Female Tail Research Articles

Characterization of three plant or fungal feeding nematodes (Nematoda, Rhabditida, Tylenchomorpha) from coastal dunes in Spain including the SEM study of these species

Three known species, Aphelenchus avenae, Ditylenchus myceliophagus and Tylenchorhynchus aduncus (Rhabditida, Tylenchomorpha), are described from sand coastal dunes in Spain associated to the rhizosphere of xerophilic plants. A. avenae is characterized by having stylet with 16–22 µm long, pharyngeal dorsal gland overlapping the intestine, postvulval uterine sac about 2.5 times the body diameter, female tail short conoid with rounded tip bearing the phasmid and male bursa well developed. D. myceliophagus is characterized by having lateral field with four incisures, stylet 7–8 µm long, basal bulb irregularly pyriform, tail of both sexes similar with rounded tip and bursa of the male reaching about three-quarters of tail length. T. aduncus is characterized by its lateral field with six incisures, stylet 15–18 μm long, spicules with bifurcate tip and distal ventral crest, and gubernaculum with hook-like manubrium. New morphological, including SEM study, and morphometrical data are included for the three species. Also, phylogenetic analysis based on 18S and 28S rDNA is included for two of the species studied. Additionally, two species belonging to the superfamily Aphelenchoidea are transferred to other genera: Aphelenchus assamensis to the genus Aphelenchoides and Aphelenchoides dhanachandi to the genus Potensaphelenchus.

Description of Scutylenchus quercinus n. sp. (Nematoda: Tylenchomorpha) from Asalem forests, north Iran

Summary A new species of Scutylenchus was recovered from soil collected in the rhizosphere of forest trees in natural Asalem forests, Gilan province, north Iran. The new species is described and illustrated based upon morphological and molecular data. Scutylenchus quercinus n. sp. is mainly characterised by having four lines in the lateral fields, thus delimiting it from currently known species of the genus, which have six lines. It is further characterised by 605-709 μm long females having a slightly offset cephalic region with five or six annuli, stylet 19-21 μm long with conus ca 50% of its total length and three slightly posteriorly sloping knobs, vulva in a cavity, with epiptygma, vagina vera squarish in lateral view, female tail subcylindrical with smooth end, and males with 26-30 μm long spicules. The new species was morphologically compared with eight similar species. The molecular phylogenetic relationships of the new species with other relevant species and genera were reconstructed using partial small, large subunit and internal transcribed spacer ribosomal DNA (SSU, LSU D2-D3 and ITS1 rDNA) sequences and the resulting topologies were discussed.

Description of Oscheius cyrus n. sp. (Nematoda: Rhabditidae) as new entomopathogenic nematode from Iran.

A new species of the genus Oscheius, Oscheius cyrus n. sp., collected in the moist soils taken from forest heights in the north of Iran, is recorded. A comprehensive description, comprising molecular (internal transcribed spacer (ITS), 18S, and 28S rDNA genes) information, morphometrics data, light microscope and scanning electron microscope images, is supplied. The species resembles Oscheius myriophilus. However, the highest ranges for female body length, female tail, infective juvenile tail length, median bulb, absence of epiptygma and lateral field incisures number vary. The new species was distinguished from Oscheius insectivorus by the general lip region. The male was not found. Molecular analysis showed that the new species has the most similarity to O. myriophilus both in the ITS and 18S regions. Morphological and molecular data confirmed its belonging to the Insectivora-group. Furthermore, the species of Ochrobactrum pseudogrignonense was reported as a dominant associated bacterium of the new Oscheius species. Finally, the mortality of the host after seven days varied from 20% to 82.5%, depending on nematodes' concentration.

Description of Rotylenchus zhongshanensis sp. nov. (Tylenchomorpha: Hoplolaimidae) and discovery of its endosymbiont Cardinium.

A new bisexual species of Rotylenchus is described and illustrated based on morphological, morphometric and molecular characterizations. Rotylenchus zhongshanensis sp. nov. is characterized by having a conoid lip region complying with the basic pattern for Hoplolaimidae, but with pharyngeal glands slightly overlapping intestine dorsally and cuticle thickened abnormally in female tail terminus. Females have robust stylet (30.1-33.8 μm). The pharyngeal gland has short dorsal (11.2-16.8 μm) overlap on the intestine. The vulva is located at 48.0-56.5% of body length, and phasmids are pore-like, 4-6 annuli posterior to the anus. For males, phasmids are pore-like, 11-17 annuli posterior to cloaca. The spicules are ventrally arcuate (21.0-28.5 μm) with gubernaculum in 5-8 μm length. The rRNA and mitochondrial COI genes were successfully sequenced from the assembled whole-genome sequences of the new species, and were used for reconstructing the phylogenetic relationships of the new species. A new strain of cyto-endosymbiont Cardinium was also discovered from the genome sequences of R. zhongshanensis sp. nov. The 16S rRNA phylogeny analyses revealed that this new bacterial strain is closed to that from cyst and root-lesion nematodes.

