A revised polytomous key for the identification of species of the genusXiphinema Cobb, 1913 (Nematoda: Longidoridae) with exclusion of theX. americanum-group: Supplement 2

Thirty-one species and one subspecies have been described since publication of the first supplement to the polytomous key toXiphinema spp. (see Loof & Luc, 1993). Of these, 11 species belonging to the X. americanum-group are not considered here. Of the 20 remaining species, 13 are considered valid, for which identification codes are given. Three species were described earlier, but had not come to authors' notice; two of them,X. chothecolla andX. clavatus (sic) have already been synonymised withX. radicicola (see Luc & Loof, 1993); codes are given for the third species,X. codiaei. Xiphinema adenohystherum, X. cohni, X. macrogastrum, X. nuragicum andX. sphaerocephalum were considered junior synonyms ofX. pyrenaicum by Baujardet al. (1996);X. hunaniense is considered a junior synonym ofX. radicicola andX. hispanum ofX. aceri. Changes in the group and/or identification codes are made forX. aceri, X. barense, X. dentatum, X. diversicaudatum, X. filicaudatum filicaudatum, X. globosum, X. hardingi, X. paritaliae (= X. dolosum), X. paulistanum, X. pyrenaicum andX. transkeiense. The specific nameX. swarti is emended toX. swartae. Information is given for computerisation of the key.     

Scanning electron microscope observations on the Telotylenchinae Siddiqi, 1960 (Nematoda: Belonolaimidae)

Two species of the genus Trichotylenchus from the semi-arid region of West Africa, T. falciformis, type-species, and T. palustris, previously belonging to the genus Uliginotylenchus, were studied under the scanning electron microscope. Eight characters are common to both species: (i) head continuous with body contour; (ii) four to six cephalic annules present; (iii) first cephalic annule ovoid, laterally elongate and fused with the second cephalic annule at the level of the amphid; (iv) lateral cephalic sectors absent; (v) submedian cephalic sectors dorsally and ventrally fused; (vi) amphidial apertures elongate, ovoid and with longer axis obliquely dorso-ventrally directed; (vii) lateral fields areolated with three incisures; and (viii) spicules with an indentation or a small trapezoidal process on the dorsal side and a short rounded process on the lateral side, both being close to the distal extremity. The synonymy of Uliginotylenchus and Trichotylenchus is confirmed. The definition of Trichotylenchus is amended.     

Ultrastructural Variation of Cuticular Layers in Cephalobinae (Nemata: Rhabditida)

The ultrastructure of the body wall cuticle in Acrobeles complexus, Cervidellus alutus, and Zeldia punctata was studied as a step toward understanding biological diversity within Cephalobinae, and to discover new characters for phylogeny-based classification of the suborder. In each species the cuticle consists of cortical, median, and basal layers. The cortical layer includes an external trilaminate and internal granular zone; the basal layer is striated. In Z. punctata the median layer is electron-lucent, vacuolar, and penetrates the cortical layer; it also includes periodically dense columns that apparently correspond to punctuations visible with light microscopy. In contrast, the median layer of the body wall cuticle in A. complexus and C. alutus is bisected by a zone that undulates parallel to the nematode surface and with periodicity corresponding to annuli. Phylogenetic analysis, using derived cuticle patterns of Cephalobinae, requires an understanding of ecological pressures that could result in convergent evolution of cuticle characters.     

Cuticle Ultrastructure of Criconemella curvata and Criconemella sphaerocephala (Nemata: Criconematidae)

Cuticle ultrastructure of Criconemella curvata and C. sphaerocephala females is presented; males were available only in the second species. Ultrathin sections revealed three major zones: cortical, median, and basal. The cortical zone in the females consists of an external and internal layer. In C. curvata the external layer is trilaminate and at each annule it is covered by a multilayered cap. In C. sphaerocephala the trilaminate layer is lacking and the external cortical layer includes an osmophilic coating. In both species the internal layer consists of alternate striated and unstriated sublayers. The median zone is fibrous with a central lacuna and the zone is interrupted between the annules. The basal zone of the cuticle is striated and narrower between each annule. The cuticle of the C. sphaerocephala male is typical of Tylenchida, except under both lateral fields; the striated layer becomes forked at the first incisure and the innermost two prongs of the fork overlap each other, resulting in a continuous striated band.     

