Aphelenchoides lichenicola Siddiqi & Hawksworth, 1982

Girgan, Chantelle, Swart, Antoinette, Marais, Mariette & Fourie, Hendrika, 2018, Aphelenchoides spp. (Nematoda: Aphelenchida) and Panagrolaimus leperisini (Nematoda: Rhabditida) found associated with grass seeds in the Telperion Nature Reserve, South Africa, Zootaxa 4370 (2), pp. 137-155 : 140-143

Aphelenchoides lichenicola Siddiqi & Hawksworth, 1982

( Fig. 1 & 2 )

Aphelenchoides lichenicola was first described from galls found on Cladonia glauca Flörke from Ireland. It was suggested that this species feeds on the fungal component of the lichen ( Siddiqi & Hawksworth, 1982). The original description was the only report found for this species.

Measurements. See Table 4.

Description. Female (n = 1) Habitus: curled in on itself ventrally. Cuticle finely annulated, annule width 1 µm at mid-body. Lateral field 2 µm wide, marked with four incisures ( Fig. 1D ), middle two incisures faint. Head offset ( Fig. 1E ). Lip region 3 µm high and 6 µm broad. Stylet 10 µm long with basal swellings. Lumen of stylet distinct. Median bulb spherical to slightly rectangular ( Fig. 1E ). Valve distinct, situated slightly off centre in posterior half. Nerve ring situated 68 µm from anterior end, less than one corresponding body width from base of median bulb. Excretory pore 73 µm from anterior end, opposite posterior end of nerve ring ( Fig. 1E ). Ovary outstretched with a single row of oocytes ( Fig. 1F & 2E ). Spermatheca oval in shape containing sperm cells ( Fig. 2A ). Vulval lips slightly raised with the vagina occupying more than half the corresponding body width, curving slightly anteriorly ( Fig. 1G ). Post-vulval uterine sac 37 µm in length, about 2.5 times vulval body width and shorter than half the vulva-anus distance ( Fig. 1G & 2C ). Tail elongate conoid, 34 µm long. Terminus bearing slightly star-shaped mucro with central part more prominent ( Fig. 1C & 2B ).

Male (n = 1): Habitus: curled in on itself ventrally. Head, lip region and pharynx as in female ( Fig. 1A ). Stylet 11 µm, longer than in female. Tail 32 µm long with three pairs of subventral papillae ( Fig. 1B ). Mucro similar to female but less star-shaped. Spicules rose-thorn shaped with well-developed apex (18 µm) and rostrum (11 µm), medially measuring 14 µm. Spicules with an anterior subventral concavity and swelling on dorsal limb ( Fig. 1B & 2D ).

Discussion. The female and male specimens of Aphelenchoides found associated with Perotis patens seeds from the Telperion Nature Reserve were identified as A. lichenicola based on the characteristic shape of the spicule (having a concavity in the anterior subterminal surface), tail shape, and presence of four lateral field incisures. The specimens have been positively identified based on measurements and morphology similar to those of Siddiqi & Hawksworth (1982). According to the original description of this species the spicules range between 17 and 18 µm; the specimen described here had a slightly smaller spicule (14 µm). Although smaller in size, the spicules are morphologically the same and it was decided that this specimen is conspecific with A. lichenicola . This species is reported for the first time in South Africa and to our knowledge it is the first report of this species from seeds. Specimens are deposited in the NCN with the accession number 50546.

Siddiqi & Hawksworth, 1982 and Aphelenchoides spicomucronatus Truskova, 1973 .

- indicates structures that were not visible or not present.

Relationships. The Aphelenchoides specimens from Telperion were compared with the following species that are grouped together in the key produced by Shahina (1996). All have a terminal tail outgrowth that is not spine- or star-shaped and four incisures in the lateral field. Females of A. editocaputis Shavrov, 1967 and Aphelenchoides vaughani Maslen, 1979 differ from our specimen in having shorter body (270–320 µm, and 360–430 µm, respectively, compared to 526 µm in our A. lichenicola ). The following species are larger in body length and have different tail shapes: A.hamatus Thorne & Malek, 1968 (1.00 mm, tail with digitate, centrally located hyaline mucro) and A. kungradensis Karimova, 1957 (650 µm, double mucro on tail tip) compared to 526 µm in our A. lichenicola . The following species have a more posterior vulva (V = 70% in A. lichenicola ) and, in cases where males were found, larger spicules (spicule = 14 µm in A. lichenicola ): A. franklini Singh, 1969 (V = 79%, spicule = 23 µm), A. lanceolatus Tandon & Singh, 1974 (V = 71–73%, spicule = 24 µm) and A. rarus Eroshenko, 1968 (V = 72–74%, male unknown).

A. spaskii Eroshenko, 1968 is morphologically the most similar, but differs in tail shape (one long digitate mucro).Other closely related species based on morphology are A. parietinus ( Bastian, 1865) Steiner, 1932 and A. saprophilus Franklin, 1957 . Aphelenchoides parientinus can be differentiated by a longer stylet (11–13) µm vs. 10 µm in A. lichenicola ) and different tail shape (digitate mucro in A. parientinus ). Aphelenchoides saprophilus differs in tail shape (digitate mucro in, A. saprophilus ) spicule size (23 µm vs. 14 µm in A. lichenicola ) and c’ value (3.4 vs. 2.9 in A. lichenicola ).

Figures

FIGURE 1. Aphelenchoides lichenicola. Female (C–G), C: Tail region; D: Lateral field at mid-body; E: Anterior region; F: Anterior end of reproductive system showing arrangement of oocytes; G: Vulval region showing post-vulval uterine sac. Male (A–B), A: Anterior region; B: Tail region showing spicule.

FIGURE 2. Aphelenchoides lichenicola. Female (A–C & E), A: Genital tract with arrow indicating spermatheca with sperm cells; B: Tail region; C: Vulval region showing post-vulval uterine sac; E: Anterior end of reproductive system showing arrangementof oocytes; Male, D: Tail region showing spicule.