New species of Filaria (Nematoda: Filariidae) in the Lesser Grison Galictis cuja (Molina) (Carnivora: Mustelidae) from northern Patagonia, Argentina and comments about the South American species of the genus

Filaria lorenzo n. sp. is described in the Lesser Grison, Galictis cuja from northern Patagonia, Argentina. The new species can be differentiated from the eight species of Filaria from the Old World by the shape of the sclerotized preesophageal ring. The four remaining species of the genus parasitize American Mephitidae and/or Mustelidae. Filaria carvalhoi from Brazil and F. texensis from USA lack a preesophageal ring, whereas F. taxideae from USA and F. conepati from Argentina share with our specimens a preesophageal ring mostly mushroom shaped. Our specimens differ from F. taxideae by lacking lateral alae, by a different ornamentation of the female tail and by the male lacking adcloacal papillae. The new species also differs from F. conepati by the shape of the preesophageal ring and by the shape of the eggs. The indirect examination of the types of F. conepati and F. carvalhoi, corroborated the existence of differences between these two species, allowing us to refute their synonymy, as proposed by some authors. Our results extend the taxonomy of Filaria to 13 species and comprise the first report of a filarioid nematode for an Argentinean mustelid, and the first report for Patagonia.

Redescription of Ektaphelenchoides compsi Baujard, 1984 (Tylenchina: Aphelenchoididae) isolated from Pinus massoniana in Fujian Province, China

Summary Ektaphelenchoides compsi is redescribed morphologically with new molecular characterisation. It was isolated from a dead Pinus massoniana tree in Ningde City, Fujian Province, China. Detailed morphology of the spicule, female gonad, hemizonid position, arrangement of male caudal papillae and female tail terminus shape are documented. It is characterised by a lateral field with three lines (forming two bands), tripartite stylet 17.8 (17.0-19.4) μm long without basal thickenings, metacorpus rectangular with anterior 40% granular and posterior part weakly muscular, metacorpal valve slightly posterior to middle of metacorpus, excretory pore at level of nerve ring, vagina with thickened walls and strongly developed muscular bundles, vulval lips slightly protuberant, vulval flap absent, distal region of post-vulval uterine sac appearing as a weakly developed oogonia, anus and rectum indistinct, female posterior part (‘tail’) dorsally convex, conical, terminal region contracted into a bluntly pointed tip. The spicules are arcuate, 15.6 (14.3-16.3) μm along the chord, lamina smoothly curved to distal end, capitulum slightly concave, condylus well-developed with broadly rounded tip and slightly depressed at dorsal end, rostrum triangular with finely rounded tip, cucullus absent, and with seven caudal papillae present. The near full length 18S and 28S D2-D3 regions of rRNA genes sequences were characterised. The phylogenetic analyses revealed that the Fujian population of E. compsi grouped with the Zhejiang population of E. compsi, both being morphologically identical.

Five new and five known species of the genus Tylencholaimus de Man, 1876 (Nematoda: Dorylaimida: Tylencholaimoidea) from Western Ghats of India

Five new and five known species of the genus Tylencholaimus de Man, 1876 are described from the Western Ghats of India. Tylencholaimus macroamphidius sp. nov. has a 0.61–0.85 mm long body, angular lips, large amphid, 8.0–9.0 μm long odontostyle, odontophore with asymmetrical basal knobs, pharyngeal bulb expanding gradually, female genital system mono-prodelphic, and a rounded to conoid tail. Tylencholaimus shamimi sp. nov. has a 0.57–0.71 mm long body, 6.0–7.0 μm long odontostyle, odontophore with basal thickening, pharyngeal bulb expanding gradually, female genital system amphidelphic and a convex-conoid tail. Tylencholaimus southindicus sp. nov. has a 0.44–0.55 mm long body, lip region with distinct labial disc, 4.5–5.5 μm long odontostyle, odontophore with minute basal knobs, pharyngeal expansion abrupt, female genital system mono-prodelphic, and a rounded-conoid to rounded tail. Tylencholaimus striatus sp. nov. has a 0.30–0.34 mm long body with distinctly striated cuticle, 5.0–5.5 μm long odontostyle, odontophore with minute basal knobs, pharyngeal bulb expanding abruptly, female genital system mono-prodelphic, and a conoid tail with bluntly rounded terminus. Tylencholaimus tamiliensis sp. nov. has 0.51–0.58 mm long body, 5.5–6.0 μm long odontostyle, odontophore with minute basal knobs, pharyngeal bulb expanding gradually, female genital system mono-prodelphic and tail rounded to conoid with sunken terminus. Five known species of the genus Tylencholaimus viz. T. mirabilis, T. teres, T. micronanus, T. ibericus and T. cosmos also recorded from the region and redescribed/illustrated.

