Paracyatholaimus Micoletzky, 1923

Tchesunov, Alexei V., 2008, Three new species of free­living nematodes from the South­East Atlantic Abyss (DIVA I Expedition) *, Zootaxa 1866, pp. 151-174 : 153-157

Paracyatholaimus Micoletzky, 1923

Wieser, 1954a: 26, emended

Diagnosis

Cuticle punctated, lateral differentiation hardly developed. Six outer labial sensilla + four cephalic sensilla setose, in a single circle. Amphidial fovea multispiral. Cheilostoma armoured with twelve rugae; distinct dorsal tooth, often supplemented with smaller subventral teeth and occasionally other denticles in the stegostoma. Precloacal ventromedian supplements as setae­like organs half inserted into the body. Gubernaculum hardly dilated at the distal end and devoid of denticles or serrations. Tail conical or with more or less slender cylindrical distal portion.

Type species

Cyatholaimus dubiosus Bütschli, 1874 .

List of valid species

1 Paracyatholaimus arcticus Kreis, 1963 . Kreis, 1963: 39 –40, fig. 20 A–C; Iceland.

2 Paracyatholaimus botosaneanui Andrássy, 1973 . Andrássy, 1973: 259 –261, Abb. 9 A–C; Cuba.

3 Paracyatholaimus chilensis Gerlach, 1953 . Gerlach, 1953b: 19 –21, Abb. 9 a–e; Chile.

4 Paracyatholaimus diva sp. nov. Present paper.

5 Paracyatholaimus dubiosus ( Bütschli, 1874) . Bütschli, 1874: 48, fig. 31 a, b (= Cyatholaimus dubiosus ); Kiel Bay. Micoletzky, 1922: 377 (to subgenus Paracyatholaimus ). Meyl, 1954: 428 –429, Abb. 2 a–f; (Mediterranean).

6 Paracyatholaimus duplicatus Gerlach, 1964 . Gerlach, 1964b: 77 –78, Abb. 5 a–d; Maldive Islands.

7 Paracyatholaimus helicellus Wieser, 1954 . Wieser, 1954a: 27, fig. 107 a–c; Chile.

8 Paracyatholaimus intermedius (de Man, 1880). De Man, 1880: 16 –17 (= Cyatholaimus intermedius ); De Man, 1884: 52 –54, fig. 25–25f (= Cyatholaimus intermedius ); Kattegat. Gerlach, 1953a: 21 –22, Abb. 5; Baltic Sea. Gerlach, 1965: 127 –128, Abb. 9 a–c; Spitzbergen. Bussau, 1990: 170 –172, Abb. 3 A–C; North Sea, coastal dunes.

9 Paracyatholaimus lewisi Coomans, Vincx & Decraemer, 1985 . Coomans et al., 1985: 268, fig. 2 A–F; Solomon Islands, freshwater pool on a coral island; no males described.

10 Paracyatholaimus occultus Gerlach, 1956 . Gerlach, 1956: 91 –92, Abb. 29 a–c; Kiel Bay.

11 Paracyatholaimus paucipapillatus Gerlach, 1955 . Gerlach, 1955: 265 –267, Abb. 7 a–e; El Salvador.

12 Paracyatholaimus pentodon Riemann, 1966 . Riemann, 1966: 125 –127, Abb. 31 a–e; North Sea. Platt & Warwick, 1988: 282, fig. 128; East and West Scotland.

13 Paracyatholaimus pesavis Wieser & Hopper, 1967: 268 –269, pl. XVI, fig. 32 a–e; Florida.

14 Paracyatholaimus proximus ( Bütschli, 1874) . Bütschli, 1874: 49, fig. 30 a–b (= Cyatholaimus proximus ); Kiel Bay. De Man, 1922: 239 –240, fig. 28 a, b (= Cyatholaimus proximus ); North Sea. Micoletzky, 1924: 140 (to subgenus Paracyatholaimus ).

15 Paracyatholaimus pugettensis Wieser & Hopper, 1967 . Wieser, 1959: 37 –38, fig. 35 a–c (= Longicyatholaimus quadriseta Wieser, 1959 , nec L. quadriseta Wieser 1954 ); Puget Sound, Washington, USA. Wieser & Hopper, 1967: 265.

16 Paracyatholaimus quadriseta (Wieser, 1954) . Wieser, 1954a: 13, fig. 98 a, b (= Longicyatholaimus quadriseta ); Chile. Hopper, 1972: 69 (= Marilynia quadriseta ).

