Paradorylaimus

Orselli, Lara, Clausi, Mirella & Vinciguerra, Maria Teresa, 2012, The genus Paradorylaimus Andrássy, 1969 (Nematoda: Dorylaimida) with description of three new species from Ecuador, Zootaxa 3302, pp. 25-43 : 39-40

The genus Paradorylaimus

Andrássy (1969) erected the genus Paradorylaimus on the species Dorylaimus parafecundus De Coninck, 1935 (type species), Dorylaimus tenuistriatus Schneider, 1935 and Dorylaimus wilhelmschneideri Andrássy, 1959 . He based its diagnosis mainly on the presence of a short pre-rectum, 10–20 supplements in males and longitudinally striated cuticle. Loof & Coomans (1986), having examined the type specimens of D. parafecundus , having realized that there were no longitudinal ridges in the cuticle, as erroneously described by De Coninck, not considering significant the pre-rectum length nor the number of supplements to define the genus, considered Paradorylaimus synonym of Laimydorus Siddiqi, 1969 ; moreover, they redescribed D. tenuistriatus and attributed it to Laimydorus as well. Andrássy (1988) confirmed the validity of the genus Paradorylaimus , which in his opinion could be distinguished from Laimydorus not only by the shorter pre-rectum but also by the relatively longer odontostyle and the smaller number of supplements, and transferred to this genus also the species Mesodorylaimus jankowskyi Tsalolikhin, 1977 . Notwithstanding such confirmation some species with the above mentioned characteristics were successively described as belonging to Laimydorus ( L. vacillans Loof, 1996 ; L. esquiveli Ahmad & Shaheen, 2004 ; L. cardiacus Banyiamuddin & Ahmad, 2006 ). Jairajpuri & Ahmad (1992) considered Paradorylaimus synonym of Drepanodorylaimus Jairajpuri, 1966 . Vinciguerra (2006) considered this genus valid. Recently Andrássy (2009) confirmed once more his opinion on the validity of the genus Paradorylaimus , which he collocated in the subfamily Afrodorylaiminae of the family Dorylaimidae due to the arrangement of the labial papillae in an anterior circle of 10 and a posterior of 6, as also observed in D. parafecundus and in D. tenuistriatus by Loof & Coomans (1986), arrangement which he considered typical of the subfamily. Andrássy added a further diagnostic character of the genus: the small oval sperm, and transferred to it the three above mentioned species of Laimydorus , while he considered D. tenuistriatus species inquirenda.

Having studied the present South American species, we agree with Andrássy’s opinion on the validity of the genus Paradorylaimus among Dorylaimidae . It must be said that the boundaries between the genera of Dorylaimidae are not always well defined since not all of them possess autapomorphic characters: some genera are characterized only by a unique combination of characters. This is true for Prodorylaimus Andrssy, 1959 , Prodorylaimium Andrássy, 1969 , Laimydorus and Paradorylaimus , each of which shows a combination of characters of its own. On such basis Paradorylaimus differs from Laimydorus in some respects. Another, not minor, characteristic of Paradorylaimus is represented by its geographical distribution: India, Sumatra, Costa Rica, Venezuela, Ecuador, Ivory Coast and Siberia. With the exception of the last locality, all the others were part of the paleocontinent Gondwana. This group of species might have originated there from a common ancestor. In particular, the four species from Ecuador studied by us appear more closely related to P. vacillans and to P. esquiveli , respectively found in Venezuela and in Costa Rica; the central and southern America, therefore, seems to be the main region where this genus has had its evolutionary radiation. The Siberian species, M. jankowskyi , however, though possessing a short pre-rectum, has spermatozoa clearly longer than the largest ones of the species from Ecuador (9–11 Μm, as measured from the original drawing, vs. 1–2.5 Μm) and in our opinion its inclusion in Paradorylaimus is doubtful. The species D. tenuistriatus , however, in our opinion fits well with the generic characters and has been included in the species list.