Neomisticius platypi n. sp. and N. variabilis n. sp. (Tylenchomorpha: Anguinidae) from dead oak trees in Japan

Summary Two new Neomisticius species, typologically and phylogenetically close to each other, are described and illustrated from dead Quercus trees and an ambrosia beetle, Platypus quercivorus. The two species share some stylet morphological characteristics, namely, they both possess a long conus occupying more than half of the total stylet length, a long crustaformeria composed of more than 160 cells (eight rows of more than 20 cells each), and a short and broad female tail with a digitate tip. They are distinguished from each other by N. variabilis n. sp. having a wide, spindle-shaped male bursa with a blunt terminus and N. platypi n. sp. having an oval bursa with a rounded terminus. In addition, the males and females of both species have three large rectal glands and the posterior end of the male testis (distal end of the vas deferens) bears three cells that seemingly function as a valve between the vas deferens and the cloacal tube. These characteristics have not been reported in other tylenchids. Currently, the genus contains only three species: the two new species and N. rhizomorphoides, which has a normal stylet with a short conus, a short crustaformeria, and lacks rectal glands and valve cells in the vas deferens. Therefore, the two new species are readily distinguished from N. rhizomorphoides and, based on the previous definition, may even represent a new genus. However, considering their phylogenetic closeness and biological similarities (e.g., association with ambrosia beetles), the generic definition of Neomisticius was emended to include these new species.

Two new insect-associated tylenchids, Sychnotylenchus hibisci n. sp. and Neoditylenchus xiphydriae n. sp. (Tylenchomorpha: Anguinidae), from Japan

Summary We isolated two tylenchid species belonging to the Sychnotylenchinae, Sychnotylenchus hibisci n. sp. and Neoditylenchus xiphydriae n. sp., from the bark beetle Ernoporus corpulentus and wood wasp Xiphydria ogasawarai, respectively. Sychnotylenchus hibisci n. sp. is characterised by its moderately stout body in both male and female, gubernaculum to spicule length ratio of one-third or less, crustaformeria structure composed of four columns with six large, rounded cells, and a broad female tail with a rounded terminus. The new species is closely related to S. ulmi, with which it shares body shape and gubernaculum to spicule length ratio, but is distinguished by the female tail shape and several morphometric values. Neoditylenchus xiphydriae n. sp. is characterised by its oval to leaf-shaped male bursa, male tail tip reaching the distal end of, and protruding beyond the bursa, a long post-vulval uterine sac (PUS), and a conical female tail with a narrowly rounded terminus. The species is typologically similar to N. pinophilus but is distinguished by its male spicule shape, gubernaculum to spicule length ratio, and longer PUS. Phylogenetically, the Sychnotylenchinae belongs under the Anguinidae (superfamily Sphaerularioidea) and is closely related to several Ditylenchus, Neotylenchus, Neomisticius, and Ficotylus species.

Devibursaphelenchus alienae n. sp. isolated from the bark of dead Quercus aliena in Japan

Summary A new Devibursaphelenchus species isolated from the bark of a dead Quercus aliena, which had been infected and killed by Japanese oak wilt, was collected in Shiga, Japan. The new species is characterised by the relatively large body in males (661-768 μm) and females (893-1071 μm), conspicuous male bursal flap, male spicule with long condylus and wide blade, female post-vulval uterine sac (PUS) 39-54 μm or 1.6-2.3 times the vulval body diam. long, vestigial female anus, and female tail forming a strongly ventrally recurved elongate conoid with bluntly pointed or narrowly rounded terminus. The new species is typologically similar to D. lini, sharing a large body, conspicuous bursal flap, long PUS, and spicule shape, but can be distinguished from it by the absence of variation in the female tail shape, i.e., the tail of the new species is always long and strongly ventrally curved, while the tail shape varies more in D. lini. A previous molecular phylogenetic analysis suggested that the new species is fairly close to D. lini, but can be distinguished from it by the 1.0% (16 bp) difference within 1.6 kb of the 18S and 3.7% (26 bps) difference within 0.7 kb of the D2-D3 LSU ribosomal RNA genes. The newly found nematode is described and illustrated herein as D. alienae n. sp.

