Description of Ruehmaphelenchus juliae n. sp. (Tylenchina: Aphelenchoididae) isolated from an ambrosia beetle, Xylosandrus crassiusculus (Motschulsky), from South Florida

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During a survey of nematode associates of ambrosia beetles from dead and dying red bay and avocado trees affected by the laurel wilt epidemic in southern Florida, a Ruehmaphelenchus species was isolated from the non-native ambrosia beetle, Xylosandrus crassiusculus. The new species is characterised by its possession of an oral disc at the stoma opening, three lines in the lateral field, male spicule with clear dorsal and ventral limbs connected by elongated triangular cuticle, thin membrane-like tissue and cuticular bridge-like structure, conical tail with pointed tip of males and conical tail with digitate mucro of females. The new species is very similar to four previously described species: R. asiaticus, R. digitulus, R. thailandae and R. sirisus, and can be distinguished only by some minor morphological differences in male tail characters, i.e., spicule morphology, position of genital papillae and tail tip shape, and morphometric values. However, the new species is phylogenetically unique, i.e., it is the basal taxon of the Ruehmaphelenchus clade and close to Bursaphelenchus spp. Ruehmaphelenchus juliae n. sp. is therefore proposed based on its morphological diagnostic characters and molecular sequences of near-full-length of SSU, internal transcribed spacer region, D1, D2 and D3 expansion segments of LSU ribosomal RNA and partial mitochondrial COI genes.


International Journal of Fundamental and Applied Nematological Research



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  • Ruehmaphelenchus juliae n. sp. A: Female; B: Male.

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  • Ruehmaphelenchus juliae n. sp. A: Anterior region; B: Lip region and stylet; C: En face view showing oral disc; D: Body surface structure; E: Right lateral view of female gonad; F: Right lateral view of vulval region; G: Ventral view of female anus and rectum; H: Right lateral view of female tail; I: Left lateral view of male tail; J: Ventral view of male tail; K: Left lateral view of spicule; L: Ventral view of spicule; M: Early-stage egg; N: Late-stage egg.

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  • Ruehmaphelenchus juliae n. sp. A: Anterior region (ep = excretory pore; h = hemizonid); B-D: Lip and stylet in different focal planes (od = oral disc). This figure is published in colour in the online edition of this journal, which can be accessed via

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  • Ruehmaphelenchus juliae n. sp. A-C: Right lateral view of male tail in different focal planes; D-F: Left lateral view of spicule (triangular piece is indicated with an arrowhead in E; and bridge connecting dorsal and ventral limb and notch-like separation at distal end of spicule are indicated with arrowheads in F); G-K: Ventral view of male tail in different focal planes. Genital papillae and cloacal opening are labelled P1, P2, P3, P4 and CO. This figure is published in colour in the online edition of this journal, which can be accessed via

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  • Ruehmaphelenchus juliae n. sp. A-C: Right lateral view of female vulval region in different focal planes; D-F: Ventral view of female vulval region in different focal planes; G, H: Left lateral view of female tail in different focal planes; I-L: Early-stage egg in different focal planes; M, N: Late-stage egg in different focal planes. This figure is published in colour in the online edition of this journal, which can be accessed via

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  • Molecular phylogenetic relationships among Ruehmaphelenchus, Sheraphelenchus and Bursaphelenchus species. Bayesian tree inferred from near-full-length of SSU and D2-D3 LSU under GTR + I + G model. lnL = 11 878.3496; freqA = 0.2674; freqC = 0.1694; freqG = 0.2535; freqT = 0.3097; R(a) = 1.4002; R(b) = 2.8221; R(c) = 1.3437; R(d) = 0.7125; R(e) = 5.5059; R(f) = 1; Pinvar = 0.4416; Shape = 0.4562 for near-full-SSU; lnL = 17 794.2188; freqA = 0.1815; freqC = 0.17; freqG = 0.3234; freqT = 0.3251; R(a) = 0.558; R(b) = 2.8917; R(c) = 1.0505; R(d) = 0.6494; R(e) = 4.8359; R(f) = 1; Pinvar = 0.2929; Shape = 0.8046 for D2-D3 LSU. Posterior probability values exceeding 50% are given on appropriate clades.

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