Phylum Nematoda                                            

Rev 08/03/2020  

Nematoda
 
Enoplea Chromadorea
Enoplia Dorylaimia Chromadoria
 
  Enoplida   Dorylaimida   Rhabditida
  Triplonchida   Mermithida   Plectida
Mononchida Araeolaimida
      Dioctophymatida   Monhysterida
      Trichinellida   Desmodorida
      Isolaimiida   Desmoscolecida
      Muspiceida   Chromadorida
      Marimermithida    

Key to the Orders and Suborders of Nematoda:

              (Compiled from Decraemer and Smol, 2011; De Ley and Blaxter 2002, 2004, 2006; Maggenti, 1981; and lectures by Maggenti, 1992)
1 a
Esophagus cylindrical or bottle-shaped; amphids usually post-labial; excretory system single-cell hypodermal glands; male usually with 2 testes; caudal alae rare; phasmids absent
Class:  Enoplea go to 2
b Esophagus often subdivided into bulbs; amphid apertures on lips, often difficult to see, or posterior to lips and obvious - round or coiled; gonads single or paired in both male and female Class:   Chromadorea go to 8  
2 a Anterior sensillae often in 3 whorls of inner labial papillae, outer labial setae and cephalic setae; metanemes (filamentous structures in lateral chors) present; caudal glands present; esophageal glands open in or near stoma Sub-class: Enoplia go to 3
b Anterior sensillae rarely setiform; stoma with teeth or odontostyle; esophagus cylindrical, bottle-shaped or a stichosome; caudal glands usually absent; esophageal glands open in posterior region of esophagus Sub-class:  Dorylaimia go to 4
3 a Spicule protractor muscles attached to proximal enlargement; metanemes present; marine and fresh water Enoplida go to 10
b Spicule protractor muscles form a pouch around spicules; protrusible tooth in some forms Triplonchida go to 11
4 a Movable hollow spear; esophagus expanded posteriorly - bottle-shaped. Dorylaimida go to 12
b Glandular esophageal stichosome and intestinal trophosome; juveniles are parasites of invertebrates. Mermithida go to 15
c Esophagus vestigial;  parasites of vertebrates in all life stages Muspiceida go to 17
d Esophagus cylindrical throughout   go to 5
5 a Juveniles are parasites of invertebrates; adults free-living Marimermithida go to 19
b All stages parasitic; adults are vertebrate parasites, juveniles with or without intermediate hosts   go to 6
c All stages free-living   go to 7
6 a Posterior esophagus a stichosome; onchiostyle present; monovarial; anphids pore-like Trichinellida go to 16
b Anterior end has a sucker; males with bell-shaped bursa Dioctophymatida go to 18
7 a Strong, large, cuticularized stoma with prominent dorsal tooth; predators of nematodes Mononchida go to 13
b Long and slender; tubular stoma without teeth; stoma without lips; soil inhabitants Isolaimiida go to 14
8 a Amphids usually pore-like, on lips; cephalic sensillae on lip region; phasmids present; caudal glands absent; mainly terrestrial, rarely freshwater or marine; include free-living, animal parasites, plant parsites Rhabditida go to 26
b Amphids post-labial, varied shapes; phasmids absent; somatic seta common; mainly free-living aquatic organisms   go to 9
9 a Anterior sensillae in three whorls, inner labial, outer labial and cephalic; amphids var from circular to complex spirals, post-labial and usually posterior to cephalic setae; stoma funnel-shaped with a dorsal tooth and two smaller subventral teeth; esophagus cylindrical with posetrior bulb; females diovarial; mainly marine Chromadorida go to 20
b Brownish cuticle; anterior sensillae in three whorls, inner labial, outer labial and cephalic; amphids spiral, posterior to cephalic setae; dorsal and smaller subventral teeth; esophagus cylindrical with enlarged end bulb Desmodorida go to 21
c Anterior sensillae in three whorls, inner labial, outer labial and cephalic, cephalic setae on peduncles; amphids large, on head; ocelli may be present; small stoma with small teeth; esophagus cylindrical; females diovarial; mainly marine Desmoscolecida go to 23
