Labial Probolae Research Articles

Characterisation of four species of the genus Acrobeloides Cobb, 1924 (Rhabditida, Cephalobidae) from xeric areas in Spain, with revision of the genus and restoration of Paracephalobus Akhtar, 1962

New material of four Acrobeloides species (Acrobeloides arenicola, Acrobeloides bodenheimeri, Acrobeloides nanus and Acrobeloides tricornis) are redescribed from xeric areas in Spain. This species are morphological (based on light microscopy and scanning electron microscopy study) and morphometrically differentiated in two groups. One of them, including A. arenicola, A. nanus and A. tricornis (belonging to the buetschli-group), are characterised by having smaller body, lip region with labial probolae having rectangular base, pharynx with long isthmus, female genital system scarcely developed with vulva midventral, and usually males absent, these with small spicules. Other species group, including A. bodenheimeri (belonging to the maximus-group), is characterised by having longer body, lip region with triangular base, pharynx with very short isthmus, female genital system well developed with vulva usually located ventrolateral, and males frequent with large and robust spicules. This division is corroborate with molecular analyses based on 18S and 28S rDNA. According to this, the separation of the genus Acrobeloides in two different genera is proposed. As Paracephalobus litoralis is morphologically similar to the species of the maximus-group, the genus Paracephalobus is restored to name the species included in the maximus-group. An updated list of species for the genera Acrobeloides and Paracephalobus is included. In addition, Acrobeloides insignis, A. sexlineatus, A. thornei and A. varius are proposed new junior synonyms of A. tricornis.

Morphological and molecular characterisation of two free-living bacterivorous nematodes belonging to Rhabditida from South Africa

AbstractA new population of Pseudacrobeles (Pseudacrobeles) macrocystis and Poikilolaimus oxycercus is described from South Africa. Poikilolaimus oxycercus was collected from soil covered by a natural grass in South Africa, which is morphologically similar to the original description. The South African population of P. oxycercus is characterised by having a small size (807–818 µm in males and 703–779 µm in males), female tail cupola-shaped (24–35 µm), and spicule length (27–35 µm). The South African population of P. (P.) macrocystis, collected from natural grass, is characterised by having a small size (611–786 µm), a lateral field with three incisures, lip region with lips bearing seta-like processes and blunt conoid labial probolae, primary and secondary axils smooth, nerve ring and excretory pore at the posterior part of the pharyngeal corpus, spermatheca well developed, postvulval uterine sac poorly developed, female tail conoid-elongate, male tail conoid with thin acute mucro and spicules small (31–36 µm). Measurements and line illustrations of the species are given. In addition, LM, SEM photographs and the phylogenetic position of P. (P.) macrocyctis are provided. The 18S and 28S rDNA analyses show that P. macrocystis is closely related to other species of the genus Pseudacrobeles having lips with seta-like processes. This is the first report of P. (P.) macrocystis from South Africa.

Comparative morphological and molecular analyses of Acrobeloides bodenheimeri and A. tricornis Cobb, 1924 (Rhabditida, Cephalobidae) from Tunisia

Summary Four populations of Acrobeloides nematodes were isolated from Tunisian soils. Based on morphological and morphometric data, two populations, TC9 and HWO, were identified as A. tricornis and the other two, TC7 and K18g, as A. bodenheimeri. Acrobeloides tricornis is distinguished from its closely related species by its high labial probolae with arcuate termini, inconspicuous post-uterine sac, and five lateral incisures, while A. bodenheimeri is distinguished from other acrobeloids by having a low and rounded labial probolae, distinct post-uterine sac, five lateral incisures, and vulva frequently with vaginal plug. The A. tricornis and A. bodenheimeri reported in this study are distinguished by the shape of labial probolae (high with acute distal part vs low and rounded), post-uterine sac (inconspicuous vs distinct), position of the reproductive system with respect to the intestine (sinistral vs dextral), vulva with vaginal plug (present vs absent) and some morphometric characters (such as body length). Further, these species were also molecularly characterised using the sequences of the D2-D3 region of the 28S rRNA gene, the 18S rRNA gene, the ITS rRNA gene, and of the mitochondrial cytochrome c oxidase subunit I (mtCO1) gene. Phylogenetic trees using ribosomal RNA gene sequences clearly separate species of the ‘Maximus’ group, but these sequences appear to be identical in several other Acrobeloides species, and thus are unlikely to be useful as molecular markers for species-level molecular identification in the genus Acrobeloides. The mtCO1 gene sequences of two A. tricornis populations differ in 58 and 64 nucleotide bases from A. varius and A. nanus, respectively, indicating that the mtCO1 gene sequences have greater phylogenetic resolving power than nuclear rRNA gene sequences, and that this gene marker can differentiate closely related species in the genus Acrobeloides.

