Bursaphelenchus talonus ( Thorne, 1935 ), Massey, 1956

Kaisa, T. R., 2003, Redescription of Bursaphelenchus talonus (Thorne, 1935) Massey, 1956 (Nematoda: Parasitaphelenchidae) and designation of lectotypes, Zootaxa 269 (1), pp. 1-7 : 2-6

Bursaphelenchus talonus ( Thorne, 1935)

Massey, 1956 ( Figs. 1­14 )

syn. Aphelenchoides talonus Thorne, 1935

syn. Aphelenchoides (Bursaphelenchus) talonus ( Thorne, 1935) Rühm, 1956

Males: (Measurements are listed in Table 1 ). Body strongly ventrally curved in majority of specimens. Cuticle with fine transverse striae, lateral field with three incisures at midbody. Head offset, lips rounded. Stylet 11 to 14 µm long, basal knobs absent. Procorpus 43 to 52 µm long; metacorpus 14 to 20 µm long by 10 to 12 µm wide with centrally placed valves. Excretory pore not observed. Nerve ring 80 to 94 µm from anterior end. Testis outstretched or reflexed in 22% of specimens examined; flexure 41 to 48 µm long. Spermatogonia­spermatocytes arranged in two rows. Tail arcuate, without mucro; terminus talon­like. Round­ovoid bursa enveloping tail ( Fig. 5 ). Gubernaculum absent. Three pairs of papillae present: first pair pre­cloacal, second and third pairs post­cloacal. Second pair 14 µm from cloaca, third pair 16 µm from cloaca. Spicules mitten­shaped, 15 to 16 µm long; shape variable ( Fig. 14 ). Rostrum pointed, condylus rounded; distance from tip of condylus to tip of rostrum about 9 to 11 µm. Distal tips of spicules pointed, without cucullus.

Females: (Measurements are listed in Table 1 ). Cuticle, head, and lips, same as male. Body slightly ventrally curved posteriorly. Procorpus 47 to 52 µm long; metacorpus 16 to 18 µm long by 12 µm wide with centrally placed valves. Stylet without knobs, 11 to 12 µm long. Excretory pore not observed. Nerve ring 94 to 102 µm from anterior end. Ovary outstretched, oogonia­oocytes arranged in two rows. Spermatheca visible, shape variable; spermatozoa present. Vulva posteriorly situated (V = 72­77), lips slightly protuberant. Vulval flap absent. Postuterine sac 102 to 124 µm long. Tail conoid to bluntly rounded, or sub acute terminus ( Fig. 7 ); mucro absent.

Type host and locality. Associated with mountain pine beetle ( Dendroctonus ponderosae Hopkins ) on lodgepole pine ( Pinus contorta Douglas ), Horse Creek , Utah.

Type specimens. Collected by G. Thorne on 13 June 1933. Hololectotype male , two paralectotype males, and two paralectotype females on slide no. T­ 565t, deposited in the United States Department of Agriculture Nematode Collection ( USDANC), Beltsville, Maryland . Two paralectotype males and one paralectotype female on slide no. T­5115p, deposited in USDANC . Two paralectotype males on slide no. T­5116p, deposited in USDANC . Two paralectotype males on slide no. HWML 44924, deposited in University of Nebraska State Museum , Harold W. Manter Laboratory of Parasitology, Lincoln, Nebraska, USA .

Diagnosis. B. talonus is characterized by three incisures in the lateral field at midbody, a knobless stylet, two rows of oogonia­oocytes and spermatogonia­spermatocytes, and spicules that lack a cucullus. The male tail bears a round­ovoid bursa, three pairs of papillae, and a striking talon­like terminus. The female tail terminus is bluntly rounded or sub acute. A long postuterine sac is present (102­124 µm) and a vulval flap is absent.

Relationships. The following species are similar to B. talonus in spicule morphology and in having three pairs of papillae: B. bestiolus Massey, 1974 ; B. eremus Rühm, 1956 ; B. eucarpus Rühm, 1956 ; and B. nuesslini Rühm, 1956 .

B. bestiolus differs in having a vulval flap, smaller a value in males (32 vs. 37.1­52.6), and smaller c value in males (18.3 vs. 21.8­29.8). B. eremus , B. eucarpus and B. nuesslini differ in having stylet knobs. B. eremus also differs in having males with a larger c value (31­36 vs. 21.8­29.8), and females with a larger a value (41 vs. 34.5­38.8). The same characters also differentiate B. eucarpus from B. talonus . B. eucarpus males have a larger c value (33­45), and females have a larger a value (39­46).

B. incurvus Rühm, 1956 and B. rainulfi Braasch & Burgermeister, 2002 are similar to B. talonus in spicule morphology, but differ in having two pairs of papillae, and stylet knobs. B. rainulfi also differs in having a vulval flap and smaller c value in females (15­20 vs. 23.8­26.1).

B. naujaci Baujard, 1980 was synonymized with B. sexdentati Rühm, 1960 by Tarjan and Baeza Aragon (1982) but was re­established as a valid species by Brzeski and Baujard (1997). It is similar to B. talonus in spicule morphology, and in having three pairs of papillae. It differs in having stylet knobs, a vulval flap, and four incisures in the lateral field.

Bionomics. Thorne (1935) isolated B. talonus from frass in galleries of Dendroctonus ponderosae Hopkins infesting lodgepole pine. Although the biology of the species is unknown, it is probably a phoretic associate of this bark beetle and probably feeds on fungus in galleries constructed by the beetle as reported for other Bursaphelenchus species ( Massey, 1974; Hunt, 1993).

Remarks. Measurements by Thorne (1935) generally agree with those in this study with some exceptions. The postuterine sac was longer in this study than in Thorne’s (102­ 124 µm vs. 96 µm), as was the largest male measured (946 µm vs. 800 µm). However, average male body length was more or less comparable to Thorne’s (758 µm vs. 800 µm). Thorne reported the distance from the anterior end to the nerve ring as 72 µm for the male and 80 µm for the female; these values are much smaller than calculated from his Fig. 5G (97 µm). The value calculated from the figure is within the range obtained for females in this study (94­102 µm), but greater than for males (80­94 µm).

Some morphological observations differed from Thorne’s. In this study, spicule shape was variable ( Fig. 14 ); the condylus was narrower, and the distal tips of spicules were more attenuated than observed by Thorne ( Fig. 14 vs. Fig. 12 ). The ovary was reflexed in Thorne’s study, but not in this study. Flexure of the gonad likely was not observed because few females were studied (n=3), or because it may occur in a few individuals in a population. In this study, two of nine males (22%) had a reflexed gonad.

Figures

FIGURES 1­14. Bursaphelenchus talonus (Thorne, 1935) Massey, 1956. 1, full view of male; 2, full view of female; 3, head and neck of male; 4, male tail; 5, male tail showing bursa; 6, lateral field; 7, variation in female tails; 8, vulval region; 9, head and neck; 10, female tail; 11, male tail; 12, spicules; 13, stylet; 14, variation in spicule shape. Note: 9­12 are redrawn from Thorne, 1935.