Nematoda
Creators: name: Hodda, Mike
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Nematoda

description: Key to morphology of individuals of different trophic groups
Number in parentheses beside couplet number refers to the couplet preceding it in the key.
1 Nematode located on or within vertebrate body or gut........................................ Parasite-Vertebrate
Nematode not located on or within vertebrate body or gut..................................................... 2
2(1) Nematode located on or within arthropod.................................................................. 3
Nematode not associated with arthropod................................................................... 6
3(2) Stylet present........................................................................................ 4
Stylet absent......................................................................................... 5
4(3) 1 to 3 large nematodes only, haemolymph clear...... Parasite-Invertebrate-Arthropod (Mermithidae or Sphaerulariidae)
Many small nematodes, haemolymph clear or cloudy.... Parasite-Invertebrate-Arthropod (Aphelenchidae or Tylenchidae)
5(3) Host haemolymph cloudy......................... Parasite-Invertebrate-Arthropod (Heterorhabditis or Steinernema).................................................................. Microbial Feeder-Processor-Particulate
Host haemolymph clear............ Parasite-Invertebrate-Arthropod (genus other than Heterorhabditis or Steinernema).................................................................... Parasite-Vertebrate (intermediate host)
6(2) Nematode located on or within invertebrate other than arthropod......................... Parasite-Invertebrate-Other
Nematode not located on invertebrate..................................................................... 7
7(6) Nematode located on or within plant or plant part............................................................ 8
Nematode not located on or within plant or plant part........................................................ 31
8(7) Nematode located on or within aerial part of plant (stem, leaves or seeds)......................................... 9
Nematode located on or within below-ground part of plants (roots, stolons, corms, tubers or bulbs)................... 19
9(8) Nematode located within plant seeds..................................... Parasite-Plant-Aerial-Internal modifier
Nematode not located within plant seeds.................................................................. 10
10(9) Nematode located in flower or fruit bud.................................. Parasite-Plant-Aerial-Internal modifier
Nematode not located in flower or fruit bud............................................................... 11
11(10) Nematode located within leaves or stem.................................................................. 12
Nematode not located within leaves or stem........................................ Parasite-Plant-Wood or bark
12(11) Nematode located on or within plant leaves................................................................ 13
Nematode located on or within plant stem................................................................. 15
13(12) Nematode located on surface of leaf............................... Parasite-Invertebrate-Arthropod (Mermithidae)
Nematode within leaf................................................................................. 14
14(13) Leaf not galled, may be distorted............. Parasite-Plant-Aerial-Internal migrator (Aphelenchoides or Ditylenchus)
Leaf galled............................... Parasite-Plant-Aerial-Internal modifier (Fergusobia and related genera)........................................................................ Parasite-Invertebrate-Arthropod
15(11) Plant live........................................................................................... 16
Plant dead................................................................... Parasite-Plant-Wood or bark
16(15) Nematode within plant stem............................................................................ 17
Nematode on surface of plant stem...................................................................... 18
17(16) Stem not woody (herbaceous).......................................... Parasite-Plant-Internal migrator-Aerial
Stem woody.................................................. Parasite-Plant-Wood or bark (Bursaphelenchus)
18(16) Stem surface smooth.................................................. Parasite-Plant-Internal migrator-Aerial
Stem surface with fibrous bark................................................... Parasite-Plant-Wood or bark
19(8) Stylet.............................................................................................. 20
No stylet (may be associated with decaying plant material or microbial decomposers).............................. 30
20(19) All or a substantial portion of nematode body within root..................................................... 21
Most of nematode body on surface of root................................................................. 27
21(20) Root modified to swelling....................................... Parasite-Plant-Internal modifier-Below ground
Root not swelled..................................................................................... 22
22(21) Nematode body swollen................................................................................................................. Parasite-Plant-Internal modifier-Below ground (parasitic juvenile or adult female)
Nematode body not swollen............................................................................ 23
23(22) Nematode adult female with vulva and/or eggs....................... Parasite-Plant-Internal migrator-Below ground