d Small, slender nematodes with a slender tail region; three whorls of anterior sensilla; amphids round; both sexes with one or two gonads;  Mainly aquatic and wet soil environments Monhysterida go to 22
e Anterior sensillae in three whorls, inner labial, outer labial and cephalic; stoma with 3 to 6 teeth on anterior edge; amphids loop-shaped; ocelli may be present; esophagus cylindrical with no posterior enlargement Araeolaimida go to 24
f Labial sensilla papilliform, cephalic sensilla usually setiform; qamphids circular or simple spiral;  esophagus cylindrical, with or without basal bulb; females usually diovarial Plectida go to 25
10 a Enoplida;  amphids pocket-shaped; esophagus cylindrical; 3 esophageal glands opening in or near stoma; excretory canal present; marine and freshwater Enoplina  
b Enoplida;  amphids pocket-shaped; stoma elongated, without teeth or with 3-5 moveable teeth; esophagus cylindrical; excretory canal present; mainly marine but also freshwater Ironina  
c Enoplida; amphids pocket-shaped; stoma large, refractive, with 3 teeth; esophagus cylindrical; excretory canal present; mainly marine but also freshwater Oncholaimina
d Enoplida; amphids spiral; stoma with 1 or more teeth; esophagus cylindrical; females diovarial; mainly marine Tripyloidina  
e Enoplida; amphids pocket-shaped; stoma with dorsal tooth; esophagus cylindrical with terminal bulb; excretory canal present; females diovarial; soil and freshwater inhabitants Campydorina  
f Enoplida; amphids pore or pocket-shaped; stoma vestigial, without teeth; esophagus slender, cylindrical, enlarged posteriorly; soil and freshwater inhabitants Alaimina
g Enoplida; amphids spiral; stoma with teeth; esophagus cylindrical; females diovarial; mainly marine, some freshwater Trefusiina  
11 a Triplonchida;  stoma with curved or complex spear; sensilla papilliform; esophagus with elongate prosterior bulb Diphtherophorina  
b Triplonchida; stoma wide and refractive or funnel-shaped; usually with teeth; spinneret at tail tip Tobrilina  
c Triplonchida;  stoma narrow with a dirsal and two small subventral teeth; well-developed caudal glands opening at terminal spinneret  Tripylina  
12 a Dorylaimida;  stoma with axial odontostyle Dorylaimina  
b Dorylaimida; stoma withgrooved subventral mural tooth Nygolaimina  
13 a Mononchida;  stoma large, wide with 1 to 3 teeth and/or rows of denticles Mononchina  
b Mononchida;  Stoma narrow with a single subventral tooth Bathyodontina  
14 a Isolaimiida; Isolaimiina  
15 a Mermithida; Mermithina  
16 a Trichinellida; Trichinellina
17 a Muscipeicida; Muscipeicina  
18 a Dioctophymatida; Dioctophymatina  
19 a Marimermithida; Marimermithina
20 a Chromadorida; Chromadorina  
21 a Desmodorida; Desmodorina  
22 a Monhysterida; Monhysterina  
b Monhysterida; Linhomoeina  
23 a Desmoscolecida; Desmoscolecina  
24 a Araeolaimida; Araeolaimina  
25 a Plectida; Plectina  
26 a Rhabditida;  stoma with a protrusible stomatostyle; lip region simple; posterior esophageal region either a bulb without valve or overlapping glands Tylenchina; Tylenchomorpha  
b Rhabditida; stoma without teeth or with denticles; lip region simple; esophageal corpus without bulb; posterior bulb with valve Tylenchina; Panagrolaimorpha  
c Rhabditida; stoma without teeth or with denticles; lip region with probolae; esophageal corpus without bulb; posterior bulb with valve Tylenchina; Cephalobomorpha  
d Rhabditida;  stoma with teeth; lip region simple; corpus with muscular metacorpus; no valve in posterior bulb Rhabditina; Diplogasteromorpha  
e Rhabditida; stoma without teeth or with denticles; lip region simple; corpus with metacorpus; posterior bulb with valve Rhabditina; Rhabditomorpha  
f Rhabditida;  juveniles with cephalic hooks; multinucleate esophageal glands; parasites of animals Spirurina  
Decraemer, W. 2011.  Systematics and molecular phylogenetics.  Part I.  General systematics.  University of Ghent, 89p.
DeLey et al., 2006
De Ley and Blaxter, 2002, 2004
Maggenti, 1981; and lectures by Maggenti, 1992

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