Zerdeçal Tozu İlave Edilmiş Diyetlerin Sarı Kuyruk Çiklit Pseudotropheus acei (Regan 1922)'nin Vücut Pigmentasyonu ve Büyüme Performansı Üzerindeki Etkileri

There are few studies about the effect of turmeric powder on the skin pigmentation of fish in the literature. This study was conducted to research body and tail pigmentation and growth performance of Pseudotropheus acei (Regan 1922) fed supplemented diets with different ratio turmeric (Curcuma longa) powder. Five diets were prepared by adding four different ratios of turmeric powder (T1: 1%, T3: 3%, T5: 5%, and T7: 7% ) to C: control diet (without turmeric powder). A total of 75 broodstock (mean weight 6g) were randomly stocked (4♀:1♂) in 15 aquariums (70x30x40cm), with three replications. The fish were fed twice daily at 8:30 and 20:30 with the diets supplemented turmeric as ad libitum during the 90 days. At the end of the experiment, the body and tail pigmentation of P. acei significantly increased with increasing turmeric rate in diets (P <0.05). The blue indicator –b values in male and female body color were high in all turmeric supplemented groups compared to the control group (P˂0.05). Also, the yellow color indicator + b value in the color of the male and female tail increased with the addition of turmeric. Hab values were determined in the blue area for the body and in the yellow area for the tail. However, pigmentation of all groups supplemented turmeric powder was visually not different from the color of the control group. There were no significant differences between final weights, weight gain SGR, FCR, and survival rates of P. acei fed diets supplemented with turmeric powder compared to the control (P˃0.05). As a result of the study, skin and tail pigmentation and growth performance of P. acei were not improved by supplementing with turmeric powder to diets.

Description of Ruehmaphelenchus taedae n. sp. (Nematoda: Aphelenchoididae) found in Loblolly pine logs from the USA

Summary Ruehmaphelenchus taedae n. sp., isolated from Loblolly pine logs (Pinus taedae L.) from the USA, is described and figured. It is characterised by a relatively slim body (a = 42 and 43 for males and females, respectively), three lines in the lateral field, male spicules relatively small (12-18 μm) with high and dorsally bent condylus and weakly developed rostrum, bursal flap absent, short tail possessing a long terminal spike ending in a bluntly rounded tip and 8.7-13.3 μm long, vulva positioned at ca 83% of body length, vulval flap absent, vulval lips slightly protruding, post-vulval uterine branch extending for less than half of vulva to anus distance, and female tail conoid, ca 3-4 anal body diam. long, with 13.7-18.5 μm terminal projection. The new species can be separated from all other species of the genus by the male tail possessing a long terminal spike and the more anterior excretory pore. Detailed phylogenetic analysis based on 28S D2-D3 region sequences confirmed the status of this nematode as a new species.

Mesodorylaimus ushkaniensis sp. n. and Allodorylaimus baikalensis sp. n. (Nematoda, Dorylaimida) from Lake Baikal, Russia.

Two new nematode species of the order Dorylaimida from Lake Baikal sediments are described and illustrated. Mesodorylaimus ushkaniensis sp. n. is morphologically similar to M. cryptosperma Loof, 1969, but differs by the longer body, comparatively shorter tail in females, longer odontostyle and longer spicules. Allodorylaimus baikalensis sp. n. resembles A. tarkoenensis (Andrássy, 1959) Andrássy, 1986, but differs by the comparatively longer body, tail, spicules, and prerectum in females.