Nematode not adult female, no vulva or eggs.............................................................. 24
24(23) Stylet thick, with large terminal knobs.............................. Parasite-Plant-Internal migrator-Below ground
Stylet slender, with small terminal knobs.................................................................. 25
25(24) Juvenile nematode............................................. Parasite-Plant-Internal modifier-Below ground
Adult male nematode................................................................................. 26
26(25) Stylet and oesophagus not vestigial................................ Parasite-Plant-Internal modifier-Below ground
Stylet and oesophagus vestigial................................... Parasite-Plant-Internal modifier-Below ground............................................................Parasite-Plant-Internal migrator-Below ground
27(19) Stylet length <20µm long, with terminal knobs <5µm across................................................. 28
Stylet length> 20µm long, with terminal knobs>5µm across................................................. 29
28(27) Stylet thick, robust,>10µm or 1 head diameter long, knobs medium (3 to 5 µm across).............................................................................................. Parasite-Plant-External root feeder-Surface
Stylet thin, delicate, <15µm or 1.5 head diameters long, knobs small (<4µm across), stylet delicate............................................................................................. Parasite-Plant-External browser
29(27) Stylet anterior portion solid, evenly curved, posterior portion with small terminal flange............................................................................................. Parasite-Plant-External root feeder-Surface
Stylet anterior portion hollow, straight or curved unevenly, posterior portion with no terminal flange, large flanges or knobs............................................................. Parasite-Plant-External root feeder-Sub-surface
30(19) Mouth cavity with teeth or denticles, 1 or 2 plates in each wall................. Microbial feeder-processor-particulate
Mouth cavity without teeth, but with multiple plates in the walls............................ Microbial feeder-crusher
31(7) Mouth present or absent, mouth cavity absent, oesophagus not muscular, modified to food storage cells, intestine disconnected from oesophagus, anus absent........................................................ Parasite-Host Unknown ........................................................................ Parasite-Invertebrate-Arthropod ............................................................................ Parasite-Invertebrate-Other
Mouth present, cavity present or absent, oesophagus at least partially muscular, not modified to food storage cells, intestine connected to oesophagus, anus present................................................................... 32
32(31) Stylet present....................................................................................... 33
Stylet absent........................................................................................ 62
33(32) Stylet without terminal flanges or knobs.................................................................. 34
Stylet with terminal expansion in the form of a flange or flanges, or knobs....................................... 42
34(33) Stylet broad, diameter>30% length, aperture>30% length, body large (>1000µm long)................ Predator-Piercer
Stylet narrower, diameter <30% length, aperture <30% length................................................ 35
35(34) Lips curled forward...................................................................... Predator-Piercer
Lips not curled...................................................................................... 36
36(35) Cephalic framework large and consisting of heavily cuticularized pieces............................. Predator-Piercer
Cephalic framework absent or small and lightly cuticularized................................................. 37
37(36) Stylet long (more than 40µm long), narrow (diameter <10% length)............................................ 38
Stylet short, aspect ratio wider.......................................................................... 39
38(37) Anterior stylet solid.................................... Parasite-Plant-External root feeder-Surface (Trichoridae)
Anterior stylet hollow............................ Parasite-Plant-External root feeder-Sub-surface (Xiphinematidae)
39(37) Oesophageal bulb posterior to nerve ring.................................................................. 40
Oesophageal bulb anterior to nerve ring.................................................................. 41
40(39) Terminal oesophageal bulb short (length <2x body diameter)............ Parasite-Plant-External browser (Leptonchidae)
Terminal oesophageal bulb long (length>2x body diameter).............. Microbial feeder-Piercer (Other Dorylaimida)
41(39) Stylet lumen broad............................................................ Predator-Piercer (Seinuridae)
Stylet lumen narrow, short....................................... Parasite-Plant-External browser (Aphelenchida)............................................................................... Microbial Feeder-Piercer
42(33) Body swollen.................................... Parasite-Plant-Internal modifier-Below ground (Heteroderidae)
Body vermiform..................................................................................... 43
43(42) Stylet>25µm long................................................................................... 44
Stylet <25µm long................................................................................... 45