17 Paracyatholaimus rotundus Gerlach, 1964 . Gerlach, 1964a: 25, Abb. 2 d–e; Red Sea.

18 Paracyatholaimus saradi Gerlach, 1967 . Gerlach, 1967: 30 –31, Abb. 15 a–e; Red Sea.

19 Paracyatholaimus separatus Wieser, 1954 . Wieser, 1954b: 194 –196, Abb. 12 a–c; Mediterranean.

20 Paracyatholaimus spinulosus Jensen, 1985 . Jensen, 1985: 253 –254, fig. 7 A–F; Gulf of Mexico.

21 Paracyatholaimus ternus Wieser, 1954 . Wieser, 1954a: 27 –28, fig. 108 a–e; Chile.

22 Paracyatholaimus truncatus ( Cobb, 1914) . Cobb, 1914: 60 –62, fig. 17 (= Cyatholaimus truncatus ); Florida, fresh or brackish water. Micoletzky, 1922: 377 (to subgenus Paracyatholaimus ). Finding of Riemann (1970) in a similar habitat at the Caribbean coast of Colombia may be doubtful because of the lesser male body length (1050 vs 1600 µ m), strong conical inner labial papillae, other pattern of four preanal supplementary organs (both posteriormost and penultimate organs are situated at the level of spicules while those of the type specimen are separated by much greater distances).

23 Paracyatholaimus vancouverensis Sharma & Vincx, 1982: 276 –278, fig. 15–23; British Columbia.

24 Paracyatholaimus vitraeus Gerlach, 1957 . Gerlach, 1957: 140 –141, Abb. 21 l–o; Brazil.

Remarks to species composition of the genus Paracyatholaimus

Four species originally assigned to Paracyatholaimus , i.e. choanolaimoides Stekhoven, 1942, effilatus Stekhoven, 1946, major Kreis, 1928 and tyrrhenicus Brunetti, 1949, were later transferred to other genera by various authors ( Gerlach & Riemann 1973) and are not considered here.

Twenty­seven species of Paracyatholaimus are enumerated in the NeMys ( Deprez et al. 2005) where P. parasaveljevi Allgén, 1935 is designated species inquirenda. Here four more other species are considered as species inquirendae because of insufficient type material lacking adult stages and/ or incomplete descriptions:

Cyatholaimus chungsani Hoeppli et Chu, 1932 ; China. The species was shifted to Paracyatholaimus by Meyl (1954) and, missing in the NeMys list, is here considered as species inquirenda because of the very poor original description even lacking details actually indicating its affiliation with Paracyatholaimus . This is one of three species ascribed to Paracyatholaimus which were found in fresh­water habitats.

Paracyatholaimus exilis (Cobb, 1898) Micoletzky, 1924 (= Cyatholaimus e. Cobb, 1898); Australia. The original description is based on only a female specimen and lacks illustrations.

Paracyatholaimus oistospiculoides (Allgén, 1935) Wieser, 1954 (= Paracanthonchus o. Allgén, 1935); Norway Sea. The original description and drawings based on a single male specimen are too poor to determine the genus.

Paracyatholaimus parasaveljevi Allgén, 1935 ; Norway Sea. Wieser (1954a) qualified the species as species inquirenda.

Paracyatholaimus tenuispiculum (Allgén, 1951) Wieser, 1954 (= Paracanthonchus t. Allgén, 1951); Hawaii. The original description and drawings are based on a single male specimen and lacks many details such as amphids and length of anterior setae.

Illustrated guide for species of Paracyatholaimus ( Figs 1 & 2 , Table 1)

The guide is a set of simplified images ( Figs 1 & 2 ) constructed in some accordance with the approved practice of Platt (1984) and others (e.g., Platt & Warwick, 1998). Species of Paracyatholaimus differ from one another in rather fine morphological details concerning mainly length of anterior setae, number of turns in the multispiral amphidial fovea, supplementary organs and copulatory apparatus. The species can neither be disposed in a morphological continuum nor grouped in any evident morphological clusters. Therefore, it is not easy to develop a convenient polytomous or dichotomous key. I arrange the images of species in alphabetical order. An important component of the guide is Table 1, where the most important morphometric data are summarized.

TABLE 1. Morphometry of valid Paracyatholaimus species (males).

Species Characters

L a c o.l.s., μ m am.w., m, amphid, c’ spic., m suppl. n.

% c.b.d. number

of turns

Figures

FIGURE 1. Pictorial guide for valid species of Paracyatholaimus. Part 1, beginning. Simplified images of species come from the published descriptions: arcticus — Kreis, 1963; botosaneanui — Andrássy, 1973; chilensis — Gerlach, 1953 b; diva — orig.; dubiosus — Meyl, 1954; duplicatus — Gerlach, 1964 b; helicellus — Wieser, 1954 a; intermedius — Gerlach, 1953 a; lewisi — Coomans et al., 1985; occultus — Gerlach, 1956; paucipapillatus — Gerlach, 1955; pentodon — Riemann, 1966.

FIGURE 2. Pictorial guide for valid species of Paracyatholaimus. Part 2, ending. Simplified images of species come from the published descriptions: pesavis — Wieser & Hopper, 1967; proximus — de Man, 1922; pugettensis — Wieser, 1959; quadriseta — Wieser, 1954 a; rotundus — Gerlach, 1964 a; saradi — Gerlach, 1967; separatus — Wieser, 1954 b; spinulosus — Jensen, 1985; ternus — Wieser, 1954 a; truncatus — Cobb, 1914; vancouverensis — Sharma & Vincx, 1982; vitraeus — Gerlach, 1957.