Revised 11/03/21
Trischistomatidae Zhao, 2011
The genera Tripyla (Bastian, 1865), Trischistoma (Cobb, 1913) and Tripylina (Brzeski, 1963) are in the family Tripylidae (De Man, 1876), which is assigned to either the order Triplonchida (de Ley & Blaxter, 2004) or Enoplida (Andrássy, 2007). Paratripyla has been synonymized with Tripyla and the family Tripylidae currently consists of the genera Tripyla, Tripylella, Tripylina, Trischistoma, Tobrilia and Abunema (Zullini, 2006).
In recent classifications of the Nematoda, the three subfamilies recognized
within the family Tripylidae de Man, 1876, order Enoplida Filipjev, 1929 were
Tripylinae de Man, 1876, Trischistomatinae Andrassy, 2007 and Tobriliinae
Andrassy, 2007 (Andrassy 2007)
The subfamily Tripylinae included the genera
Tripyla
Bastian, 1865,
Tripylina
Brzeski, 1963 and
Tripylella Brzeski &
Winiszewska-Ślipińska, 1993.
The Trischistomatinae had only the genus,
Trischistoma Cobb, 1913, and the Tobriliinae had only one
genus, Tobrilia
Andrassy, 1967.
Phylogenetic analysis of small subunit (SSU)
ribosomal DNA sequences distinguished the clade of
Tripylina
plus
Trischistoma from the monophyletic group
represented by species of Tripyla.
Reconstruction of the evolution of ovary number on the phylogenetic tree
indicates that the monovarial condition envolved in the most recent common
ancestor of the
Tripylina plus
Trischistoma clade (Cid del Prado-Vera
et al.
2010).
Other molecular phylogenies separated
Trischistoma from
the other genera and suggested that it is closely related to the family
Trefusiidae in the order Enoplida (Holterman
et al. 2006; Holterman & Holovachov 2007;
Meldal
et al. 2007; Zhao &
Buckley 2009; van Megen et al.
2009), which has affinities in spicule characteristics,
intestinal tract and muscle arrangement (O. Holovachov, personal communication).
Based on the morphological and molecular evidence
that
Tripyla, the type genus of the Tripylidae,
is not closely related to
Trischistoma
and Tripylina,
Zhao (2011) elevated the subfamily Trischistomatinae to family rank and
transferred
Tripylina into
that family.
Consequently, the family
Tripylidae includes the genera
Tripyla
and
Tripylella while the
Trischistomatidae currently includes the genera
Trischistoma and
Tripylina
(Zhao, 2011; Zhao et al. 2012).
Morphologically and anatomically, the number of gonads, the position, shape and size of the stomatal teeth, and the proximity of whorls of labial and cephalic setae are used to distinguish genera in the Tripylidae and Trischistomatidae.
In the Tripylidae:
Tripyla is diovarial, has a striated cuticle, and the outer labial setae and cephalic setae are well separated;
Tripylella females are diovarial, amphidelphic, and the whorls of outer labial and cephalic setae are very close together so that they appear as a single whorl.
In the Trichistomatidae:
Trischistoma has a single ovary and the outer labial and cephalic setae well separated;
Tripylina has a single ovary, the outer labial and cephalic whorls of setae are close together (Tsalolikhin 1983; Zullini 2006; Cid del Prado-Vera et al. 2010; 2012).
Males of Tripylidae have the spicules surrounded by a muscular sheath, which has
been used to support the suggestion that the family has greater affinity with
the Triplonchida than with the Enoplida (De Ley & Blaxter 2004).
However, Andrassy (2007) retained the family
in the Enoplida and molecular phylogenetic analysis of SSU sequences strongly
supports the relationship with the Enoplida (Zhao & Buckley 2009; Cid del
Prado-Vera et al.
2010).
Spicules in males in the Trischistomatidae are
not surrounded by a muscular sheath (Brzeski 1965; Andrássy 1985).
The pharynx in the Tripylidae and
Trischistomatidae is, in
general, uniformly cylindrical throughout its length with slight enlargement in
the latter portion associated with the
location of the esophageal glands.
There are five esophageal gland nuclei, the dorsal esophageal gland reportedly
opening through the dorsal tooth, the first
pair of subventral glands opening
slightly posterior to that,and the second pair of subventral glands opening near
the nerve ring (Chitwood & Chitwood, 1937). At the base
of the pharynx is a
tri-lobed structure variously termed the cardia or cardiac valve.
Nematodes of the families Tripylidae and
Trischistomatidae are
generalist predators of small aquatic and soil organisms. Many authors have
commented on the freshwater and
wet soil in which these nematodes are found,
and on the nature of their prey based on observation of intestinal contents or
from behavior. Among the recorded prey, as
reviewed and collated by Small
(1987), are nematodes, rotifers and protozoa (Cid del Prado et al., 2012).
