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Illustrated Key to the Genera of Free-living Marine Nematodes in the Superfamily Chromadoroidea - Exclusive of the Chromadoridae

Introduction - Use of the Key - Taxa Included in the Key - Abbreviations Used in the Key - Key to the Genera - Alphabetical List of Genera and Illustration Sources - Acknowledgments - Selected References - References for Illustration

Introduction (Back to Top)

This is an illustrated key to 55 genera of free-living marine nematodes of the superfamily Chromadoroidea, exclusive of the Chromadoridae, (Nematoda: Chromadorida: Chromadorina). Illustrations are almost all limited to the heads and caudal regions of the included genera. Specific anatomical features are designated to facilitate use of the key.

This is the fourth in a series of keys by the authors to the groups of the free-living marine nematodes. The purpose of these keys is to provide students and other interested persons with a tool to begin the identification of free-living marine nematodes. These keys, along with those provided by Tarjan (1980) and Platt and Warwick (1983), should provide a basis for the identification of the genera of free-living marine nematodes.

Hope and Murphy (1972), Gerlach and Riemann (1974), Andrassy (1976), Lorenzen (1981), and Inglis (1983) have published classifications of free-living marine nematodes. Platt and Warwick (1988) provided descriptions and figures for the species of chromadorids reported from Britain.

The key presented herein is not intended to reflect phylogenetic relationships. It includes 55 genera of free-living marine nematodes in the suborder Chromadorina, superfamily Chromadoroidea, exclusive of the family Chromadoridae.

Although the key follows the classification of Lorenzen (1981), Jensen (1979) and Platt (1982) should be consulted regarding the Comesomatidae and Ethmolaimidae. Jensen (1979) revised the Comesomatidae and provided keys to the subfamilies, genera, and species. Lorenzen (1981) recognized the family Neotonchidae. Platt (1982) revised the family Ethmolaimidae and included the neotonchids in the Ethmolaimidae as the subfamily Neotonchinae Wieser & Hopper, 1966. Platt (1982) provided keys to the subfamilies, genera, and species of the Ethmolaimidae. Platt and Warwick (1988) also included the neotonchids in the Ethmolaimidae but did not segregate taxa at the subfamily level.

Use of the Key (Back to Top)

Couplet numbers and lower case letters refer to the location of related lower-ranked taxa. When one arrives at a family or subfamily name, rather than another couplet, the genera within that taxon immediately follow in couplets designated by lower-case letters. The parenthetical part of each couplet designation indicates the referent couplet, allowing one to work backward, as well as forward, through the key.

Illustrations in the key were obtained from published references. In some cases, portions of the anatomy shown on the drawings are labeled or emphasized with ink; in other cases pertinent anatomical details have been deleted to better portray the structures of interest. Credit is given for each illustration used.

taxa included in the key

Abbreviations Used in the Key (Back to Top)

a amphid m mandible
bc buccal cavity ps precloacal supplement
cs cephalic sensilla r rugae
eb esophageal bulb rs cervical sensilla
g gubernaculum s spicule
ga gubernacular apophysis sp small spines
lp longitudinal punctations ss somatic sensilla
ls labial sensilla t teeth

Key to the Genera (exclusive of the Chromadoridae) (Back to Top)

Chromadoroidea. Cuticle with punctations; transverse striations present or absent. Head without helmet. Amphid variable in shape, difficult to discern in some species. Only those species with a spiral or circular amphid included in the key.

[Note: When two consecutive numbers are shown, they
refer to the anterior and posterior ends of the nematode.]

1. Amphid a distinct spiral (Figs. 53a, 81a) . . . . . 2
1'. Amphid not a distinct spiral . . . . . Chromadoridae (not included)

2 (1). Anterior part of buccal cavity with 12 rugae (Fig. 13r); females with reflexed ovaries . . . . . 5
2'. Anterior part of buccal cavity without 12 rugae; females with outstretched ovaries . . . . . Comesomatidae . . . . . 3

3 (2). Posterior part of buccal cavity weakly cuticularized ; spicules short (2 anal body diameters or less) (Fig. 6s); gubernaculum with dorso-caudally directed apophyses (Fig. 4ga) . . . . . Sabatieriinae