44(43) Anterior stylet solid.................................... Parasite-Plant-External root feeder-Surface (Trichoridae)
Anterior stylet hollow.................. Parasite-Plant-External root feeder-Sub-surface (Xiphinematidae, Tylenchida)
45(43) Stylet>20µm long................................................................................... 46
Stylet <20µm long................................................................................... 50
46(45) Head low..................................................... Parasite-Plant-Internal modifier-Below ground
Head high................................................... Parasite-Plant-External root feeder-Sub-surface
47(45) Nerve ring posterior to oesophageal bulb............................................... Microbial feeder-Piercer ........................................................................ Parasite-Plant-External browser
Nerve ring anterior to oesophageal bulb.................................................................. 48
48(47) Median oesophageal bulb absent..................................................... Microbial feeder-Piercer ........................................................................ Parasite-Plant-External browser
Median oesophageal bulb present....................................................................... 49
49(48) Cephalic framework strong, terminal knobs large (>5µm across)......... Parasite-Plant-Internal migrator-Below ground
Cephalic framework weak or absent, terminal knobs small (<5µm across).................................................................................................... Parasite-Plant-External root feeder-Sub-surface
50(45) Stylet <10µm long......................................................... Parasite-Plant-External browser
Stylet>10µm long................................................................................... 51
51(50) Juvenile............................................................................................ 52
Adult male......................................................................................... 54
Adult female........................................................................................ 62
52(51) Tail with long hyaline tip, rounded tip.............................. Parasite-Plant-Internal modifier-Below ground
Hyaline tail tip short or absent, shape variable.............................................................. 53
53(52) Tail long, filiform.......................................................... Parasite-Plant-External browser
Tail shorter, not filiform............................................ Parasite-Plant-External root feeder-Surface ........................................................................ Parasite-Plant-External browser ............................................................................... Microbial feeder-Piercer
54(51) Stylet vestigial, oesophagus poorly defined, thin............................................................ 55
Stylet not vestigial, oesophagus with defined structure, thick in places.......................................... 58
55(54) Spicules terminal, tail rounded.................................... Parasite-Plant-Internal modifier-Below ground
Spicules not terminal, tail conoid........................................................................ 56
56(55) Body thick (length <20 times maximum diameter)................... Parasite-Plant-External root feeder-Sub-surface
Body normal shape (>20 times maximum diameter)......................................................... 57
57(56) Head bulbous, with distinct constriction, high........................ Parasite-Plant-Internal migrator-Below ground
Head not bulbous (tapering, without distinct constriction (not distinctly offset) high or low....................................................................................... Parasite-Plant-External root feeder-Sub-surface
58(54) Stylet knobs large (>5µm across), strong cephalic framework............................................................................................................... Parasite-Plant-Internal migrator-Below ground
Stylet knobs small (<5µm across), light cephalic framework.................................................. 59
59(58) Tail very long, filiform...................................................... Parasite-Plant-External browser ............................................................... Parasite-Plant-External root feeder-Surface
Tail shorter, not filiform............................................................................... 60
60(59) Tail short, spicules very near end.................................. Parasite-Plant-Internal modifier-Below ground
Tail longer, spicules at side............................................................................. 61
61(60) Nerve ring around intestine, oesophageal bulb occupies>60% of body diameter............... Microbial feeder-Piercer .................................................................. Parasite-Plant-Internal migrator-Aerial ........................................................................ Parasite-Plant-External browser
Nerve ring around oesophagus.......................................................................... 62
62(61) Muscular oesophageal bulb length>2.5 times diameter................................... Microbial feeder-Piercer ............................................................... Parasite-Plant-External root feeder-Surface ........................................................................ Parasite-Plant-External browser
