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

Peter Chuhttp://familypetmedicalcenter.com/medical_images/hookworms.jpg

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