Transcript Nematoda - Net Start Class

General Characteristics
 Bilaterally symmetrical, triploblastic, vermiform
(worm-like) roundworms
 Unsegmented
 Body has more than 2 cell layers
 Pseducoelmate (body cavity is a pseudocoel)
General Characteristics
 Body is round in cross section and covered with a thick
cuticle that is periodically shed as the worm grows
 Muscles are along the length of body not encircling it.
 Have no circulatory or respiratory structures
 Separate sexes, usually sexual reproduction
General Characteristics
 Nervous system with pharyngeal ring, longitudinal
nerve in epidermal cord
 Have unique cephalic sense organs (amphids), only
some have lateral, caudal sense organs (phasmids)
 Tubular digestive system that passes from mouth to
anus, one way.
 Intestines specialized and complete
General Characteristics
 Most have renette cells to conserve water; some only
have ducts
 Usually small – less than a millimeter long
 Can live almost anywhere, species can be free-living or
parasitic.
 Hydrostatic skeleton formed by pseudocoel
Classes
Adenophorea
Nematoda
Secernentea
Adenophorea
 Trichuris trichiura: whipworm
 Trichinella spiralis
 Romanomermis culicivorax
 Xiphinema index: Dagger nematode
http://ucdnema.ucdavis.edu/imagemap/nemma
p/ent156html/slides/fromCD/0847/026B.GIF
http://ucdnema.ucdavis.edu/imagemap/nemma
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Secernentea
 Caenorhabditis elegans C.
Elegans “The Worm”
 Enterobius vermicularis:
pinworm
 Ancylostoma duodenale:
oldworld hookworm
http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156h
tml/slides/fromWWW/hook/hookfila.jpg
http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156h
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Body Plan
 Bilaterally symmetrical,
unsegmented worms.
 They are covered with a
flexible and thick cuticle,
that is shed as the worm
grows.
http://www.kent.k12.wa.us/staff/neilcochran/APBio
Documents/ch26_lecture.ppt#306,54,Phylum
Nematoda: Roundworms
Body Plan continued
 Muscles under the epidermis extend the length of the
body rather than encircling the body.
 They have a hydrostatic skeleton.
 They have a pseudocoel which separates the
endoderm-lined gut from the rest of the body.
http://plpnemweb.ucdavis.edu/nemaplex/images/metazo12.jpg
Feeding
 Near mouth there are
usually 16 hair-like sensory
organs.
 The mouth is often
equipped with piercing
organs called stylets - sharp
spikes used to kill cells or
move through the dirt
http://www.cpes.peachnet.edu/nemabc/_borders/Pred._dorylaimi
d.jpg
Feeding continued.
 Food passes through the mouth as a result of the
sucking action of a muscle chamber called the
pharynx.
 Food then goes directly to the digestive tract,
where it broken down and nutrients are absorbed.
 Digestive tract connects directly to the anus.
 Many nematodes are parasites.
Respiration
 Breathe by simple diffusion.
http://www.dkimages.com/discover/previews/740/48842.JPG
Circulation
 No circulatory system
 Foods circulate in pseudocoelem through body
movements
Excretion
 Have excretory ducts that
permit them to conserve H20
and live on land
 Unique excretory system of
collecting tubules or renette
cells (excretory glands)
 Nitrogenous waste is excreted
in the form of ammonia
through the body wall
 Excretory system, if present,
empties through an anterior,
ventromedial porus.
Renette Cells
Response
 Have a nervous system with
pharyngeal nerve ring
 Unique cephalic sense organs,
amphids
 Some with caudal sense
organs, known as phasmids
 The muscles are activated by
two nerves that run the
length of the nematode on
both the dorsal (back) and
ventral (belly) side
Response
 At the anterior end of the animal, the nerves branch
from a dense circular nerve ring surrounding the
pharynx, and serving as the brain.
 Smaller nerves run forward from the ring to supply the
sensory organs of the head.
Response
 The body of nematodes is covered in numerous
sensory bristles and papillae that together provide a
sense of touch.
 Behind the sensory bristles on the head lie two small
pits, or amphids.
Movement
 Nematodes move by
undulations or wave-like
motions of the body.
 The muscles are able to
“manipulate” each other to
contract/relax accordingly
Movement cont.
 There are the four "fields" of longitudinal muscles.
 Because the pseudocoelomic fluid is incompressible,
the internal pressure increases causing stretching of
muscle cells in another part of the body.
Movement cont.
 Through this system of local contractions of the
muscle fields the dorsal and ventral longitudinal
musculature act as antagonists, producing sinusoidal
waves along the length of the nematode's body.
 Most nematodes lie on their sides and the resulting
dorsi-ventral undulations move the nematode in the
horizontal plane through an aquatic medium
Reproduction
 Basic male reproductive
structures include:
 One
 Seminal vesicle - sperm
accumulate here
 Vas deferens opening into a
cloaca
 Bursae - thin cuticle extensions
 Spicules
 Basic Female
reproductive structures:
 one or two ovaries
 seminal receptacles
 Uteri
 ovijector
 vuvla
Reproduction
 All nematodes lay eggs
 Syngamy, or cross fertilization, is common in most nematodes.
 Hermaphroditism can occur
 Parthenogenesis is also a normal means of reproduction in some
nematodes.
 Unique to animal kingdom, nematodes produce ameboid sperm allows sperm to crawl to ova against hydrostatic pressure
 Internal fertilization
 Dioecious
Works Cited
 Lower Metazoan Phyla. Nemaplex, University of California Davis. 15 April 2010
<http://plpnemweb.ucdavis.edu/nemaplex/Kingdoms/metazoa.htm#Nematod
a>
 Waggoner, Ben and B.R. Speer. Introduction to Nematoda. UCMP. 15 April 2010
<http://www.ucmp.berkeley.edu/phyla/ecdysozoa/nematoda.html>
 Mehaffey, Leathem. Phylum Nematoda. Biology 266, Vassar University. 15 April
2010
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<http://faculty.vassar.edu/mehaffey/academic/animalstructure/outlines/nema
toda.html>
Phylum Nemata. Biology of Parasitism – Lecture Notes, University of
California Davis. 15 April 2010
<http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/E156charac>
Raven, Robert H. and George B. Johnson. Biology. New York, NY: McGraw Hill,
2002.
Ramel, Gordon. Phylum Nematoda. Earthlife Web. 15 April 2010
<http://www.earthlife.net/inverts/nematoda.html>
Nematology Lab at UNL. University of Nebraska – Lincoln. 20 April 2010
<http://nematode.unl.edu/>