Contribution to the study of the genus PratyZenchoides Winslow (Nematoda : Tylenchida) James G. BALDWIN*, Michel Luc ** and Arnold H. BELL* * Department of Nematology, University of California, Riverside, Ca 92521, USAand ** Muséum national d’Histoire naturelle, Laboratoire des Vers, 61 rue de Bufion, 75005 Paris, France. SUMMARY The comparative morphology of the oesophagus and lip region of Pratylenchoides is examined. The diagnosis is amended and two new species and a new combination are described. Pratylenchoidesheathi n. sp. resembles P. crenicauda but is distinct with respect to several characters including less overlapof the glands of the oesophagus. Pratylenchoides utahensis n. sp. is similar to P. ritteri but the position of the oesophago-intestinal junction is much further posterior to the isthmus in P. utahensis.Alnplimerlinius magnicauda (Thorne, 1935) Siddiqi, 1976 con- forms to genus Pratylenchoides in spite of a very little overlap of glands ; therefore this species is transferred to Pratylenchoides as P. magnicauda (Thorne, 1935) n. comb. Light microscope observations of the oesophagus of twelve species of Pratylenchoides suggest a morpholagical continuum €rom species with little overlap, including P. magnicauda, to modifications which resultin displacement of the oesophago-intestinal junction toa more anterior position relative to the isthmus, and elongation of one or both subventral glands. Examination of six species of Pratylenchoides by scanning electron microscopy (SEM) indicates that they share a similar lip pattern which is apparently modified from a hexaradiate pattern through fusion of the labial dise withsubmedial lip sectors. Comparison withfour species of Radopholus suggests that Radopholus has a uniquelip pattern distinct from Pratylenchoides. The morphologieal continuum of the oesophagus together with observations of the lip pattern lend support to Pratylenchoides as a monophyletic group. RÉSUMÉ Contribution à l’e‘tude du genre Pratylenchoides Winslow (Nematoda : Tylenchida) Une étude de morphologie comparative a été réalisée chez Pratylenchoides concernant l’œsophage et la région labiale. La diagnose du genre est amendée, deux nouvelles espèces décrites et une nouvelle combinaison proposée. Pratylenchoides heathi n. sp., proche de P. crenicauda, s’en distingue par plusieurs caractères dont le plus faible recouvrement de l’œsophage sur l’intestin. Pratylenchoides utahensis n. sp. est semblable à P. ritteri, mais la posi- tion de la jonction œsophago-intestinale y est située beaucoup plus postérieurement par rapport à l’isthme œso- phagien. Amplimerliniusnzagnicauda (Thorne, 1935) Siddiqi, 1976, malgréun recouvrement œsophago-intes- tinal très faible, est transféré au genre Pratylenchoides, et devient P. magnicauda (Thorne, 1935) n. comb. L’obser- vation en microscopie optiquede l’œsophage chez douzeespèces de Pratylenchoides suggèrel’existence d’un continuummorphologique depuis les espèces ayantun très faible recouvrement cesophago-intestinal, dont P. magnicauda, jusqu’à celles montrant un déplacement de la jonctioncesophago-intestinale vers l’avant accompagnée de l’élongation de l’une ou des deux glandes œsophagiennes subventrales. L’observation au microscope électro- nique à balayage de la région labialechez six espèces de Pratylenchoides a montré une disposition labiale semblable, apparemment dérivée d’une structure hexaradiale parfusion du disque labial avec les secteurs labiaux submédians. Une comparaison sur ce point avec quatre espèces de Radopholus a montré que ce genre a une structure labiale particulière, bien distincte de celle de Pratylenchoides. Le continuum morphologique noté pour l’œsophage ainsi que les observations concernant la structure labiale amènent, à considérer le genre Pratylenchoides comme un groupe monophylétique. * * ‘Nematologist of ORSTOM. Revue Nématol. 6 (1) : 111-125 (1983) 111 J.G. Baldwin, M. Luc dl- A.H. Bell Winslow (1958) proposed the genus Pralylen- We also examined the oesophagealregion of choides, withthe type and only species, P. creni- several Pratylenchoides species with the lightmicros- cauda Winslow, 1958, and placed it in the subfamily cope,as well asthe lip region withthe scanning Pratylenchinae, as the third genus, withPratylenchus electron microscope (SEM). In this latter case com- Filipjev, 1936 and Radopholus Thorne, 1944. The parisons were made with species of Radopholus. originaldiagnosis stated : “Close to Pratylenchus, but didelphic.Differing from Radopholus inthe length of the oesophagealoverlap which is short Material and methods and oblique in Pratylenchoides and Pratylenchus, longer and parallel-sided in Radopholus”. Specimenscollected inUtah were fixed in 5% Sher (1970), in hisrevision of the genus, gave a formalin and