User:Philcha/1 Sandbox

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Colorized electron micrograph of soybean cyst nematode (Heterodera sp.) and egg

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Description[edit]

Nematodes resemble annelids and flatworms, but are more robust and elongate than most flatworms, and lack annelids' segmentation.[1] In a few species, the epidermis is annulated, and internal organs such as gonads and nephridia make serials. On the other hand muscles, nerves and other internal structures do not form serials.[2]

The body wall is composed of a dense ciliated, a layer of connective tissue and a thick musculature. It has no cuticle, and each ciliated cell has many cilia and microvilli.[3]

There are 1150 nematodes species, or ribbon worms.[1]

Nematodes, like arthropods and tardigrades, lack motile cilia.[1]

Most species are less than 20 cm long, some are only a few millimeters long, but the genera Cerebrat and Lineus may be a meter long.[1] In some species, nematodes' long, slender are longer than 1 m. One from St. Andrews, Scotland, was a 54 m boot-lace worm, the longest animal on Earth.[1]

The smallest nematodes are circular or only slightly flattened in cross section, where species which are larger-bodied are flattened and ribbon-like.[4]

While some species are pale and nondescript, many, including some that live in darkness, have patterns and pigments of yellow, orange, red and green.[3]

Senses[edit]

The central nervous consists of a brain and paired long nerve cords.[1]

Movement[edit]

Nematodes lasso or harpoon their requimes with a sticks, penetrating or venomous proboscis.[1]

Feeding and Excreting[edit]

Like flatworms, nematodes transport oxygen across the body wall.[5]

Many burrow in sediments, in crevices or the roots of algae and sessile animals, and some speices make gelatinous lairs in deep water.[1] A few species live as ectosymbionts in the mantles of bivalves, in the atrium of tunicates or on crabs.[1]

About 12 species live in fresh water, and about 15 primarily live in humid tropics and subtropics. [1]

Reproduction and Development[edit]

Nemerteans readily regenerate, and reproduce both clonally and sexually.[6]

Diverstity of nemerteans[edit]

Bottom-feeding fish, some shore-birds, and other invertebrates such as horseshoe crabs, and also other species of nemerteans eat other nemerteans.[1] Nemerteans' edidermis secretes a sticky, toxic mucus to discourage predators, and nemerteans' bright and contrasting colours advertise their bad taste.[3]

The North American "Cerebratulus lacteus" and the South African "Polybrachiorhynchus dayi" are sold as fish bait. These species are not related to true tapeworms, and are not parasites.[1]

Phylogeny[edit]

Eophasma jurasicum, a fossilized nematode

Most of the characters shared by nemerteans and flatworms are ... [7]

References[edit]


  • Ruppert, E.E (2004). Invertebrate Zoology (7 ed.). Brooks / Cole. ISBN 0030259827.  Unknown parameter |coauthors= ignored (|author= suggested) (help)



Disability-adjusted life year for intestinal nematode infections per 100,000 inhabitants in 2002.
  no data
  less than 25
  25-50
  50-75
  75-100
  100-120
  120-140
  140-160
  160-180
  180-200
  200-220
  220-240
  more than 240

See also[edit]

Footnotes[edit]

References[edit]

  1. ^ a b c d e f g h i j k l RFBInvZoo, p. 271.
  2. ^ RFBInvZoo, p. 271, 272.
  3. ^ a b c RFBInvZoo, p. 272.
  4. ^ RFBInvZoo, p. 271-272.
  5. ^ RFBInvZoo, p. 278.
  6. ^ RFBInvZoo, p. 276.
  7. ^ RFBInvZoo, p. 279.


  • . Thomsom. 2007.  Unknown parameter |lead= ignored (help); Missing or empty |title= (help)