3'. Posterior part of buccal cavity heavily or moderately cuticularized; spicules elongate (more than 2.0 anal diameters long) (Fig. 18s); gubernacular apophyses directed caudally, parallel to spicules (Fig. 18ga), or absent . . . . . 4

4 (3). Posterior part of buccal cavity collapsed, weakly cuticularized (Fig. 19bc); teeth present or absent . . . . . Comesomatinae

4'. Posterior part of buccal cavity expanded, heavily cuticularized (Fig. 42bc), teeth present or absent . . . . . Dorylaimopsinae

5 (2). Amphid unispiral (Fig. 28a); buccal cavity elongate, not funnel-shaped (Fig. 108bc) . . . . . Ethmolaimidae

5'. Amphid multispiral; buccal cavity elongate, sometimes funnel-shaped . . . . . 6

6 (5). Teeth mostly absent, mandibles present (Fig. 106m) or absent; if both teeth and mandibles absent, then cuticle with numerous longitudinal rows of small spines (Fig. 96sp) . . . . . Selachinematidae

6'. Teeth, if present, appear as a single dorsal tooth and two subventral teeth (Fig. 71t) or a single dorsal tooth (Fig. 36t). If teeth absent then buccal cavity not divided into cup-shaped and cylindrical parts; mandibles absent . . . . . 7

7 (6). Esophagus with posterior bulb; spicules typically bent about 2/3 distance from proximal end (Fig. 70s); male precloacal supplements well developed, cup-shaped . . . . . Neotonchidae

7'. Esophagus with or without a posterior bulb; spicules not characteristically bent about 2/3 distance from proximal end; precloacal supplements cup-shaped, tubular or absent . . . . . Cyatholaimidae . . . . . 8

8 (7). Ten longitudinal alae present; cuticular punctations absent (Figs. 112, 113) . . . . . Xenocyatholaimus Gerlach, 1953
8'. Longitudinal alae absent; cuticular punctations present . . . . . 9

9 (8). Precloacal supplements present in male . . . . . 10
9'. Precloacal supplements absent in male . . . . . Cyatholaiminae (in part)

10 (9). Male precloacal supplements weakly cuticularized, simple cup-shaped (Fig. 6ps) or narrow tubes; lateral differentiation present . . . . . Cyatholaiminae (in part)

10'. Male precloacal supplements strongly cuticularized, complex cup-shaped (Fig. 64ps), tubular (Fig. 2ps) or setose; lateral differentiation present or absent . . . . . 11

11 (10). Male precloacal supplements protrusible tubes (Fig. 2ps) or setose (Fig. 80ps) . . . . . Paracanthonchinae

11'. Male precloacal supplements complex, consisting of a number of elements (Fig. 64ps) . . . . . Pomponematinae

Alphabetical List of Genera and Illustration Sources (Back to Top)

