phylum: nematoda - canyon crest academy library media …teacher.sduhsd.net/lolson/ap...
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Phylum:Nematoda
& Rotifera
Presented by:
Kyle Kim & Peter Chu
March 2010
Olson: Period 6http://ucdnema.ucdavis.edu/imagemap/nemmap/ENT156HTML/slid
es/fromWWW/aschelm/nematode.jpg
http://www.biology.qmul.ac.uk/research/staff/s-
araya/keratelljoke2.GIF
http://img.medscape.com/pi/emed/ckb/emergency_medicine/756148-780913-
788398-1725373.jpg
Sample Animals Free-living species
Caenorhabditis elegans
▪ Excellent model organism to
study biological phenomena
Parasitic species
Ascaris lumbricoides
▪ Responsible for the most
common intestinal worm
infection ascariasis
Kyle Kim
http://biology.unm.edu/ccouncil/Biology_203/Images/SimpleAnimals/Pseudocoeloma
te.JPG
Body Cavity
Pseudocoel
Contains the flattened gut and various reproductive organs
Enclosed by a body wall containing longitudinally-arranged muscles
Filled with pseudocoelomic fluid maintained under positive pressure
Kyle Kim
Body Symmetry• Head
– Radially symmetrical
• Many planes divide organism into two mirror images
• Body
– Bilaterally symmetrical
• Single plane divides organism into two mirror images
Kyle Kimhttp://www.utm.edu/departments/cens/biology/rirwin/Radbilatesym.gif
http://www.cartage.org.lb/en/themes/sciences/zoology/biologicaldiverstity/AnimalsI/
nematode.gif
Nervous System• Ganglial
• Cerebral ganglion (“brain”)
– Anterior neural ring with most
of the sensory nerve bodies
• Two main longitudinal ganglial
chords
– Dorsal
– Ventral
Kyle Kim
Circulatory SystemERROR 404
PAGE NOT FOUND!
• No special system
• Fluids circulated in pseudocoelom by body movements
Kyle Kim
http://www.rock-hill.k12.sc.us/schools/middle/slms/Digestiv
e_AH4/nematode-digestive.gif
Digestive System• Complete digestive tract with
specialized regions
– Anterior mouth
– Muscular and glandular pharynx (esophagus)
– Long, straight midgut (intestine)
– Rectum
– Ventral anus
• Secretion of digestive enzymes by phanyngeal glands
• Absorption of nutrients through microvilli of midgut cells
Kyle Kim
Excretory System
• canal along each side of body regulates nutrients and waste content
• excretes nitrogenous waste in the form of ammonia through body wall
http://www.wormatlas.org/hermaphrodite/excretory/Images/ExcFIG1lr.jpg
Peter Chu
Locomotion/Musculature
• long muscles under the cuticle, aligned longitudinally under the epidermis, side-to-side movement only (no crawling or lifting itself); free swimming looks like it is thrashing about aimlessly
• muscles activated by two nerves, one along ventral (belly) and one along dorsal (back)
http://classes.seattleu.edu/biology/biol235/hodin/nematodePriapulidGroup/images/NematodeLocomotion.gif
Peter Chu
Skeletal Type
• the cuticle is the closest thing Nematodes have to a skeleton
• functions as support and a leverage point for movement
• fluid in pseudocoelem serves as hydrostatic skeleton
http://www.pnas.org/content/104/44/17376/F1.large.jpg Peter Chu
Sensory Structures/Features• the epidermis consists
of a mass of cellular material and nuclei without separate membranes; secretes thick cuticle that is tough, yet flexible
• the cuticle is periodically shed; up to 4 times before adult stage
http://www.ucmp.berkeley.edu/phyla/ecdysozoa/nematoda.htmlPeter Chu
Reproduction• Nematodes are sexual animals
• the male is generally slightly smaller than the female, which usually displays a bent tail
• Nematode reproduction in free-living specimens is a very interesting process involving six stages including an egg stage, four larval stages (L1, L2, L3, L4), and an adult stage.
Peter Chu
http://kentsimmons.uwinnipeg.ca/16cm05/16labma
n05/lb5pg9.htm
More Reproduction…• Males are dioecious in that they can have
one or two testes and can have a variety of
accessory sex organs depending on the
species
• Females give rise to eggs that are then
fertilized and laid
• Once embryos, these eggs are mature and
hatch. After four molts, they becomes
adults capable of reproduction
• During molting, a nematode will shed its
skin in order to facilitate growth. The
third L3 larval stage is normally the
infectious stage for parasitic nematodes
http://www.personal.psu.edu/ncj111/Unique%20Features.htm Peter Chu
Other Features…• many nematodes are
able to suspend their life processes completely when conditions become unfavorable
• resistant states in which they can survive extreme drying, heat, or cold, and then return to life when favorable conditions return
• this is known as cryptobiosis
• this feature is shared between nematodes and rotifers
Peter Chuhttp://tardigrades.net/img/kumamushi/e-cryptobiosis.gif
Oh Gosh, There’s MORE!• They live not only in almost every geographic
location on Earth, but in such extreme habitats as ice and hot springs, as well as living on or in almost every kind of animal and plant alive today.
• Free-living nematodes
– soils
– sediments, where they feed on bacteria and detritus.
• plant parasites and may cause disease in economically important crops.
• animal parasites (including humans); well-known parasitic nematodes include hookworms, pinworms, Guinea worm (genus Dracunculus), and intestinal roundworms (genus Ascaris)GRRR!!!!
http://www.wereondoodie.com/images/hookworms.jpg Peter Chu
More Cool Beans…
• There are around 12,000 species of Nematodes that have been identified, although studies suggest that there could be up to about 500,000 species.
Peter Chuhttp://www.discoverlife.org/20/q?search=Nematoda
Rotifera
Kyle Kim and
Peter Chu
They are/have… They do not have…
Bilateral symmetry Circulatory system
Pseudocoel Excretory system
Ganglial nervous system Respiratory system
Complete digestive system
Muscular layers of longitudinal fibers
Cellular epidermis with thickened cuticle
Varied reproduction
http://www.microscopy-
uk.org.uk/mag/indexmag.html?http://w
ww.microscopy-
uk.org.uk/mag/wimsmall/rotidr.html
How Quizzical…1. What ability do Nematodes have that allows them
to survive harsh conditions? (Describe, give the
term; this ability is shared with Rotifera)
2. Do Nematodes have a skeletal system? Explain and
describe. (Tricky, tricky…)
3. Unlike annelids, nematodes do not have a _____
body. (Hint: It’s an adjective)
4. How do Nematodes and Rotifera grow in size? (It’s
not like the way we plants and animals grow;
rhymes with “Pie Toe Sis”.)Peter Chu
Hallelujah, Answers!
1. Cryptobiosis allows Nematodes and Rotifera to
survive in dryness, freezing, and blistering heat.
2. No, the cuticle is the best it gets for Nematodes
when it comes to skeletal systems for support and
movement.
3. Segmented!
4. Whoa! Nematodes and Rotifera don’t divide by
mitosis. Their cells just get bigger. And bigger.
Like the steak, well done!Peter Chu