Description of Spinocephalus tessellatus n. gen., n. sp. (Rhabditida, Cephalobidae) from Iran, a nematode with a new morphological pattern at lip region.

A new genus and new species of the family Cephalobidae, subfamily Cephalobinae, named Spinocephalus tessellatus n. gen., n. sp. is described from Iran. Body 0.55–0.67 mm long, cuticle with tessellations, lateral field with two tessellated longitudinal wings, lip region with six triangular lips, primary axils deep and V-shaped with two conoid-elongate guard processes that originate from each lip, secondary axils deep and U-shaped with one thorn-like process (labial probolae?) in lateral view with a small rounded protuberance fused to the oral plate having triradiate symmetry more developed at the acute margin toward each primary axil, oral opening hexagonal, amphids large and clearly rounded to slightly oval, stoma cephaloboid with cheilostom with minute and rounded rhabdia, pharynx cephaloboid with corpus subcylindrical and isthmus very long being 1.4–1.7 times corpus length, nerve ring surrounds the isthmus, excretory pore at the level of the isthmus. Female monodelphic-prodelphic, spermatheca as long as the body diam., post-vulval uterine sac 0.8–1.0 times body diameter, tail conoid with small rounded terminus. Male monorchic, spicules 24–26 µm long, gubernaculum 11–14 µm long, tail conical and ventrally curved with small rounded terminus. Morphological, including SEM observations, and molecular (based on 18S and 28S rDNA) analyses revealed its relationship with the genera Acromoldavicus and Nothacrobeles.

Characterization ofNothacrobeles lanceolatusAbolafia & Peña-Santiago, 2003 (Rhabditida, Cephalobidae), a typical species of coastal dunes from Spain

AbstractThe nematodeNothacrobeles lanceolatuswas described in arid soils from Cabo de Gata-Níjar Natural Park, province of Almería (Spain). Since then this species has not been found again. In this study, new data on the distribution and morphological, morphometrical and molecular characteristics (based on 18S and 28S ribosomal DNA) ofN.lanceolatusis provided. This species is characterized by having a tessellated cuticle, with its inner layer bearing two rows of cuticular punctations per annulus, lips quadrangular with eight pinnae, labial probolae bifurcate with divergent prongs surrounded by pinnae, pharynx with corpus 2.5–4.0 times isthmus length, post-vulval uterine sac 1.4–2.2 times the corresponding body diameter, and female and male tails conical, bearing a conical mucro with acute terminus. The phylogenetic position of this and related species of the genusNothacrobelesis discussed. Additionally, bacteria (Pasteuria) and fungi (Catenaria,Nematocida) feeding onN.lanceolatusare showed including light microscopy and scanning electron microscopy illustrations.

Redescription of Paracrobeles laterellus Heyns, 1968 (Rhabditida: Cephalobidae) from Botswana

Summary Paracrobeles laterellus is redescribed from the North-West District (Koanaka Hill), Botswana, which forms part of the Kalahari Desert. A scanning electron microscopy study of the species is presented for the first time. This population is characterised by its adult body length, lateral field with three longitudinal incisures, lips with three tines, the middle one being shorter, primary and secondary axils with two guard processes, labial probolae bifurcate with basal ridge and smooth prongs, pharynx with very swollen and elongate metacorpus, spermatheca swollen, post-vulval uterine sac well developed, vagina sigmoid, female and male tails conoid, and characters of the spicules and gubernaculum. Morphologically, P. laterellus is very similar to P. kelsodunensis and P. mojavicus according to the morphology of the lip region, i.e., with two guard processes at the primary axils and robust spicules.