Muscular oesophageal bulb length <2.5 times diameter................................... Microbial feeder-Piercer ............................................................ Parasite-Plant-Internal modifier-Below ground .................................................................. Parasite-Plant-Internal migrator-Aerial ............................................................ Parasite-Plant-Internal migrator-Below ground ............................................................... Parasite-Plant-External root feeder-Surface ........................................................................ Parasite-Plant-External browser
63(51) One oesophageal bulb................................................................................. 64
Two oesophageal bulbs or swellings..................................................................... 65
64(63) Nerve ring posterior to oesophagus, oesophageal bulb occupies most of body diameter....................................................................................................... Parasite-Plant-External browser ............................................................................... Microbial feeder-Piercer
Nerve ring anterior to intestine, stylet moderate or short............................ Parasite-Plant-External browser
65(63) Stylet knobs large (>5µm across), strong cephalic framework........... Parasite-Plant-Internal migrator-Below ground
Stylet knobs small (<5µm across), light cephalic framework.................................................. 66
66(65) Tail very long, filiform...................................................... Parasite-Plant-External browser
Tail shorter, not filiform............................................ Parasite-Plant-External root feeder-surface ........................................................................ Parasite-Plant-External browser ............................................................................... Microbial feeder-Piercer
67(31) Mouth cavity tiny or absent, oesophagus not muscular, not connected to gut and modified as food storage cells.............................................................................................. Parasite-Invertebrate
Mouth cavity connected to oesophagus and intestine........................................................ 68
68(67) Mouth cavity blocked or filled........................................... Microbial feeder-Processor-Particulate .................................................................................. Parasite-Invertebrate
Mouth cavity not blocked or filled....................................................................... 69
69(68) Mouth narrow (<20% head diameter).................................................................... 70
Mouth broad (>20% head diameter)...................................................................... 73
70(69) Stoma with no teeth (within mouth cavity or not)........................................................... 71
Stoma with teeth (within mouth cavity or not)............................... Microbial feeder-Processor-suspension
71(70) Mouth with more than 2 separate thickened plates in wall................................ Microbial feeder-Crusher
Mouth with 2 or less thickened plates in wall.............................................................. 72
72(71) Mouth with longitudinal ridges around opening (cheilorhabdions elaborated into longitudinal ridges)....................................................................................... Microbial feeder-Processor-suspension
Mouth without longitudinal ridges around opening ridges simple (cheilorhabdions not elaborated)........................................................................................... Microbial feeder-Sucker-suspension
73(69) Stoma with no teeth (within mouth cavity or not)........................................................... 74
Stoma with teeth (within mouth cavity or not).............................................................. 77
74(73) Mouth with more than 2 separate thickened plates in wall................................ Microbial feeder-Crusher
Mouth with 2 or less thickened plates in wall.............................................................. 75
75(74) Mouth with longitudinal ridges around opening (cheilorhabdions elaborated into longitudinal ridges), mouth cavity <50% diameter deep........................................................ Microbial feeder-Processor-suspension
Mouth without longitudinal ridges around opening ridges simple (cheilorhabdions not elaborated), mouth cavity>50% diameter deep............................................................................................... 76
76(75) Mouth containing denticles............................................. Microbial feeder-Processor-Particulate
Mouth not containing denticles............................................ Microbial feeder-Sucker-Particulate
77(73) Tooth near entrance to mouth....................................................... Microbial feeder-Scraper
Tooth not near entrance to mouth........................................................................ 78
78(77) Body small to medium size, mouth with mostly thin cuticular lining, diameter <50% of head diameter...................................................................................... Microbial feeder-Processor-Particulate
Body medium to large size, mouth with mostly greatly thickened cuticle, diameter>50% of head diameter Predator-Chewer
Note that many nematodes fall into more than one trophic group, and that the different types of parasites of plants are almost indistinguishable in some cases.
description: Published as part of Hodda, Mike, 2022, Phylum Nematoda: feeding habits for all valid genera using a new, universal scheme encompassing the entire phylum, with descriptions of morphological characteristics of the stoma, a key, and discussion of the evidence for trophic relationships, pp. 318-451 in Zootaxa 5114 (1) on pages 341-344, DOI: 10.11646/zootaxa.5114.1.3, http://zenodo.org/record/6391138