Variabilité intra- et interspécifique des structures cuticulaires externes dans le genre Aorolaimus Sher, 1963 (Nemata: Hoplolaimidae)

Résumé Sept espèces du genre Aorolaimus sont observées au microscope électronique à balayage: A. helicus, A. leiomerus, A. luci, A. macbethi, A. striatus, A. longistylus et A. perscitus. Les résultats montrent que de nombreux caractères morphologiques (forme de la capsule céphalique, présence d'une constriction à la base de la tête, proéminence du disque labial, présence et nombre d'incisures longitudinales sur l'anneau basal de la capsule céphalique, forme de la queue, type d'annélation de la queue, présence de l'épiptygme, présence d'une échancrure à la bursa) présentent une variabilité intraspécifique importante et ne peuvent être utilisés pour la caractérisation des taxons. Certains caractères présentent une variabilité faible: (nombre d'anneaux de la capsule céphalique, présence d'aréolations dans les champs latéraux au niveau de la phasmide, ornementation des champs latéraux), mais sont relativement constants au niveau générique et ne constituent pas un bon critère d'identification spécifique; ils permettent cependant de séparer les espèces en groupes.La morphologie de l'épiptygme est étudiée: l'épiptygme apparaît comme une structure cuticulaire tubulaire, repliée à l'intérieur du vagin, pouvant être plus ou moins saillante à l'extérieur du corps du nématode.La synonymisation des genres Nectopelta et Peltamigratus avec le genre Aorolaimus est confirmée. Huit nouvelles combinaisons sont proposées: A. areolatus, A. levicaudatus, A. amazonensis, A. cerradoensis, A. raskii, A. paraensis, A. vigiae, A. banoae. A. intermedius est transféré au genre Hoplolaimus comme Hoplolaimus intermedius n. comb.Les 32 espèces du genre sont classées en trois groupes suivant (i) la position respective des phasmides, (ii) la présence d'aréolations dans les champs latéraux au niveau de la phasmide, (iii) le type d'incisures longitudinales dans les champs latéraux.Les différences morphologiques entre les genres Scutellonema et Aorolaimus sont discutées.

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Seven species in the genus Aorolaimus are studied with the steroscan electron microscope: A. helicus, A. leiomerus, A. luci, A. macbethi, A. striatus, A. longistylus and A. perscitus. The results show that many characteristic cuticular features (form of the head, head constriction, prominence of labial disc, presence and number of longitudinal striations on basal lip annule, tail form, form of tail annules, presence of epiptygma, indentation of the bursa) are variable at specific level and cannot be used for specific characterization. Some other characters (number of lip annules, presence of areolations at phasmid level in lateral fields, ornamentation of lateral fields) show a low variability, are relatively constant in the genus, have limited use as identification criteria at the specific level, and help to separate species into groups.Study of the morphology of the epiptygma shows that this organ has a tubular structure which can be retracted and/or coiled into the vagina or protruded from the vulva to varying degrees, appearing in lateral optical section single when flattened or double when the tube is open.The synonymy of Peltamigratus and Nectopelta with Aorolaimus is confirmed. Eight new combinations are proposed: A. areolatus, A. levicaudatus, A. amazonensis, A. cerradoensis, A. raskii, A. paraensis, A. vigiae, A. banoae for species originally in Peltamigratus. A. intermedius is transferred to the genus Hoplolaimus as Hoplolaimus intermedius n. comb.The 32 species of the genus are placed in three groups according to (i) phasmid position, (ii) the presence of areolations at phasmid level in the lateral field, and (iii) the type of longitudinal ornamentations in the lateral fields.Morphological differences between the genera Scutellonema and Aorolaimus are discussed.