infiltrat>edwith glycerin for examination thoroughhistorical account including the relation- with the light microscope and SEM ; mounting for shipsbetween Pratylenchoides and Zygotylenchus SEM was as reported by Sher and Bell (1975). Siddiqi,1963 (syn. : Mesotylus deGuiran, 1964). Of fourteenspecies recognized inthe genus He alsodescribed four new species (P.variabilis, Pratylenchoides [see below)twelve species were P. leiocauda, P. ritteri and P. bacilisemenus) and available from the University of California Riverside redescribed the three known species : P. crenicauda, Nematode Collection (UCRNC) for light microscope P. laticauda Braun & Loof, 1966 and P. maritimus studies of theoesophagus ; thetwo species not Bor & s’Jacob, 1966. studied were P. epacris and P. ivanovae. Sher (1970) rediagnosed the genus, and distinguish- Theseobservations included whole mounts of ed it from the “most closely related genus”, Rado- females in glycerin.Illustrations of,glands were pholus, by a number of characters,namely the preparedfrom specimens which could be oriented presence of deirids, a less pronounced sexual dimor- exactlylateral ; killedspecimens frequently twist phism, and the oesophagus “with at least one oeso- so that the anterior portionis not lateral. In addit.ion, phageal nucleus at or above the level of the oeso- handcut sections through oesophageal glands of phageal intestinal valve”. Sher (1970) also observed somespecies weremounted in glycerin jelly for theabsence of longitudinalmarkings on the lip examination. region incontrast to Radopholus andpointed out The lip region of at least fifteen females as well as that species withthe longestoverlap mostnearly somejuveniles and males of eachnew species and resemble Radopholus species. thenew combination was examined with SEM. The sevenspecies included inSher’s revision Forcomparison, similar SEM observations were suggestamorphological continuum (morphocline) madeon Pratylenchoidescrenicauda, P. bacilise- from species with oesophagealglands thatonly menus, P. ritteri,Radopholus similis Thorne,1949, slightly overlap the intestine, to those with a long R. magniglans Sher,1968, R. rotundisemenus Sher, overlap.This series hasbeen strengthened by 1968, and R. vertexplanus Sher, 1968. Additional subsequentdescriptions of Pratylenchoidesalkani comparisonswere madewith previous unpublished Yüksel,1977, P. erzurumensis Yüksel,1977, P. SEMobservations of otherTylenchida. Glycerin- epacris Eroshenko, 1978, and P. ivanovae Ryss, 1980. infiltrated specimens were coated with about 0.02 ym Seinhorst (1971) did not consider Sher’s revision and gold with a Jeol 5-4 vacuum evaporator and exam- described a morphocline of the oesophagus including ined with a JeolJSM-35C SEM operatedat 5 kV. the three first describedspecies of Pratylenchoides, which al1 have ashort overlap. He considered the variation to occur primarily through lengtheningof a Genus Pratylenchoides Winslow, 1958 subventral gland fromthe primitive (basal bulb) state. Since 1968, A. H. Bell has collected two previously ’ undescribedspecies of Pratylenchoides fromUtah DIAGNOSISAMENDED which contribute to a more complete characterization of the intragenericvariability in the oesophagus. Prat,ylenchidae.Female genital tracts paired. Theyare describedbelow as P. heathi n.sp. and Labial region flattened anteriorly, somewhat conical, P. utahensis n. sp. characterized (with SEM) by the fusion of the labial Specimens of Amplimerlinius magnicauda (Thorne, disc with the submedial sectorsof the first lip annule. 1935) Siddiqi, 1976were collected nearthe type Spear strong with rounded basal knobs.Oesophageal localityin Utah for a reevalution of this species glands overlapping intestine ventrally, laterally and relative to Pratylenchoides species ; observations led dorsally ; greatest development dorsally; overlapping totransfer of this species tothis latter genus as very variable in length ; in somecases (P. magni- Pratylenchoides magnicauda (Thorne, 1935) n. comb. cauda) nearlyabsent. Generally at leastone oeso- 112 Revue Nématol. 6 (1) : 111-125 (1983) Study of the genus Pratylenchoides phageal gland nucleus above or at the level of the on theholotype and on populations from Utah oesophago-intestinalvalve ; insome species, three andColorado. Loof (1971)described a population nuclei posterior to the valve, but in this case two fromSpitzbergen. Siddiqi (1976) examined these posterior nuclei at relatively great distance from the latterspecimens and Utah’s populations ; hegave anterior one (long intestinal overlapping). Oesophago- measurementsas well asa description of afemale intestinal valve well developed. Deirids conspicuous. collected in Utah by Thorne in 1939. Sexual dimorplzism of anterior part of male slight, Al1 thesedescriptions