Diplopeltidae Filipjev, 1918

Holovachov, Oleksandr, 2017, Belgopeltula belgica (Vincx & Gourbault, 1992) gen. et comb. nov. and Mudwigglus micramphidium sp. nov. from the west coast of Sweden, and reappraisal of the genus Pseudaraeolaimus Chitwood, 1951 (Nematoda: Araeolaimida: Diplopeltidae), European Journal of Taxonomy 383 (383), pp. 1-21 : 16-19

Family Diplopeltidae Filipjev, 1918

Diagnosis (emended after Fonseca & Bezerra 2014)

Cuticle visually smooth, finely striated or coarsely annulated.Lateral alae absent.Somatic sensilla present. Inner and outer labial sensilla papilliform. Cephalic sensilla setiform; their bases located at the base of the labial region, anterior to amphidial fovea. Cervical (paramphidial) sensilla present in some genera, located at the level of the amphid and posterior to it. Deirid absent. Ocelli present or absent. Amphidial fovea unispiral or loop-shaped. Secretory-excretory system present. Oral opening apical or shifted either to dorsal or ventral body side. Buccal cavity tubular, cylindrical or undifferentiated. Teeth-like structures absent. Pharynx variable in shape; pharyngeal lumen uniform in thickness along the entire pharynx length; valves absent. Female reproductive system didelphic-amphidelphic or monodelphic-prodelphic. Ovaries outstretched or reflexed antidromously. Male reproductive system diorchic. Posterior testis is either anteriorly oriented and reflexed in the anterior section (reflexed terminal section of the germinal zone) or is posteriorly directed. Spicules symmetrical; gubernaculum present. Precloacal sensilla present in some genera. Three caudal glands present, their nuclei are incaudal. Caudal glands open separately via three pores, or together via a common spinneret.

Valid genera

Araeolaimus de Man, 1888

= Araeolaimoides de Man, 1893

= Coinonema Cobb, 1920

= Parachromagaster Allgén, 1929

Belgopeltula gen. nov.

Campylaimus Cobb, 1920

Cylindrolaimus de Man, 1880

Diplopeltis Cobb in Stiles & Hassal, 1905

= Dipeltis Cobb, 1891

= Discophora Villot, 1875

Diplopeltula Gerlach, 1950

Edalonema Andrássy, 2007

= Adelonema Holovachov & Sturhan, 2003

Intasia Tchesunov & Miljutina, 2008

Metaraeolaimoides De Coninck, 1936

Morlaxia Vincx & Gourbault, 1988

Mudwigglus Leduc, 2013

Pararaeolaimus Timm, 1961

Pseudaraeolaimus Chitwood, 1951

Southerniella Allgén, 1932

Key to genera of Diplopeltidae

See Table 4 for additional diagnostic characters.

1. Amphidial fovea a transverse slit; cuticle with ten longitudinal ridges .... Edalonema Andrássy, 2007

– Amphidial fovea double-loop-shaped in male, unispiral in female .................. Belgopeltula gen. nov.

– Amphidial fovea unispiral ................................................................................................................ 2

– Amphidial fovea loop-shaped ........................................................................................................... 4

2. Basal bulb absent; freshwater or terrestrial ........................................ Cylindrolaimus de Man, 1880

– Basal bulb present; marine ................................................................................................................ 3

3. Single anterior ovary ................................................................ Intasia Tchesunov & Miljutina, 2008

– Two ovaries (anterior and posterior) ....................................................... Southerniella Allgén, 1932

4. Oral opening shifted to the ventral body side ............................ Morlaxia Vincx & Gourbault, 1988

– Oral opening apical or shifted to the dorsal body side ..................................................................... 5

5. Basal pharyngeal bulb present; ovaries antidromously reflexed ............... Mudwigglus Leduc, 2013

– Basal pharyngeal bulb absent; ovaries outstretched ......................................................................... 6

6. Lateral alae present, in some species fused with the ventral limb of the amphid ............................... ................................................................................................................... Campylaimus Cobb, 1920

– Lateral alae absent ............................................................................................................................ 7