Figure No. Genus Illustration Source
1-2 Aconthonchus Wieser 1955, p. 66, Figs. a, b
3-4 Actarjania Hopper 1967, p. 141, Figs. 5, 7
5-6 Biarmifer Wieser 1954, p. 11, Figs. c, e
7-8 Cervonema Gourbault 1980, p. 739, Figs. 1c, d
9-10 Cheironchus Gerlach 1964a, p. 46, Figs. a, b
11-12 Choanolaimus Riemann 1966, p. 133, Figs. 34a, c
13-14 Choniolaimus Riemann 1966, p. 110, Figs. b, d
15-16 Cobbionema Furstenberg & Heyns 1987, p. 81, Figs. 1, 4
17-18 Comesoma Wieser 1954a, p. 137, Figs. 177b, d
19-20 Comesomoides Gourbault 1980, p. 747, Figs. 4a, c
21-22 Cyatholaimus Wieser 1959, Pl. XV, Fig. 37a; Pl. XVI, Fig. 37b
23-25 Demonema Gerlach 1958, Taf. 40, Figs. 1b, c, d
26-27 Dorylaimopsis Schuurmans Stekhoven 1950, p. 147, Figs. 88A, I
28-29 Ethmolaimus Jensen 1979, p. 165, Figs. 57, 58
30-31 Filitonchoides Jensen 1986, p. 253, Figs. 6B, E
32-33 Filitonchus Platt 1982, p. 248, Figs. 36b, d
34 Gomphionchus Wieser & Hopper 1966, p. 527, Figs. 20, 21
35 Gomphionchus Platt 1982, p. 217, Figs. 14a, b
36-37 Gomphionema Wieser & Hopper 1966, p. 530, Figs. 31, 32
38-39 Gammanema Murphy 1964, p. 195, Fig. 3a; p. 196, Fig. 4
40-41 Halichoanolaimus Wieser & Hopper 1967, p. 324, Figs. 34A, 35B
42-43 Hopperia Vitiello 1969, p. 486, Fig. 1b; p. 488, Fig. 2a
44-45 Kosswigonema Gerlach 1964a, p. 45, Figs. 15a, e
46-48 Kraspedonema Gerlach 1954, p. 100, Figs. 2b, c, d
49-50 Laimella Hopper 1967, p. 144, Figs. 2, 3
51-52 Latronema Wieser 1954, p. 31, Figs. 109a, d
53-54 Longicyatholaimus Vitiello 1970, p. 476, Figs. 18A, D
55-56 Marilynia Hopper 1972, p. 75, Figs. 14, 15
57-58 Metacomesoma Wieser 1954, p. 137, Figs. 176a, c
59-60 Metacyatholaimus Gerlach 1964b, p. 73, Figs. 2b, d
61-62 Metasabatieria Timm 1961, p. 51, Figs. 35a, b
63-64 Minolaimus Vitiello 1970, p. 486, Figs. 25b, f
65-66 Nannolaimoides Ott 1972, p. 464, Figs. 4, 7
67-68 Nannolaimus Platt 1982, p. 242, Figs. 32b, d
69-70 Neotonchoides Platt 1982, p. 238, Fig. 29c
71-72 Neotonchus Platt 1982, p. 220, Figs. 16a, b
73 Paracanthonchus Wieser & Hopper 1967, p. 323, Fig. 31a
74 Paracanthonchus Inglis 1970, p. 7, Fig. 13
75-76 Paracanthonchus Wieser & Hopper 1967, p. 323, Figs. 31b, c
77-78 Paracomesoma Jensen & Gerlach, 1977, p. 61, Figs. 1a, c
79-80 Paracyatholaimus Wieser & Hopper 1967, p. 323, Figs. 32a, b
81-82 Paracyatholaimoides Boucher 1976, p. 48, Figs. 7c, f
83-84 Paralongicyatholaimus Warwick 1971, p. 101, Figs. 3a, d
85-86 Paramesonchium Jensen 1976, p. 245, Figs. 30, 36
87-88 Phyllolaimus Murphy 1963, p. 76, Figs. 2A, C
89-90 Pierrichia Vitiello 1970, p. 455, Figs. 3A, D
91-92 Pomponema Wieser & Hopper 1967, p. 321, Figs. 28a, c
93-95 Praecanthonchus Pastor de Ward 1979, p. 35, Figs. 5b,g, e
96-97 Richtersia Soetaert & Vincx 1986, p. 129, Fig. 3b
98-99 Sabatieria Wieser & Hopper 1967, p. 335, Figs. 59a, c
100-101 Scholpaniella Sergeeva 1972, p. 1293, Figs. 5, 6
102-103 Setosabatieria Platt 1985, p. 43, Fig. 9
104-105 Synonchiella Riemann 1966, p. 135, Figs. 36a, d
106-107 Synonchium Gerlach 1953, p. 556, Figs. 18a, c
108-109 Trichethmolaimus Gerlach 1956, Taf. 31, Figs. a, b
110-111 Vasostoma Wieser 1954a, p. 137, Figs. 175a, b
112-113 Xenocyatholaimus Gerlach 1953, p. 74, Figs. 1a, c
114-115 Zyzzors Inglis 1963, p. 545, Fig. 25
Wieser & Hopper 1967, p. 322, Fig. 29

Acknowledgments (Back to Top)

We express our sincere appreciation to Drs. K. B. Nguyen, R. P. Esser, and especially G. C. Smart, Jr., for their review of this manuscript and suggestions for its improvement.

Selected References (Back to Top)

References for Illustrations (Back to Top)