Rev 07/14/2026
Chromadorea Rhabditida Rhabditia
Cephalobina Panagrolaimoidea
Chambersiellidae
Microlaiminae
Diastolaimus Rahm, 1928
Type species of genus: Diastolaimus croca (Massey, 1963) Andrassy, 1984
Taxonomic note:
Cid (2012) indicates a total of six species of Diastolaimus, Rahm, 1928. Of those, D. papillatus Rahm, 1928 and 1929 seems to have been moved to Macrolaimus by Goodey (1951) and then to Chambersiella by Sanwal (1960). The type species is indicated as D. croca (Massey, 1963) Andrassy, 1984. Other species include D. grossus (Truskova & Eroshenko, 1977) Andrassy, 1984, D. damalis (Massey, 1966) Andrassy, 1984, D. aculentus (Von Daday, 1905) Andrassy, 1984 and D. mexicana (Cid, 2012). Fescia grossa Truskova & Eroshenko, 1977 was transferred to Diastolaimus as D. grossus by Andrassy (1984)
Cermak et al. (2022) redescribed D. grossus and proposed D. mexicanus as a junior synonym of D. grossus. However, molecular analyses indcate that 28S rRNA gene sequences of D. mexicanus collected from the type and other locations were different from those of D. grossus.
Diastolaimus croca: A, B. Head (a) amphid aperture (s) sensilla pouch; C. Face view; D. Male tail; E. Female midbody; F. Female
Diastolaimus (Santafea) croca, from Massey, 1963
Small to medium-sized nematodes, between 0.8 and 2.3 mm long; cuticle .finely striated.
Lip tregion without cephalic cirri (elaborate projections).
Six prominent cephalic papillae;
Stoma similar to Chambersiella; Cheilorhabdions and protorhahdions distinct, the meso, -meta and telorhabdions fused into a glottid apparatus which extends well back into the precorpus of the esophagus. orsal pharyngeal gland orifice at posterior part of stegostom.Amphids oval, opening at the anterior 1/3 of the telostom.
Pharynx in three parts: a cylindrical corpus, narrow isthmus and terminal muscular valvate bulb. Lateral field marked by two or three incisures.
Tails in both sexes with a hooked terminus and sclerotized mucros..
Female:
Didelphic, ovaries reflexed; two small glands beside vulva lips.
Vulva at mid-body
Male:
Monorchic, testis single straight or reflexed.
A pore on the anterior lip of cloaca in ventral position, presumably for the secretion of the three glands that are anterior to the manubrium.
Precloacal and postcloacal genital papillae variable in number and position.
Spicules paired; gubernaculum anterior part narrow and getting narrower gradually with fine tip.
Diastolaimus-is readily distinguishable from Chambersiella in the absence of cephalic cirri or hairlike setae.
Ref: Massey, 1963; Sanwal, 1971; Cid del Prado et al., 2023
The type specimens were taken from the Sandia Mountains, Cibola National Forest, and the Otowi section of Bandelier National Monument in New Mexico, USA
They were found associated with Scolytus ventralis Lee in Abies concolor (Gord. and Glend.) Lindl. and Phloeosinus sp. in Juniperus osteosperma (Torr.) Little (Massey, 1963).
Food Sources and Feeding strategies for the genus Diastolaimus
Bacterial feeder.
Nematodes in the Chambersiellidae are frequently reported in assocaiation with bark beetles. The relationships are probably phoretic in that the nematodes are transported from tree to tree or to insect galleries by the beetles.
Andrassy, I. 1984. Klasse Nematoda (Ordnungen Monhysterida, Desmocolecida, Araeolaimida, Chromadorida, Rhabditida) Bestimmungsbűcher zur Bodenfauna Europas, No.9. Berlin (Deutschland): Akademie Verlag.
Cermak, V., Njezic, B., Foit, B.J., Kulich, P. Orsagova, H., Ruiz-Cuenca, A.N., Shokoohi, E. Abolafia, J. 2022. Redescription of Diastolaimus grossus (Truskova & Eroshenko, 1977) Andrassy, 1984 (Rhabditida, Chambersiellidae) from Europe and comments on its phylogenetic position. Journal of Helminthology 96e31:1 14.
Cid del Prado Vera, I. 2012. Two new species of nematodes (Cephalobida: Chambersiellidae) from moss from North and South America. Nematropica 42:108-114.
Cid del Prado-Vera, I., Ferris, H. Subbotin, S. A. 2023. A new species of the genus Diastolaimus and redescription of D. mexicanus Cid del Prado, 2012 (Rhabditida: Chambersiellidae) from Mexico. Nematropica 53:30-40.
Goodey, T. 1952. Soil and Freshwater Nematodes: A Monograph. Methuen, London. 390pp.
Massey, C.L. 1963. Santafea new genus (Rhabditoidea, Chambersiellidae) and a change in the systematic position of Macrolaimus Maupas, 1900. Proc. Helminthol. Soc. Wash. 30:26-28.
Rahm, G. F. 1928. Alguns nematodes parasitas e semiparasitas das plantas culturaes do Brasil. Arch. Inst. Biol. Andina Lima, 1 : 239-252.
Rahm, G.F. 1929. Nematodes parasitas e semi-parasitas de diversas plantas culturaes do Brasil. Arch. Inst. Biol. Andina Lima, 1,2: 67-135.
Sanwal, K.C. 1960. Taxonomic position of Macrolaimus papillatus (Rahm, 1928) Goodey, 1951, status of Diastolaimus Rahm, 1928, and emended diagnoses of Chambersiellidae and Chambersiella Cobb, 1920.(Nematoda). Canadian J. Zoology 38:751-753.
Sanwal, K. C. 1971. Geraldius n. gen., Macrolaiminae n. subfam., with a revision of the subfamilies and genera of Chambersiellidae (Nematoda). Canadian J. Zoology 49:965-967.
Truskova, G.M. & Eroshenko, A.S. 1977. Nematodo-fauna vegetativnykh organov travjanistykhi i drevesnykh rastenij elnikov primorja. Trudy Biologio-Pochvennogo Instituta 47, 35-49.
Von Daday, J. 1905. Untersuchungen �ber die S�sswasser-Mikrofauna Paraguays. Zoologica. Stuttgart 18 (44):1-374.