Description of Acrobeles aenigmaticus sp. n. (Rhabditida: Cephalobidae), an unusual species with a poorly developed vulva, from the Kalahari Desert (Ngamiland, Botswana)

Summary Acrobeles aenigmaticus sp. n. is described from the North-West District (Ngamiland) of Botswana, which forms part of the Kalahari Desert. This new species is characterised by its body length, ‘double’ cuticle bearing numerous interannular punctations, lateral fields with two longitudinal incisures, lips triangular bearing triangular tines with variation in their morphology, labial probolae bifurcated with prongs bearing triangular tines, pharyngeal corpus 2.8-3.8 times the isthmus length, spermatheca 0.8-1.8 times the body diam., post-vulval sac 1.3-2.2 times the body diam., vagina bent to the left side, vulva located left subventral and very reduced, female tail conoid-elongate, male tail conoid, spicules 24-29 μm and gubernaculum 13-17 μm in length. Molecular characterisation of 18S and 28S rRNA shows the relationship of this species with other species of Acrobeles that also present a ‘double’ cuticle, as well as with other cephalobids (e.g., Cervidellus alutus) with the same characteristic in terms of its cuticle.

On the identity of Chiloplacus subtenuis Rashid & Heyns, 1990 and C. tenuis Rashid & Heyns, 1990 (Rhabditida: Cephalobidae), with description of C. mysteriosus sp. n.

Type material ofChiloplacus subtenuisandC. tenuiswas studied and Iberian material originally described asC. tenuisre-examined. The results provided relevant new information to elucidate the identity of these species with more accuracy. On studying their type material, new features and details ofC. subtenuisandC. tenuiswere observed concerning the nature of the lip margin, morphology of the labial probolae, the lateral field at vulval level, and the orientation of the vulva (ventral or subventral). Re-examination of Iberian material ofC. tenuisrevealed that it consists of specimens belonging to three taxa:C. tenuis,C. membranifer, and an unknown species described and named herein asC. mysteriosussp. n. The morphology of lip region in representatives ofChiloplacusis analysed and discussed.Zeldiaspannatais transferred toChiloplacusasC. spannatuscomb. n. andChiloplacus juniperiis regarded as a junior synonym ofNothacrobeles nanocorpus.

Acrobeloides varius sp. n. (Rhabditida: Cephalobidae) from South Korea

A newAcrobeloidesis described and illustrated from samples collected in rice farmland in South Korea.Acrobeloides variussp. n. exhibits morphological characters of other acrobeloids, including a corpus with elongate spindle-like swelling and lateral incisures that extend to the tail end region. However, this new species is distinguished from other acrobeloids by having lateral incisures that change in number from one to five, three low rounded labial probolae, and a conical pointed tail end with a small spike-shaped mucron. In this study, a detailed morphological comparison ofAcrobeloidesspecies is provided, along with new molecular sequence data from the D2-D3 regions of LSU, SSU and partial mtDNAcox1region from the new species, which can be used as molecular barcode sequences.

First Record of Acrobeloides nanus (Cephalobidae: Rhabditida: Nematoda) from Korea

Acrobeloides nanus (de Man, 1880) Anderson, 1968 belonging to the family Cephalobidae Filpijev, 1934 (Cephalobomorpha) is newly reported from South Korea. This species is distinguished from other Acrobeloides species by its low and blunt labial probolae, five lateral incisures with middle incisure extending to the tail tip, and bluntly rounded tail. In this study, details of morphological characters of A. nanus is described and illustrated based on optical and scanning electron microscopy. In addition, molecular sequence data of the D2-D3 region of 28S rDNA, 18S rDNA and mitochondria DNA cox1 region from this species are provided as DNA barcode sequences.

First record Acrobeles ciliatus (Rhabditida) and Plectus parietinus (Plectida) from South Korea

Acrobeles ciliatus (von Linstow, 1877) and Plectus parietinus (Bastian, 1865) are newly collected from Korea. Acrobeles is similar to those nematode belongs to Rhabditidae and Panagrolaimidae by having terminal bulb without medium bulb but different by having complex, vines shaped labial attachment. A. ciliatus differed from other Acrobeles species by lateral fields with two incisures, primary axils U-shaped, and secondary axils V-shaped. Head region set off with the neck, three high labial probolae present, each having 5 tines at inner margins and 5-7 at outer margins, and two elongate apical tines. Also, it differs from the longer female body. Plectus parietinus is distinguished from all other species of Plectus by the prominent hypodermal glands, the relatively small amphid, the distinct and well set-off lips and by the subdorsal distal caudal seta on the left side of the tail. Stoma without stylet. Oesophagus about 1/4 of total body length with terminal bulb. Anus ca. <TEX>$100{\mu}m$</TEX> from posterior extremity. Vulva is at middle of body. Have spinneret on tail tip.

