In this article we will discuss about the classification of phylum aschelminthes.
1. The nematodes are cylindrical, triploblastic roundworms, tapering at both the ends.
2. Body cavity is a pseudocoel, lies between the mesoderm and endoderm.
3. The body is generally covered with an elastic proteinous cuticle.
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4. Alimentary canal is straight with ectodermal fore and hindgut, and an endodermal midgut without any muscles or glands.
5. Sexes separate; gonads tubular and continuous with their ducts.
a. Female organs are usually paired and open by a vulva.
b. Male organ single and opens into a cloaca.
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The Phylum Aschelminthes has been divided into 17 orders of which 7 are mostly free-living, 2 are free-living or parasitic and 8 are parasitic.
Orders:
Enoploidea:
Cuticle ringed, often with bristles; anterior end bears 6 papillae.
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Examples: Anticoma, Enoplus, etc.
Dorilaimoidea:
Cuticle smooth, without bristles; anterior end with two circlets of papillae of 6 and 10 in each.
Examples: Dorylaimus, Actionolaimus, etc.
Mermithoidea:
Smooth filiform parasites occurring in invertebrates, chiefly insects; head sense organs usually reduced to 16 papillae.
Examples: Mermis, Aproctonema, etc.
Chromadoroidea:
Aquatic mematodes with smooth or ringed cuticle; usually heavily ornamented with bristles, knobs, punctuations etc. Pharynx with a posterior bulb.
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Example: Paracatithonchus.
Araeolaimoidea:
Cuticle smooth, sometimes with bristles; labial papillae present, anterior end usually with 4 cephalic bristles.
Examples: Plectus, Odontophora, etc.
Monhysteroidea:
Cuticle smooth or slightly ringed, often bristly; anterior end with 4, 6 or 8 bristles.
Examples: Siphonolaimus, Cylindrolaimus, etc.
Desmoscelecoidea:
Cuticle heavily ringed with prominent bristles throughout or, in restricted areas, anterior end with 4 bristles.
Examples: Desmoscolex, Tricoma, etc.
Rhabditoidea or Anguilluloidea:
Free-living or parasitic nematodes with ringed or smooth cuticle; pharynx with a posterior bulb and also usually with a swelling, anterior to the nerve ring.
Examples: Rhabditis, Diplogaster, etc.
Rhabdiasoidea:
Cuticle smooth, without definite pharyngeal bulb. Parasitic stage hermaphroditic or parthenogenetic. Free-living stages may develop into males and females.
Examples: Rhabdias, Entomelas, etc.
Oxyuroidea:
Pharynx with a posterior bulb, usually valvulated; females with a long pointed tail; males with one or two equal spicules.
Examples: Oxyuris, Enterobius, etc.
Ascaroidea:
Mouth surrounded by three prominent lips; pharynx without a posterior bulb; tail of females blunt, males with two spicules.
Example: Ascaris.
Strongyloidea:
Mouth without conspicuous lips, but often with leaf crowns; pharynx without a bulb. Female usually with injectors; male with a copulatory bursa, supported by muscular rays.
Examples: Ancylostoma, Strongylus, Necator, etc.
Spiruroidea:
Mouth usually with two lateral lips, sometimes 4 or 6. Pharynx without a bulb, anteriorly muscular, posteriorly glandular. Males without bursa; spicules unequal and dissimilar.
Examples: Theliazia, Rictularia, etc.
Dracunculoidea:
Without definite lips or cuticularised buccal capsule. Vulva near or anterior to the middle of the body.
Examples: Dracunculus, Micropleura, etc.
Filaroidea:
Filiform worms without lips. Buccal capsule small or rudimentary; no pharyngeal bulb; vulva anterior.
Examples: Filaria, Loa, etc.
Trichuroidea or Trichinelloidea:
Worms with fusiform anterior portion of the body. Mouth without lips. Pharynx slender, provided with a cirrus.
Examples: Trichinella, Trichuris, etc.
Dioctophymoidea:
Moderate to very long nematodes; mouth without lips and surrounded by 6, 12, or 18 papillae; pharynx elongated, without bulb. Male with a muscular bursa.
Examples: Dictyophyme, Hystrichis, etc.