Phylum Nematoda                                            

Rev 01/25/2022  

Adenophorea Chromadorea
Chromadoria Rhabditia Spiruria Diplogastria
  Enoplida   Araeolaimida   Rhabditida   Spirurida   Diplogastrida
  Isolaimiida   Chromadorida   Strongylida   Ascarida   *Tylenchida
  Mononchida   Desmoscolecida       Camallanida    
  *Dorylaimida   Desmodorida       Drilonematida    
  Stichosomida   Monhysterida            

Key to the Orders of Nematoda:

              (Compiled from Maggenti, 1981, and lectures by Maggenti in 1992)
1 a
Amphids always post-labial; hypodermal glands present; hypodermal cells have one nucleus; 3 caudal glands; male with 2 testes and with supplementary glands median-ventral in a single row; generally have 5 esophageal glands


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b Amphid apertures on lips, often difficult to see; no hypodermal glands; hypodermal cells are multinucleate; no caudal glands; male with a single testis and with paired pre-anal supplements, subventral in 2 rows; 3 esophageal glands Class:


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2 a Body without annules; amphid aperture not elaborate - may be large, oval, or stirrup-shaped; 5 esophageal glands Sub-class:


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b Body usually has annules; amphids elaborate, spiral; 3 esophageal glands Sub-class:


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3 a Marine environment; excretory system a single cell; setae on head behind lip region; male with elaborate supplements; esophageal glands open into esophageal lumen anterior to nerve ring, 3 open into stoma Super-order:


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b Soil and (rarely) freshwater environment; no excretory cell, have hypodermal glands which may be excretory (except Trichodorus); no head setae; male with delicate supplements; esophageal glands open posterior to nerve ring, opening difficult to see Super-order:


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4 a Female with 1 ovary; prominent circular amphids Monhysterida  
b Single-spiral or multiple-spiral amphids Chromadorida  
c Shepherd's crook-shaped amphid Araeolaimida  
d Somatic setae and ornamentation on body Desmodorida  
e Somatic setae, ornamentation, and head cap Desmoscolecida  
5 a Marine and brackish water Enoplida  
6 a Long and slender, soil inhabitants Isolaimiida  
b Strong, cuticularized stoma, predators Mononchida  
c Movable hollow spear Dorylaimida  
d Movable tooth  Triplonchida  
e Esophagus with multiple glands, vertebrate and invertebrate parasites Stichosomida  
7 a Three-part esophagus (corpus, isthmus and postcorpus), valve in postcorpus; corpus and postcorpus in 12 cells Sub-class:


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b Wine bottle esophagus; large nematodes (many >2.5 cm); all animal parasites Sub-class:


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c Three-part esophagus with valve in metacorpus (median bulb) and postcorpus glandular Sub-class:


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8 a Male with rays in delicate caudal alae Rhabditida  
b Male with prominent rays in lobed caudal alae Strongylida  
9 a Large stoma; most are minor parasites of birds and fish (generally < 2 cm long, except Ascaris) Ascaridida  
b Collapsed stoma; large nematodes; all use invertebrate for one host Spirurida  
c Parasites of terrestrial and aquatic vertebrates with copepods as obligatory secondary hosts Camallanida  
d Parasites of annelids and molluscs Drilonematida  
10 a Very muscular metacorpus; structured glandular postcorpus; movable tooth in stoma; individuals may connect with others at tail tip in water to form a ball of nematodes Diplogastrida  
b Stoma with buccal stylet Tylenchida go to 11
11 a Dorsal esophageal gland opening (DEGO) in metacorpus; male with rose-thorn spicule and 6 rays in caudal alae Sub-order:


b Dorsal esophageal gland opening (DEGO) in procorpus; male with blade-shaped spicule and 0 or 1 ray in caudal alae Sub-order:



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