general characteristics bilaterally symmetrical, triploblastic, vermiform (worm-like) roundworms...
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General CharacteristicsBilaterally symmetrical, triploblastic,
vermiform (worm-like) roundwormsUnsegmentedBody has more than 2 cell layersPseducoelmate (body cavity is a
pseudocoel)
General CharacteristicsBody 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 structuresSeparate sexes, usually sexual reproduction
General CharacteristicsNervous system with pharyngeal ring,
longitudinal nerve in epidermal cordHave 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 CharacteristicsMost have renette cells to conserve water;
some only have ductsUsually small – less than a millimeter longCan live almost anywhere, species can be
free-living or parasitic.Hydrostatic skeleton formed by pseudocoel
Classes
AdenophoreaTrichuris trichiura: whipwormTrichinella spiralisRomanomermis culicivoraxXiphinema index: Dagger nematode
http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/slides/fromCD/0847/026B.GIF
http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/slides/fromWWW/trichuris/ttrichmf.jpg
SecernenteaCaenorhabditis elegans
C. Elegans “The Worm”Enterobius vermicularis:
pinwormAncylostoma duodenale:
oldworld hookworm
http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/slides/fromWWW/cele/b0523_5_vul.jpeg
http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/upenn/oxyurisf.jpg
http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/slides/fromWWW/hook/hookfila.jpg
Body PlanBilaterally
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/APBioDocuments/ch26_lecture.ppt#306,54,Phylum Nematoda: Roundworms
Body Plan continuedMuscles 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
FeedingNear 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._dorylaimid.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.
RespirationBreathe by simple diffusion.
http://www.dkimages.com/discover/previews/740/48842.JPG
CirculationNo circulatory systemFoods circulate in pseudocoelem through
body movements
ExcretionHave 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
ResponseHave 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
ResponseAt 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.
ResponseThe 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.
MovementNematodes 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
ReproductionBasic 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 ovariesseminal receptaclesUteriovijector vuvla
ReproductionAll nematodes lay eggsSyngamy, or cross fertilization, is common in most
nematodes. Hermaphroditism can occurParthenogenesis 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 fertilizationDioecious
Works Cited Lower Metazoan Phyla. Nemaplex, University of California Davis. 15 April
2010 <http://plpnemweb.ucdavis.edu/nemaplex/Kingdoms/metazoa.htm#Nematoda>
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 <http://faculty.vassar.edu/mehaffey/academic/animalstructure/outlines/nematoda.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/>