Key to Families (and Subfamilies) of Plant and Soil Nematodes

Rev. 10/15/12

1

a

Nematodes with a protrusible stylet (stomatostyle) or spear (odontostyle)

go to 2

 

b

Nematodes without protrusible stylet or spear

go to 24

 

2

a

Stylet and three-part esophagus with median bulb (metacorpus), males with or without bursa

go to 3

 

b

Spear and two-part esophagus with posterior swollen (postcorpus), males usually without bursa but with supplements  

go to 16

 

3

a

Median bulb large with refractive valve, flattened against body wall, stylet knobs absent or small

go to 4

 

b

Median bulb not refractive, stylet knobs obvious

go to 5

 

4

a

Stylet without knobs, tail rounded, male with bursa

Aphelenchidae

 

b

Stylet with small knobs, tail pointed, male usually without bursa 

Aphelenchoididae

Key to some Genera

5

a

Esophageal glands overlap intestine

go to 6

 

b

Esophageal glands enclosed in bulb that abuts intestine

go to 11

 

6

a

Cephalic framework well-developed, lip-region high; females with two gonads

go to 7

 

b

Posterior gonad reduced to a post-uterine sac, vulva at 70-90%, lip-region flattened or cephalic framework absent 

go to 10

 

7

a

Tail tip, anus and vulva in close proximity on posterior of swollen female, male body twisted, male without bursa

go to 8

 

b

Anus and vulva anterior to tail tip even when female swollen, male body not twisted, male with bursa

go to 9

 

8

a

Juvenile and female stages are sedentary endoparasites, female greatly swollen; male without bursa, body twisted, migratory in soil

Body of dead female forms cyst and retains some or all eggs – subfam. Heteroderinae

Heteroderidae

Key to some Genera

b

Juvenile and female stages are sedentary endoparasites, female greatly swollen; male without bursa, body twisted, migratory in soil

Female body does not form cyst, eggs deposited in matrix – subfam. Meloidogyninae

c

Adult females sedentary endoparasites, greatly swollen; pre-adults vermiform; male without bursa, body twisted, migratory in soil

Female body does not form cyst, eggs deposited in matrix – subfam. Nacobboderinae

9

a

Stylet 2-3 x stylet body diameter, tail < 2 x anal body diameter, body spiral when heat-killed, vulva around 60% 

Mature female remains vermiform – subfam. Hoplolaiminae 

Hoplolaimidae

Key to some Genera

b

Stylet 2-3 x stylet body diameter, tail < 2 x anal body diameter, body spiral when heat-killed, vulva around 60% 

Mature female saccate sedentary semi-endoparasite – subfam. Rotylenchulinae

c

Tail > 2.5 x anal body diameter, phasmids on tail region 

 Long nematodes, stylet > 3 x stylet body diameter – subfam. Belonolaiminae

Dolichodoridae

Key to some Genera

d

Tail > 2.5 x anal body diameter, phasmids on tail region 

Stylet < 1.5 x stylet body diameter – subfam. Telotylenchinae

10

a

Lip-region flattened but cephalic framework well-developed 

Female remains vermiform – subfam. Pratylenchinae 

Pratylenchidae

Key to some Genera

b

Lip-region flattened but cephalic framework well-developed 

Female a saccate endoparasite – subfam. Nacobbinae

c

Cephalic-framework weak or absent

Anguinidae

Key to some Genera

11

a

Females with two gonads, males with caudal bursa 

Dolichodoridae

Key to some Genera

b

Posterior female gonad reduced to a post-uterine sac, males with adanal bursa (if present)

go to 12

 

12

a

Stylet short (< stylet body diameter), tail pointed to filiform

go to 13

 

b

Stylet long so that knobs are close to median bulb valve, procorpus swollen and fused with metacorpus

go to 14

 

13

a

Tail long and filiform (>5 x anal body diameter)

Tylenchidae

Key to some Genera

b

Tail pointed (<5 x anal body diameter), cephalic framework absent 

Anguinidae

Key to some Genera

14

a

Thick cuticle with coarse striations

go to 15

 

b

Female swollen, excretory pore posterior on body, female a saccate sedentary semi-endoparasite – subfam. Tylenchulinae

Tylenchulidae

Key to some Genera

c

Cuticle with fine striations, male often without stylet, body C-shaped – subfam. Paratylenchinae

15

a

Large body diameter, sausage shape, slow moving, anchor-shaped stylet knobs – subfam. Criconematinae  

