Monhysterida

Head of Theristus, photographed by Hanny van Megen.

Belongs within: Nematoda.

The Monhysterida are a group of free-living nematodes, often characterised by their outstretched female reproductive system though this has been shown to occur in members of other nematode lineages.

Characters (from Coomans & Eyualem-Abebe 2006): Small to medium-sized, more or less slender nematodes. Body slightly attenuated towards the rounded or truncated anterior body end, more strongly attenuated towards tail end. Cuticle finely striated (often appearing smooth under light microscopy) or clearly annulated. Anterior sensilla 6 + 10 or 6 + 6 + 4; six inner labial sensilla papilli- or setiform; six outer labial sensilla and four cephalic sensilla usually setiform; setae may be jointed. Amphids typically with round fovea (sometimes described as unispiral or pseudospiral). Dorsal or subdorsal ocelli may be present. Female reproductive system outstretched, either with two ovaries or only one (anterior) ovary. Male reproductive system with either two testes or only one (anterior) testis. Pre-anal genital papillae (supplements) rarely present. Caudal glands mostly confined to tail, opening separately or through a common pore.

<==Monhysterida
    |  i. s.: Daptonema setosum H02
    |--Linhomoeina [Siphonolaimoidea] LB02
    |    |--Linhomoeidae LB02
    |    |--Fusivermidae LB02
    |    `--Siphonolaimus L86 [Siphonolaimidae LB02]
    |         |--S. obscurus Boucher & Helléouet 1977 L86
    |         `--S. tubicen Ott 1972 L86
    `--Monhysterina LB02
         |--Monhysteridae [Monhysteroidea] LB02
         |    |--Monhystera Bastian 1865 E86
         |    |--Diplolaimelloides meyli L02
         |    |--Diplolaimella dievengatensis L02
         |    |--Geomonhystera disjuncta L02
         |    `--Anguimonhystera Andrassy 1981 E86
         |         |--A. ampliceps (Goffart 1950) [=Monhystera ampliceps] E86
         |         |--A. stadleri (Goffart 1950) [=Monhystera stadleri] E86
         |         `--A. tenuissima (Goffart 1950) [=Monhystera tenuissima] E86
         `--Sphaerolaimoidea LB02
              |--Sphaerolaimus [Sphaerolaimidae] LB02
              |    `--S. hirsutus J02
              `--Xyalidae LB02
                   |--Gonionchus australis J02
                   |--Ammotheristus Lorenzen 1977 L86
                   |--Echinotheristus Thun & Riemann 1967 L86
                   |--Pseudosteineria Wieser 1956 L86
                   |--Rhynchonema Cobb 1920 L86
                   |    `--R. chiloense L86
                   |--Prorhynchonema Gourbault 1982 L86
                   |    `--P. warwicki J02
                   |--Steineria Micoletzky 1922 L86
                   |    `--S. ericia Gerlach 1955 L86
                   |--Trichotheristus L86
                   |    |--T. galeatus (Wieser & Hopper 1967) L86
                   |    |--T. mirabilis (Stekhoven & de Coninck 1933) L86
                   |    `--T. paramirabilis (Gerlach 1955) L86
                   `--Theristus Bastian 1865 L86
                        |--T. (Theristus) anisocirculus Blome 1982 L86
                        `--T. (Penzancia) L86
                             |--T. (P.) aculeatus Schulz 1935 L86
                             |--T. (P.) athesinus Andrassy 1962 E86
                             |--T. (P.) monstrosus Gerlach 1954 L86
                             |--T. (P.) ruffoi Andrassy 1959 E86
                             |--T. (P.) vesentinae Andrassy 1962 E86
                             `--T. (P.) wegelinae Andrassy 1962 E86

*Type species of generic name indicated

REFERENCES

Coomans, A., & Eyualem-Abebe. 2006. Order Monhysterida. In: Eyualem-Abebe, W. Traunspurger & I. Andrássy. Freshwater Nematodes: Ecology and Taxonomy pp. 574-603. CABI Publishing.

[E86] Eder, R. 1986. Nematoda from continental subterranean aquatic habitats. In Stygofauna Mundi: A Faunistic, Distributional, and Ecological Synthesis of the World Fauna inhabiting Subterranean Waters (including the Marine Interstitial) (L. Botosaneanu, ed.) pp. 125-132. E. J. Brill / Dr. W. Backhuys: Leiden.

[H02] Hope, I. A. 2002. Embryology, developmental biology and the genome. In The Biology of Nematodes (D. L. Lee, ed.) pp. 121-145. Taylor & Francis: Florence (Kentucky).

[J02] Justine, J.-L. 2002. Male and female gametes and fertilisation. In The Biology of Nematodes (D. L. Lee, ed.) pp. 73-119. Taylor & Francis: Florence (Kentucky).

[L02] Lee, D. L. 2002. Behaviour. In The Biology of Nematodes (D. L. Lee, ed.) pp. 369-387. Taylor & Francis: Florence (Kentucky).

[LB02] Ley, P. de, & M. Blaxter. 2002. Systematic position and phylogeny. In The Biology of Nematodes (D. L. Lee, ed.) pp. 1-30. Taylor & Francis: Florence (Kentucky).

[L86] Lorenzen, S. 1986. Nematoda: Interstitial nematodes from marine brackish and hypersaline environments. In Stygofauna Mundi: A Faunistic, Distributional, and Ecological Synthesis of the World Fauna inhabiting Subterranean Waters (including the Marine Interstitial) (L. Botosaneanu, ed.) pp. 133-142. E. J. Brill / Dr. W. Backhuys: Leiden.