Cryptaphelenchus abietis n. sp. (Tylenchomorpha: Aphelenchoididae) isolated from Cryphalus piceae (Ratzeburg) (Coleoptera: Scolytinae) emerged from Abies veitchii Lindl. (Pinaceae) from Nagano, Japan

Summary An undescribed Cryptaphelenchus species was isolated from a bark beetle, Cryphalus piceae that had emerged from a dead log of the Veitch’s fir, Abies veitchii, collected from Sugadaira Montane Research Center, University of Tsukuba, Nagano, Japan. The new species is characterised by its female post-vulval uterine sac (PUS) of less than one vulval body diam. in length and female posterior body end (tail) conical with elongate posterior part and variably shaped tip, seven male genital papillae, which are composed/arranged as a precloacal P1, P2 pair slightly anterior to cloacal opening, and two small pairs of glandpapillae near tail tip and very narrow bursal flap-like cuticular extension surrounding the male tail. In addition to these characters, the male apophysis appears wing-like in ventral view. In possessing an elongate posterior part, Cryptaphelenchus abietis n. sp. shares the female tail shape with C. borlossi, C. leptocaudus and C. sutoricus, and shares a short PUS with C. iranicus, C. varicaudatus, C. baujardi and C. paravaricaudatus. However, the new species can be distinguished from these species by other typological and morphometric characters and its molecular phylogenetic status. Phylogenetically, the new species is closest to Bursaphelenchus minutus, but can be clearly distinguished by morphological and molecular sequence characters.

Parapharyngodon hispidus n. sp. (Nematoda: Pharyngodonidae) in Tropidurus hispidus (Spix) (Squamata: Tropiduridae) from Caatinga Biome of the Vale do São Francisco, state of Pernambuco, Brazil with a key for the Neotropical species of the genus Parapharyngodon Chatterji.

One species of Parapharyngodon Chatterji (Nematoda: Pharyngodonidae), parasitizing the large intestine of Tropidurus hispidus (Spix) (Squamata: Tropiduridae) in Caatinga biome from Brazil is described and illustrated . This new species differs from a part of its congeners by a set of characters in males: the presence of four pairs of caudal papillae, unpaired post cloacal papilla absent, and smooth anterior cloacal lip. Among the Parapharyngodon species with four pairs caudal papillae, unpaired post clocal papilla absent, and smooth cloacal lips, only P. hispidus n. sp. and P. jairaipurii Rizvi Bursey (Oriental realm), features the same characteristics including sharp pointed tip of spicule, stout terminus or spike of tail of females, and punctate ornamentation of the eggshell. However, these two species are different by the size of spicules (spicules of P. jairaipuri are around 55% of the size spicules of P. hispidus n. sp.); and the arrangement of the caudal papillae (two pairs of adcloacal papillae in P. jaraipuri which are absent in P. hispidus n. sp.). Parapharyngodon hispidus n. sp. is the 55th species assigned to the genus and the 11th species of this genus described in Neotropical hosts.

Bursaphelenchus hibisci n. sp. (Nematoda: Aphelenchoididae) isolated from Ernoporus corpulentus (Scolytinae) emerged from dead Hibiscus tiliaceus (Malvaceae) twigs from Okinawa, Japan

Summary A Bursaphelenchus sp. belonging to the B. idius-group was isolated from a bark beetle, Ernoporus corpulentus, which had emerged from dead twigs of Hibiscus tiliaceus collected in Okinawa, in the subtropical region of Japan. In addition to its group-specific characters, i.e., four lateral lines in both male and female and less developed capitulum and relatively broad blade of the male spicules, the species is characterised by a relatively slender female tail with various tip shapes. Molecularly, the species is close to B. fagi and B. tiliae based on SSU and D2-D3 LSU sequences, but can be clearly distinguished from these two species. The species is described and illustrated herein as B. hibisci n. sp.

Description of Aphelenchoides roulingae n. sp. (Tylenchomorpha: Aphelenchoididae) isolated from Xylocopa collaris sauteri collected from Yilan, Taiwan, with some notes on A. xylocopae Kanzaki, 2006

Summary Aphelenchoides roulingae n. sp. is described and illustrated. This new species was isolated from Xylocopa collaris sauteri collected at Fushan, Yilan county, Taiwan. Typologically, the new species is characterised by a three-lined lateral field, conical female tail with various and not pointed termini, male spicule with well-developed and slightly dorsally truncate condylus, blunt triangular-shaped rostrum and unevenly ventrally curved dorsal contour of the spicule blade (calomus-lamina complex). The combination of typological characters of the new species is unique. Aphelenchoides roulingae n. sp. shares the three-lined lateral field and female tail shape with ‘A. helicus’, which was previously transferred to Robustodorus from Aphelenchoides, but can be differentiated from that species by its longer and more slender female tail, narrower female tail tip, and longer female stylet. In addition, the spicule morphology of A. roulingae n. sp. is unique and not similar to that of any other Aphelenchoides species. Phylogenetically, the new species forms a well-supported clade with the other Xylocopa bee-associated species, A. xylocopae, but can be typologically and molecularly distinguished from the species. In addition to the taxonomic description, some typological characters of the genus Aphelenchoides are discussed.