7. Amphid in a shape of rounded loop .................................................................................................. 8

– Amphid in a shape of elongated loop ............................................................................................. 10

8. Anterior body region abruptly narrowing; amphid at a distance equal to more than five labial region diameters from the anterior end ............................................. Metaraeolaimoides De Coninck, 1936

– Anterior body region cylindrical or subcylindrical; amphid at a distance equal to less than two labial region diameters from the anterior end ............................................................................................. 9

9. Buccal cavity cup-shaped; pronounced sexual dimorphism in the amphid size (large in males and small in females) .................................................................................. Pararaeolaimus Timm, 1961 – Buccal cavity conical; no sexual dimorphism in the amphid size .......... Araeolaimus de Man, 1888

10. Cervical (paramphideal) setae absent; caudal glands open via three separate pores .......................... ................................................................................................................. Diplopeltula Gerlach, 1950

– Cervical (paramphideal) setae present; caudal glands open via common spinneret ........................11

11. Amphid located on a well-developed refractive subcuticular plate .................................................... .......................................................................................... Diplopeltis Cobb in Stiles & Hassal, 1905

– Refractive subcuticular plate absent .......................................... Pseudaraeolaimus Chitwood, 1951

Tables

Table 4. Selected diagnostic characters of genera of the family Diplopeltidae Filipjev, 1918 based on literature data supplemented with recent observations (modified after Tchesunov & Miljutina 2008).

	Araeolaimus	Belgopeltula gen. nov.	Cylindrolaimus	Campylaimus	Diplopeltis	Diplopeltula	Edalonema
Cuticular ornamentation	absent	absent	absent	longitudinal striae present or absent	absent	longitudinal striae present or absent	ten longitudinal ridges
Oral opening	apical	subdorsal	apical	subdorsal	apical	apical or subdorsal	apical
Amphideal fovea shape	rounded loop	double loop in male, unispiral in female	unispiral	elongated loop	elongated loop	elongated loop	transverse slit
Subcuticular plate supporting amphid	absent	absent	absent	absent	present	present or absent	absent
Ocelli	present	absent	absent	absent	present	absent	absent
Cervical setae	present	absent	absent	absent	present	absent	absent
Buccal cavity	conical	minute	tubular	minute	minute	cylindrical	tubular
Pharynx	with swelling at anterior ⅓	with fusiform corpus and narrow postcorpus	cylindrical	cylindrical	cylindrical	cylindrical	cylindrical
Female gonad	didelphic	didelphic	didelphic or monodelphic-prodelphic	didelphic	didelphic	didelphic	monodelphic-prodelphic
Ovaries	outstretched	reflexed	outstretched	outstretched	outstretched	outstretched	outstretched
Caudal glands open via	spinneret	spinneret	spinneret	spinneret	spinneret	three pores	caudal glands absent
	Intasia	Metaraeolaimoides	Morlaxia	Mudwigglus	Pararaeolaimus	Pseudaraeolaimus	Southerniella
Cuticular ornamentation	absent	absent	absent	absent	absent	absent	absent
Oral opening	apical	apical	subventral	apical	apical or subdorsal	apical	apical
Amphideal fovea shape	unispiral	rounded loop	rounded loop	elongated loop	rounded loop	elongated loop	unispiral
Subcuticular plate supporting amphid	absent	absent	absent	absent	absent	absent	absent
Ocelli	absent	present	absent	absent	absent	present or absent	absent
Cervical setae	absent	present	absent	absent	absent	present	absent
Buccal cavity	tubular	minute	minute	barrel-shape	cup-shaped	minute	tubular
Pharynx	with basal bulb	subcylindrical	with basal bulb	with basal bulb	cylindrical	glandular posteriorly	with basal bulb
Female gonad	monodelphic-prodelphic	didelphic	monodelphic-prodelphic	didelphic	didelphic	didelphic	didelphic
Ovaries	outstretched	outstretched	outstretched	reflexed	outstretched	outstretched	outstretched
Caudal glands open via	spinneret	?	spinneret	three pores or spinneret	three pores	spinneret	spinneret