Description of Trithornus aquatica gen. n. sp. n. (Nemtoda:Cephalobina) from aquatic habitat, India.

Abstract: A new cephalobid nematode, Trithornus aquatica gen. n. sp. n. has been described and illustrated. The new genus can be distinguished by the unique shape of its labial probolae, consisting of swollen labial shaft and a trifurcated apical section. The cephalic probolae is triangular in shape. Cuticle is transversely annulated, lateral field with five incisors, outer ones being undulate. The stoma comprises of cheilostom with granular rhabdia, gymnostom narrower than cheilostom and stegostom. Stegostome can be differentiated into three parts meta, meso and telo. A tooth is present on mesostegostome. Females have cephaloboid type of reproductive system. Tail is elongate conoid with a pointed tip. Males were not found. The newly described genus closely resembles Acrobeles Linstow, 1877, Chiloplacus Thorne, 1937 and Cervidellus Thorne, 1937 in having similar stoma, furcated labial probolae, simple cuticle and cephaloboid type of female gonad with a post uterine sac. But, is clearly distinguishable by the related genera on the basis of the shape of labial probolae and the presence of outer undulated lateral lines. A dichotomous key to the identification of the genus has also been provided.

Re-description of Cephalobus topali Andrássy, 1970 (Rhabditida, Cephalobidae) from Vietnam, and transfer to Acrobeloides (Cobb, 1924) Thorne, 1937.

Recently, specimens of Cephalobus topali, collected from an agricultural area from northern Vietnam, are described, including SEM study. They are characterized by their its 306-347 µm long body in females, lateral field with two alae or 3-4 longitudinal incisures, lip region with three pairs of asymmetrical conoid lips, three low and rounded labial probolae separate from the corresponding pair of lips by an incisure, U-shaped primary axils without guard processes, V-shaped secondary axils without guard processes, pharyngeal corpus slightly fusiform and 2.6-3.1 times the isthmus length, spermatheca and postvulval sac poorly developed, female tail conoid (18-24 µm, c = 12.7-17.0, c' = 1.8-2.7) with rounded terminus ending in an acute or wart-shaped mucro, phasmid at 29-34% of tail length, and male unknown. SEM pictures reveal that lip region pattern significantly differs from that found in members of Cephalobus and fits that observed in Acrobeloides, so that the species is transferred to this genus. Cephalobus quadrilineatus is provisionally maintained as different from C. topali.

An aberrant nematode, Baldwinema n. gen. (Nematoda: Panagrolaimomorpha: Panagrolaimidae), from Iran with description of three new species

A new genus of Panagrolaimidae, together with three new species, is proposed based on morphological, morphometric and molecular studies. Baldwinema n. gen. is unique in the Tylenchina by a combination of the following characters: having valvular median bulb, no valve in terminal pharyngeal bulb and absence of stylet. It is further characterised by cylindrical body, thin and finely annulated cuticle, lateral field with two lines (forming a single plain band), fused lips, small longitudinal amphidial openings located on lateral lips, lip region without labial probolae, with six inner and six outer labial and four cephalic papillae (as seen using SEM images), stoma aberrant, cheilostom and gymnostom of equal length, cheilostom with thin wall, gymnostom with clear and thick wall, and stegostom beginning with a tubular thin wall and ending with a thicker wall. Baldwinema ilamense n. gen., n. sp., the type, is characterised by its short post-vulval uterine sac of 7.7 (6.0-9.0) μm long, female tail length of 147 (120-175) μm, shape of gubernaculum, and arrangement of male genital papillae; B. ardabilense n. gen., n. sp. by its short post-vulval uterine sac of 11.5 (9.0-15.0) μm, female tail length of 150 (136-169) μm, shape of gubernaculum, and arrangement of male genital papillae; and B. golestanense n. gen., n. sp. by its long post-vulval uterine sac of 16 (13-21) μm, female tail length of 200 (174-220) μm, shape of gubernaculum, and arrangement of male genital papillae. Phylogenetic analyses based on sequences of the small subunit (SSU) ribosomal RNA gene showed that the new genus is nested within the Panagrolaimidae. However, LSU data did not demonstrate monophyly of the Panagrolaimidae.

