web. 19 Apr. 2010. <http://www.biologyquestions-and-answers.com/annelids.html>.
“Annelida-Worms and Leeches.” CSIRO Entomology Home. Web. 19 Apr. 2010.
<http:www.ento.csiro.au/education/allies/annelida.html>.
"Introduction to the Polychaeta." UCMP - University of California Museum of
Paleontology. Web. 20 Apr. 2010.
Ramel, Gordon. “The Annelids (Phylum Annelida).” The Earth Life Web. Web. 19 Apr.
2010. <http://www.eart5hlife.net/inverts/annelida.html>.
Raven, Peter, and George Johnson. Biology. 6. New York, New York: McGraw-Hill, 2002.
906-909. Print.
Rouse, Greg W., Fredrik Leijel, and Damhnait McHugh. 2002. Annelida.
<http://tolweb.org/Annelida>.