Molecular phylogenetic study in Spirocercidae (Nematoda) with description of a new species Spirobakerus sagittalis sp. nov. in wild canid Cerdocyon thous from Brazil.

The nematode family Spirocercidae Chitwood and Wehr, 1932, comprises three subfamilies, Spirocercinae Chitwood and Wehr, 1932; Ascaropsinae Alicata and McIntosh, 1933; and Mastophorinae Quentin, 1970, which occur worldwide. Spirocercids infect canids and can cause severe illness. The crab-eating fox, Cerdocyon thous (Linnaeus, 1766), is a canid that inhabits most of South America, including Brazil and is a host for several parasitic worms, in particular, nematodes. However, few reports or genetic data are available on the spirocercids found in this host. In the present study, we describe a new species of Spirobakerus Chabaud and Bain 1981, from the intestine of two crab-eating foxes from two different biomes in Brazil. Spirobakerus sagittalis sp. nov. presents a) unequal spicules, with a long, thin left spicule with a lanceolated shape at the tip; b) a pair of sessile papillae and a median unpaired papillae located anteriorly of the cloaca, and c) a tuft without spines at the tip of the tail in females. The molecular phylogenetic analysis indicated that S. sagittalis sp. nov. is basal to the other species of the subfamily Ascaropsinae, which was not recovered as monophyletic. Our phylogenies also indicated that Spirocercidae is paraphyletic, given that Mastophorinae did not group with Ascaropsinae and Spirocercinae. We provide the first molecular data on the genus Spirobakerus and expand the molecular database of the spirocercids. However, further studies, including the sequences of other spirocercid taxa, are still needed to infer the relationships within this family more accurately.

CAUDOTYLENCHUS INDICUS N. GEN. N. SP. (NEMATODA: TELOTYLENCHIDAE) ASOCIADO CON PLANTA DE BANANO DE BENGALA OCCIDENTAL, INDIA

Caudotylenchus n. gen. es un género de nematodo nuevo elegido bajo la subfamilia Telotylenchinae de la familia Telotylenchidae con la especie tipo Caudotylenchus indicus n. gen., n. sp. Todos los miembros pertenecientes a esta subfamilia son parásitos de plantas en la naturaleza y la actual especie se ha descrito en Bengala Occidental, India, en asociación con el banano (Musa paradisiaca L. cv Chapa). Caudotylenchus indicus n. gen., n. sp. es una pequeña especie de nematodo, mide 0,68-0,85 mm; caracterizado por glándula esofágica superpuesta en forma de maza invertida; región labial estrecha, redondeada-conoide, continua, débilmente esclerotizada; estilete largo con protuberancia basal bien desarrollada, cono y lumen recto; campos laterales marcados con cinco incisiones; ovario didelfo, anfidelfo; vulva en forma de hendidura transversal; extremo de la cola de la hembra sin anillado; bursa simple; y gubernaculum dirigido hacia adelante. Aquí se proporciona una clave taxonómica del nuevo género y el compendio entre trece géneros de la subfamilia.

Effects of inter‐specific crossbreeding between the invasive pine wood nematode, Bursaphelenchus xylophilus and native B. mucronatus on morphology and reproduction of the hybrid offspring

AbstractThe process of inter‐specific hybridization between the invasive, highly pathogenic pinewood nematode, Bursaphelenchus xylophilus and the Eurasian‐native, relatively harmless B. mucronatus has been examined with the aid of the B. xylophilus Roller (Bxy‐rol(tom3) mutation (Tomalak & Filipiak, 2019) as a morphological marker, in the breeding protocol. Validity of the morphologically based selection of the inter‐specific hybrids has been confirmed by examination of individual nematodes with the multiplex PCR technique with specific primers (Filipiak et al., 2017). The research showed that hybridization between both species was possible in F1 and to some extent in subsequent offspring generations. In the general body plan, the hybrids resembled the wild‐type parental species but differed in various morphological/anatomical details. The changes ranged from seemingly indistinct to heavily distorted or occasional missing of particular structures. The most affected were spicules, female tails, the development of gonads and the position of the excretory pore. The hybridization led to various distortions of mating, gametogenesis, embryogenesis and juvenile viability, and development in F1, F2 and subsequent generation offspring, which severely affected the nematode reproductive potential. Potential consequences of the spontaneous inter‐specific hybridization between both species are discussed.