Descriptions of species of Stegelleta Thorne, 1938 (Nematoda, Rhabditida, Cephalobidae) from California, New Zealand and Senegal, and a revision of the genus

Populations of Stegelleta are described from California, New Zealand and Senegal. An amphimictic population from California is identified as belonging to S. incisa and compared with type specimens from Utah and an amphimictic population from Italy. One population from New Zealand is close to S. incisa but considered to represent a new species, Stegelleta laterocornuta sp. nov. It is particularly characterised by a 379–512 μm long body in females and 365–476 μm in males; cuticle divided into 16 rows of blocks at midbody (excluding lateral field); lateral field with four incisures; three pairs of asymmetrical lips, U-shaped primary axils without guarding processes, each lip asymmetrically rectangular with a smooth margin, only lateral lips have slender acute tines; three labial probolae, bifurcated at half of their length; vulva without flap; spermatheca 17–31 μm long; postuterine sac 7–24 μm long; spicules 21.5–23.5 μm long. Other specimens from New Zealand are identified as belonging to S. tuarua. A parthenogenetic population from Senegal is identified as belonging to S. ophioglossa and compared with type specimens from Mongolia and records of several other populations of S. ophioglossa. The generic diagnosis is emended and a key to the species of Stegelleta is provided.

Acrobeloides ishraqi sp. n. and Acrobeloides mushtaqi sp. n. (Nematoda: Rhabditida) from chickpea rhizosphere, Uttar Pradesh, India

Two new species of nematode in the genus Acrobeloides were found from rhizosphere of chickpea from Jhansi and Faizabad districts of Uttar Pradesh, India. Acrobeloides ishraqi sp. n. and A. mushtaqi were identified and described on the basis of morphological observations. Measurement and morphological observation of different stages of A. ishraqi were taken and compared with known species of the genus. Acrobeloides ishraqi sp. n. is closely related to Acrobeloides bodenheimeri (Steiner G. 1936. Opuscula miscellanea nematologica, IV. Proceedings of the Helminthological Society of Washington. Vol. 3. p. 74–80.), Thorne G. 1937. A revision of the nematode family Cephalobidae Chitwood & Chitwood, 1934. Proceedings of Helminth Society, Washington. Vol. 4. p. 1–16; however, it differs in having longer body 0.99–1.19 mm (vs. L = 0.655–0.821mm); longer stoma 15.5–16.49 μm (vs. stoma = 11–13 μm), longer pharyngeal corpus 179.4–223.1 μm (vs. pharynx 140–170 m); larger bulb 24.25–38.8 μm (vs. 19–25 μm); bulb is spherical (vs. ovoid), of lesser a value 10.5–15.8 (vs. a = 16.6–23.5); longer rectum 31.04–42.68 μm. (vs. rectum = 20–27 μm) and absence of males (vs. male present). Tail shape is blunt in sp. n. vs. rounded terminus. A. ishraqi sp. n. also compared with Acrobeloides arenicola (Abolafia J, Pena-Santiago R. 2003. Nematodes of the order Rhabditida from Andalucía Oriental, Spain. The genus Acrobeloides (Cobb, 1924) Thorne, 1937, with description of A. arenicola sp. n. and a key to species. J Nematode Morphol Syst. 5:107–130) but differs in having longer body (vs. c = 9.6–10.5); lesser C1 value (vs. C1 = 3.3 –3.7); lesser number of labial probolae (vs. labial probolae 5); shape of female tail (vs. tail with pointed terminus). A. mushtaqi sp. n. comprises of 0.49–0.79 mm long nematodes, with annulated cuticle all over the body. Body pores are very prominent. Reproductive system monoprodelphic with posteriorly out-stretched ovary extending beyond vulva with single flexure. New species close resemblance to A. bodenheimeri (Steiner G. 1936. Opuscula miscellanea nematologica, IV. Proceedings of the Helminthological Society of Washington. Vol. 3. p. 74–80) Thorne G. 1937. A revision of the nematode family Cephalobidae Chitwood & Chitwood, 1934. Proceedings of Helminth Society, Washington. Vol. 4. p. 1–16, but differs in having prominent body pores, greater a value (vs. a = 16–24 in A. bodenheimeri); lesser number of lateral lines (vs. lateral field with five incisures); difference in lip region n. sp. bears a pair of sensilla (vs. flattened amalgamated lips in A. bodenheimeri).