Andrássy, I. 1985. A dozen new nematode species from Hungary. Opuscula Zoologica (Budapest), 19: 3-39.
Andrássy, I. 2006. Three new species of the family Tripylidae (Penetrantia: Enoplida) from South America. International Journal of Nematology, 16: 208–216.
Andrássy, I. 2007. Free-living nematodes of Hungary (Nematoda, Errantia), II. Hungarian Natural History Museum, Budapest, Hungary. 496 pp.
Bastian, C.H. 1865. Monograph on the Anguillulidae, or free nematoids, marine, land, and freshwater; with descriptions of 100 new species. Transactions of the Linnean Society of London, 25: 73-184.
Brzeski, M.W. 1963. Nematode genera of the family Tripylidae (Nematoda, Enoplida). Acta Zoologica Cracoviensia, 8: 295-308.
Brzeski, M.W. 1964. Revision der Gattungen Tripyla Bastian und Paratripyla gen. n. (Nematoda, Tripylidae). Annales Zoologici, 22: 157-178.
Brzeski, M.W. 1965. On the identity of Trischistoma Cobb and Tripylina Brzeski. Nematologica, 11: 449.
Brzeski, M.W. & Winiszewska-Slipinska, G. 1993. Taxonomy of Tripylidae (Nematoda, Enoplia). Nematologica, 39: 12-52.
Chitwood, B.G. & Chitwood, M.B. 1937. The histology of nemic oesophagi. VIII. The pharynx of representatives of the Enoplida. Journal of the Washington Academy of Sciences, 27: 517-531.
Cid del Prado, I.,
H. Ferris and S.A. Nadler. 2010.
Soil inhabiting nematodes of the genera
Trischistoma,
Tripylina and
Tripyla from México and the
Cid del Prado Vera, I., Ferris, H., Nadler, S.A., Lamothe Argumedo, R. 2012. Four new species of Tripylina Brzeski, 1963 (Enoplida: Tripylidae) from México, with an emended diagnosis of the genus. Journal of Nematode Morphology and Systematics 15: 71-86.
Cid del Prado-Vera, I., Ferris, H., Nadler, S.A. 2016. Five new species of the genus Tripylella (Nematoda: Enoplida: Tripylidae). Zootaxa 4109(2):198-217
Cid del Prado-Vera, I., Ferris, H., Nadler, S.A. 2016. Five new species of the family Trischistomatidae (Nematoda: Enoplida) from North and Central America, with keys to the species of Trischistoma and Tripylina. Zootaxa 4109(2):173-197
Cobb, N.A. 1913. New nematode genera found inhabiting fresh water and non-brackish soils. Journal of Washington Academy of Sciences, 3: 432-445.
De Ley, P. & Blaxter, M. 2004. A new system for Nematoda, combining morphological characters with molecular trees, and translating clades into ranks and taxa. Nematology Monographs and Perspectives, 2: 633-653.
De Man, J.G. 1876. Onderzooekingen over vrij in de aarde levende nematoden. Tijdschrift der Nederlandische Dierkundige Vereeniging, 2: 1-119.
De Man, J.G. 1880. Die elnheimischen, frei in der reinen Erde und im süssen Wasser lebenden Nematoden. Tijdschrift der Nederlandische Dierkundige Vereeniging, 5: 1-104.
Holterman, M. & Holovachov, O. 2007. Phylogeny and biogeography of Triplonchida. Phytopathology, 97(S):132.
Holterman, M.; van der Wurff , A.; van den Elsen, S.; van Megen, H.; Bongers, T.; Holovac hov, O.; Bakker, J. & Helder, J. 2006. Phylum-wide analysis of SSU Trischistoma, Tripylina and rDNA reveals deep phylogenetic relationships among nematodes and accelerated evolution toward crown clades. Molecular Biology and Evolution, 23: 1792-1800.
Small, R.W. 1987. A review of the prey of predatory soil nematodes. Pedobiologia, 30: 179-206.
Tsalolikhin, S.J. 1983. [Nematode Families Tobrilidae and Tripylidae of the World Fauna.] Nauka, Leningrad, Russia, 232 pp. (In Russian).
Zhao, Z.Q. (2011) A review of the genus Trischistoma Cobb, 1913 (Nematoda: Enoplida), with descriptions of four new species from New Zealand. Zootaxa, 3045, 1–25.
Zullini, A. 2006. Order Triplonchida. In: Eyualem-Abebe, I. Andrássy & W. Traunspurger (Eds), Freshwater Nematodes, Ecology and Taxonomy: 293-323. CABI Publishing, Wallingford, UK.