Hypodontolaimus de Man, 1886

Venekey, Virag, Gheller, Paula F., Kandratavicius, Noelia, Cunha, Beatriz Pereira, Vilas-Boas, Ana Carolina, Fonseca, Gustavo & Maria, Tatiana F., 2019, The state of the art of Chromadoridae (Nematoda, Chromadorida): a historical review, diagnoses and comments about valid and dubious genera and a list of valid species, Zootaxa 4578 (1), pp. 1-67 : 38-39

Genus Hypodontolaimus de Man, 1886

The genus Hypodontolaimus was erected by de Man (1886) to accommodate Spilophora inaequalis ( Bastian, 1865) . Wieser (1954) proposed the synonimization of Iotadorus Cobb, 1920 and Ptycholaimellus with Hypodontolaimus , and divided the genus in two groups according to the length of cephalic and somatic setae and the type of the inner labial papillae. In the same study two new species were described ( H. steineri and H. dimorphus ), and the species H. minor and H. norvegicus were transferred to Chromadorita . Wieser (1954) also presented a key with 16 valid species. H. heymonsi ( Steiner, 1921) was subsequently considered species inquirendum since males were not described ( Wieser & Hopper, 1967). Later, 23 species were considered valid by Platt & Warwick (1988), including H. heymonsi , which was already considered as species inquirendum by Wieser & Hopper (1967). After Platt & Warwick (1988), five species were described in the genus ( H. kiseloevi Baranova & Dashchenko, 1992 ; H. plurisetus Baranova & Dashchenko, 1992 ; H. marleenae Muthumbi & Vincx, 1998 ; H. antarcticus Andrássy & Gibson, 2007 and H. ventrapophyses Huang & Gao, 2016 ). H. sivertseni is considered as species inquirendum due to the lack of detailed description of the cuticle (there is no mention to the longitudinal rows of larger dots which is diagnostic character of Hypodontolaimus ). We recognize 26 valid species within this genus. The recent work of Huang & Gao (2016) presents an identification key for all valid species, except H. golikovi Platonova, 1971 ; H. kiseloevi ; H. plurisetus and H. punctulatus ( Cobb, 1920) . The authors did not consider H. punctulatus a valid species stating that this species is known only from females but this is a mistake as there are males in the original description made by Cobb (1920). The other three species were left out without any explanation.

Hypodontolaimus is differentiated from Dichromadora and Ptycholaimellus by having a large muscular buccal bulb and a sclerotized dorsal apophysis at the level of the dorsal tooth ( Inglis 1969 and Muthumbi & Vincx, 1998a). Although the differences among these genera are meagre, many authors still recognize them as valid genera ( Decraemer & Smol 2006; Andrássy & Gibson 2007 and Tchesunov 2014).

Diagnosis (modified from Andrássy & Gibson 2007 and Tchesunov 2014): Cuticle with homogeneous punctations, interrupted only on the body sides with two longitudinal rows of larger dots. Six small outer labial setae or papillae and four cephalic setae in separate circles. Inner labial sensilla may be conspicuous in some species ( H. galapagensis Blome, 1985 and H. setosoides Blome, 1982 ). Somatic setae may be present. Amphideal fovea transverse slit-like. Buccal cavity with a dorsal apophyses and a very prominent S-shaped dorsal tooth; in front of the stoma there is a heavily cuticularized dorsal thickening. Small ventrosublateral teeth may be present. Peribuccal pharyngeal tissue swollen, symmetrically or asymmetrically, in the latter case surrounding the dorsal tooth; the terminal bulb single. The excretory cell conspicuous and large. Males usually with precloacal supplements. Mostly marine genus, but four species were also recovered in brackish waters [ H. angelae Inglis, 1961 , H. antarcticus , H. balticus ( Schneider, 1906) and H. inaequalis ].

Number of valid species: 26

Genus Hypodontolaimus de Man, 1886

Syn. Iotadorus Cobb, 1920

VALID SPECIES

1. Hypodontolaimus abyssalis Allgén, 1933 ( Sweden, Röberg)

2. Hypodontolaimus angelae Inglis, 1961 ( South Africa, Kleinemonde River)

3. Hypodontolaimus antarcticus Andrássy & Gibson, 2007 (East Antarctica, Vestfold Hills)

4. Hypodontolaimus balticus ( Schneider, 1906) Filipjev, 1918 (Baltic Sea)

Syn. Chromadora baltica Schneider, 1906

Hypodontolaimus buetschlii Filipjev, 1918

Hypodontolaimus striatus Ditlevsen, 1918

Spilophorella paradoxa sensu Coles, 1960

5. Hypodontolaimus colesi Inglis, 1962 ( France, Banyuls-sur-mer)

6. Hypodontolaimus dimorphus Wieser, 1954 ( Chile, Tenglo Island)

7. Hypodontolaimus galapagensis Blome, 1985 ( Ecuador, Archipelago of Galapagos)

8. Hypodontolaimus golikovi Platonova, 1971 (Sea of Japan, Bay of Possjet)

9. Hypodontolaimus inaequalis ( Bastian, 1865) de Man, 1886 ( Norway, Oslofjord)

Syn. Spiliphera inaequalis Bastian, 1865

10. Hypodontolaimus interruptus Wieser & Hopper, 1967 ( USA, Virginia Key)

11. Hypodontolaimus kiseloevi Baranova & Dashchenko, 1992 (Pacific Ocean, Coral Sea)

12. Hypodontolaimus longiseta ( Allgén, 1933) Wieser, 1954 ( Norway, port of Ilen)

Syn. Dichromadora longiseta Allgén, 1933

13. Hypodontolaimus marleenae Muthumbi & Vincx, 1998 (Indian Ocean, Kenyan coast)

14. Hypodontolaimus mediterraneus ( Brunetti, 1949) ( Italy, Marina di Pisa )

15. Hypodontolaimus obtusicaudatus Allgén, 1947 ( USA, San Pedro harbour)

16. Hypodontolaimus pilosus ( Hopper & Meyers, 1967) ( USA, Biscayne Bay)

17. Hypodontolaimus plurisetus Baranova & Dashchenko, 1992 (Pacific Ocean)

18. Hypodontolaimus pumilio Gerlach, 1956 ( Brazil, Pernambuco)

19. Hypodontolaimus punctulatus ( Cobb, 1920) Filipjev, 1934 (Pacific coast of Costa Rica, Punta Arenas)

Syn. Iotadorus punctulatus Cobb, 1920

20. Hypodontolaimus reversus Hopper, 1968 ( Canada, Prince Edward Island)

21. Hypodontolaimus schuurmansstekhoveni Gerlach, 1951 (North Sea, Germany)

22. Hypodontolaimus setosoides Blome, 1982 ( Germany, Sylt)

23. Hypodontolaimus setosus ( Bütschli, 1874) Wieser, 1954 (Kiel Bay, Germany)

Syn. Spiliphera setosa Bütschli, 1874

24. Hypodontolaimus solivagus Hopper, 1963 ( USA, Gulf of Mexico)

25. Hypodontolaimus steineri Wieser, 1954 ( Chile, Tenglo Island)

26. Hypodontolaimus ventrapophyses Huang & Gao, 2016 (Dongshan Island, East China Sea)

SPECIES INQUIRENDA

1. Hypodontolaimus heymonsi ( Steiner, 1921) Filipjev, 1930 (Canary Islands)

Syn. Spiliphera heymonsi Steiner, 1921

2. Hypodontolaimus sivertseni Allgén, 1951 ( Norway, Tautra island)