Cervidellus sonorensis n. sp. (Nematoda: Cephalobidae) from the desert of Anza-Borrego, CA, USA

Abstract Cervidellus sonorensis n. sp. is described from sand near the roots of creosote bush (Larrea tridentata) from Anza-Borrego Desert State Park, CA, USA. It is distinguished from others in the genus by the combination of a greatly distended, guitar-shaped corpus and the morphology of the lips and labial probolae. Distinctive features include a large pharyngeal metacorpus with a double swelling, a knob-like ledge at the base of each labial probola and lips with five filamentous tines, the most apical of which are those closest to the primary axil. One male individual was discovered in this parthenogenetic species. Characters used to diagnose C. sonorensis n. sp. are not definitive with respect to other genera and are probably plesiomorphic or convergent in light of DNA-based phylogenetic hypotheses. The position of C. sonorensis n. sp. and morphologically close congeners in relation to species of Nothacrobeles and Paracrobeles is discussed.

Nematodes of the order Rhabditida from Andalucía Oriental, Spain. The genus Cephalobus Bastian, 1865 with description of C. harpagonis sp. n. and key to species

AbstractA new species of the genus Cephalobus is described from natural areas in the south-eastern Iberian Peninsula. Cephalobus harpagonis sp. n. is characterised by female body length of 0.38-0.47 mm, lips amalgamated in pairs, labial probolae present as low ridges connecting tips of adjacent lips, ovary lacking flexures, spermatheca 11-12 μm long, postuterine sac very short (0.3-0.4 times corresponding body diam.), female tail conical or subcylindrical (22-31 μm, c = 13.2-17.1, c′ = 1.7-2.5) and ending in a tuberculate, often harpoon-like, mucro. Descriptions, measurements and illustrations, including SEM photographs, are also provided for C. persegnis and C. troglophilus from Spain. An identification key to Cephalobus species and a compendium of their measurements are also provided.

Nematodes of the order Rhabditida from Tehran province, Iran. The genus Acrobeles von Linstow, 1877 with description of A. iranicus sp. n.

AbstractA new species of the genus Acrobeles is described from natural areas in Tehran province, Iran. Acrobeles iranicus sp. n. is characterised by having a body 400–441 μ m long in females, 'double' cuticle with rows of interannular punctations, lateral field with two incisures, labial probolae 9–12 μ m long, pharyngeal corpus slightly fusiform and 2–4 times isthmus length, postuterine sac 5–15 μ m or 0.2–0.5 times as long as body diam. and bearing larger cells in its proximal part and conical female tail (31–36 μ m, c = 11.5–13.6, c′ = 2.3–2.9). In addition, Iranian populations of another three previously known species are studied: A. andalusicus, A. complexus and A. singulus, the third species having the male described for the first time. Descriptions, measurements and illustrations, including SEM photographs, are provided for all four species.

Three‐dimensional reconstruction of the nose epidermal cells in the microbial feeding nematode, Acrobeles complexus (Nematoda: Rhabditida)

The epidermis of the anterior end (nose) plays an important role in the evolution, development, and functional feeding morphology in nematodes, but information on this complex organ system is limited. Here, we produce a 3D model of 13 of the cells making up this organ system reconstructed from serial transmission electron micrographs of the microbial feeding nematode, Acrobeles complexus. Nose epidermal cells were found to be broadly similar to those of the distantly related model organism Caenorhabditis elegans in the number and arrangement of nuclei in these largely syncytial cells; this similarity demonstrates striking evolutionary conservation that allows for robust statements of homology between the taxa. Examining details of cell shape, however, revealed surprisingly complex subcellular specialization, which differed markedly from C. elegans in the number and arrangement of cell processes. Anterior toroid processes of the anterior arcade, posterior arcade, and HypB syncytia form a nested complex at the base of the labial probolae. Anterior toroid processes of HypC and the inner labial socket cells are associated with the base of the cephalic probolae and radial ridge processes. Extracellular filaments (tendon organs) and radiating cytoskeletal filaments of the posterior arcade syncytium form a connection between the body wall muscle cells and the pharynx. An epidermal cell with no known homolog in other nematodes is identified. Findings provide a basis to propose hypotheses related to the development and evolutionary origin of specialized feeding appendages (probolae) in the Cephalobinae (including Acrobeles), and hypotheses of homology are revised for epidermal cells in the nose of the closely related and primarily plant parasitic group, Tylenchida.