Criconematidae

Key to some Genera

b

Extra cuticular sheath, pointed tail, rounded stylet knobs – subfam. Hemicycliophorinae

16

a

Spear with complex configuration, loose-fitting cuticle

Diphtherophoridae

 

b

Spear simple, cuticle not loose but may be swollen

go to 17

 

17

a

Spear dorsally curved, anus almost terminal

Trichodoridae

Key to some Genera

b

Spear straight, anus not terminal - tail present

go to 18

 

18

a

Long, slender nematodes (1-12 mm), spear > 50 Ám, long spear extension (odontophore)

Longidoridae

Key to some Genera

b

Short spear

go to 19

 

19

a

Postcorpus of esophagus with muscular sheath

Belondiridae

Key to genera of Belondiridae

b

No muscular sheath around esophagus

go to 20

 

20

a

Spear extension (odontophore) thick and curved 

Leptonchidae

Key to genera of Leptonchidae

b

Spear extension not curved 

go to 21

 

21

a

Plump nematodes, tail rounded, with or without point

go to 22

 

b

Slender nematodes, tail conoid to filiform

go to 23

 

22

a

Spear slightly curved, small opening

Nordiidae

Key to genera of Nordiidae

b

Spear with large opening, cuticle appears layered at tail

Aporcelaimidae

Key to genera of Aporcelaimidae

23

a

Large nematodes (>2 mm), tail filiform (may be rounded in male)

Thornenematidae

 

b

Medium size (1-2 mm), tail conoid, body generally curved

Qudsianematidae

Key to genera of Qudsianematidae

24

a

Body asymmetrical, caterpillar-like

Bunonematidae

 

b

Body symmetrical

go to 25

 

25

a

Median bulb present, tail filiform

Diplogasteridae

 

b

Median bulb absent

go to 26

 

26

a

Esophagus with terminal bulb or swelling

go to 27

 

b

Esophagus cylindrical, no swellings

go to 37

 

27

a

Terminal bulb without valves

go to 28

 

b

Terminal bulb with valves

go to 29

 

28

a

Cuticle not striated

Monhysteridae

 

b

Cuticle clearly striated 

Bastianiidae

 

29

a

Aquatic forms;  cuticle striated and punctated 

Chromadoridae

 

b

Cuticle without punctations

go to 30

 

30

a

Stoma cavity with teeth, tail filiform

Diplogasteridae

 

b

Stoma cavity without teeth

go to 31

 

31

a

Head with labial extensions or crown

go to 32

 

b

Head without extensions

go to 34

 

32

a

Head with lateral cuticular extensions

Plectidae

 

b

Head with anterior extensions only

go to 33

 

33

a

Labial extensions crown-shaped

Teratocephalidae

 

b

Labial-extensions thorn- or antler-shaped

Cephalobidae

 

34

a

Tail tip with spinneret, amphids easily visible, males with tubular supplements

Plectidae

 

b

Tail tip without spinneret

go to 35

 

35

a

Stoma cavity cylindrical, cuticular walls, males with bursa

Rhabditidae

 

b

Stoma cavity funnel-shaped, walls not cuticular, posterior female gonad reduced, anterior gonad reflexed and extending beyond vulva

go to 36

 

36

a

Stoma cavity clearly present, anteriorly cylindrical

Panagrolaimidae

 

b

Stoma cavity difficult to see, only anterior section open

Cephalobidae

 

37

a

Cuticle striated

Bastianiidae

 

b

Cuticle smooth 

go to 38

 

38

a

Slender nematodes, no obvious stoma cavity or setae

Alaimidae

 

b

Clear stoma cavity or setae

go to 39

 

39

a

Amphids round, clearly visible

Monhysteridae

 

b

Amphids difficult to see, not round

go to 40

 

40

a

Stoma cavity large, walls cuticular walls

go to 41

 

b

Stoma cavity funnel-shaped or closed anteriorly, walls not cuticular

go to 42

 

41

a

Tail filiform, setae present 

Prismatolaimidae

 

b

Tail not filiform, large stoma cavity with teeth 

Mononchidae

 

42

a

Funnel-shaped stoma with small teeth

Tobrilidae

 

b

Stoma closed anteriorly, one tooth and two tiny denticles in lumen

Tripylidae

 

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February 2011

 Howard Ferris                           Key modified from:    Tom Bongers

Department of Nematology                                         Wageningen University

University of California                                                Wageningen

Davis, CA 95616                                                        The Netherlands