Laimaphelenchus australis Zhao, Davies, Riley & Nobbs, 2006, sp. nov.

Laimaphelenchus australis sp. nov.

Figs. 1–16

Measurements

See Table 1.

Material examined

Holotype, ɗ, Dartmoor, Victoria, Australia (37°48’ S, 141°12’ E). Taken from a sample of bark from P. r a d i a t a. Coll. Zeng Qi Zhao, 3.iv.2005. It has been deposited in the Australian National Insect Collection (ANIC) (slide no. 113).

Paratypes, Waite Insect and Nematode Collection (WINC), The University of Adelaide, slide numbers 004653–004669, 0 0 4670, 0 0 4673, 0 0 4674, 004676–004678. Thirteen males and 17 females were examined and measured. Taken from five locations including: Kuitpo and Mt Gambier, South Australia; Dartmoor and Ballarat, Victoria; and Tumut, NSW.

Description

Female. Short, relatively stout (ratio a range 24.2–31.6) nematodes; habitus ventrally arcuate, with curvature more pronounced in posterior region (Fig. 2). Cuticular debris from a previous moult retained on posterior body in some specimens. Body annules about 0.8 µm wide at mid­body. Lateral fields (Fig. 14) with 4 incisures, occupying about 15% of body width, not areolate, extending to origin of tubercle.

Cephalic region rounded, offset, slightly wider than body at base (Fig. 7). SEM shows labial area with hemispherical sphere, no labial disc, smooth, oral aperture flattened (Fig. 13). Cephalic region with six labial sectors of equal width, amalgamated, separated by double, well­developed ribs. Cephalids not seen. Stylet slender with distinct basal swellings, 9.2–12.3 µm long.

Median bulb rounded to oval, 11.5–14.6 µm long, and 9.2–12.3 µm wide, with crescentic valves in the middle, located 41.5–51.5 µm from the anterior end; its length 3.1–4.6 µm, width 2.7–3.8 µm. The nerve ring is located about one body width from the excretory pore at the point where the lumen of the intestinal tract widens.

Excretory pore conspicuous, about one and a half body widths posterior to median bulb, 70.8–84.6 µm from anterior end. Hemizonid not seen.

Oesophageal glands overlap intestine on dorsal side, extending for 115.4–147.7 µm. Oesophago­intestinal junction 1–1.5 body widths posterior to base of bulb.

Reproductive system with outstretched ovary with oocytes in a single row; spermatheca filled with sperm cells; vagina sloping slightly towards anterior, not distally sclerotised. Post vulval uterine sac 21.5–44.6 µm long, occupying 22–41% of distance from vulva to anus; containing few cells. Vulva without anterior flap; in some specimens appears slightly protruding (Figs. 5, 15).

Tail conoid, ventrally curved, with a single offset terminus, bearing 3–4 pedunculate tubercles, ending with 4–6 finger­like protrusions (Figs. 8, 16).

Male. Morphology similar to that of female (Figs. 1, 9). Testis outstretched, spermatocytes in one single column. Spicules paired, dorsal limb 21.5–26.9 µm long, ventral limb 13.1–16.9 µm long, from distal to proximal end 15.4–19.2 µm long and 16.9–20.8 µm measured along median line; rosethorn­shaped, with prominent capitulum and rostrum broad with bluntly rounded tip (Figs. 4, 10). No gubernaculum present. Caudal papillae located at three positions: first pair preanal subventral, second pair postanal subventral, at about 40–45% of distance between cloaca to tail tip, and third pair at about 75–80% of distance between cloaca to tail tip (Fig. 12).

Tail conoid, ventrally curved, with a single offset terminus, bearing 3–4 pedunculate tubercles, ending with 4–6 finger­like protrusions (Fig. 11).

Diagnosis

Laimaphelenchus australis sp. nov. is characterised by having a distinct tail shape with an offset terminus, with 3–4 clearly pedunculate tubercles ending in 4–6 finger­like protrusions which curve towards the nematode body in both sexes; lateral fields with four lines; off set head; three pairs of subventral caudal papillae, one pair preanal, one pair at about 40–45% of distance between cloaca to tail end, and one pair at about 75–80% of distance between cloaca to tail end. The cephalic region lacks a distinct labial disc, and has six labial sectors of equal width, amalgamated, separated by pairs of well­developed ribs.

Relationships

The genus Laimaphelenchus contains two groups of species, one with a vulval flap and one without (Baujard 1981; Hunt 1993). Lamaphelenchus australis sp. nov. belongs to the second group, bringing its members to five. The other species in this group are L. pannocaudus Massey, L. phloesini Massey, L. pini Baujard, and L. patulus Swart. Laimaphelenchus australis sp. nov. is separated from L. penardi Steiner, L. deconincki Elmiligy and Geraert, L. pensobrinus Massey, L. cocuccii Doucet, L. unituberculus Bajaj and Walia, L. helicosoma Peneva and Chipev, and L. preissii Zhao, Davies, Riley and Nobbs by the absence of a vulval flap in the former.

Females of L. australis sp. nov. (371.5–459.2 µm) are close to L. pini (350–470 µm) (Baujard 1981), L. patulus (460–530 µm) (Swart 1997) and L. phloeosini (430–510 µm) (Massey 1974) in body length. They are shorter than all other described species; L. penardi (573–800 µm) (Filipipjev and Schuurmans Stekhoven 1941), L. deconincki (690–770 µm) (Elmiligy and Geraert 1972), L. pensobrinus (610 µm) (Massey 1966); L. pannocaudus (960 µm) (Massey 1966); L. cocuccii (570–740 µm) (Doucet 1992); L. unituberculus (690–800 µm) (Bajaj and Walia 2000), L. helicosoma (619 µm) (Peneva and Chipev 1999), and L. preissii (1007–1385 µm) (Zhao et al. 2006).

The length of the post­uterine sac of L. australis sp. nov. (20–52 µm) (Swart 1997) overlaps that of L. phloeosini (28–50 µm) (Elmiligy and Geraert 1972), L. pini (18–30 µm) (Baujard 1981), L. patulus (25–40 µm) (Swart 1997), L. deconincki (32–46 µm) (Elmiligy and Geraert 1972), L. cocuccii (40–63 µm) (Doucet 1992), L. unituberculus (45–60 µm) (Bajaj and Walia 2000), L. pensobrinus (37–44 µm) (Massey 1966) and L. helicosoma (21 µm) (Peneva and Chipev 1999); but is shorter than that of L. pannocaudus (82–103 µm) (Massey 1966), L. penardi (72–173 µm) (Filipipjev and Schuurmans Stekhoven 1941) and L. preissii (86–157 µm) (Zhao et al. 2006).

The vagina is surrounded by a relatively thin cuticularised tube, which is similar to most species in the genus, but it differs from L. deconincki which has a thick cuticularised tube (Elmiligy and Geraert 1972).

With respect to the lateral field, L. australis sp. nov. has 4 incisures as do L. pannocaudus, L. unituberculus L. pini, L. preissiii and L. phloeosini. It differs from L. penardi and P. pensobrinus that have 2 incisures and L. patulus, L. helicosoma, L. cocuccii, L. deconincki with 3.

In general, the morphology of the tail tip of L. australis sp. nov. is similar to all described species of the genus, except L. helicosoma which has poorly developed tubercles (Peneva and Chipev 1999), L. unituberculus which has a single stalked suckerlike tubercle (Bajaj and Walia 2000), and L. preissii which has a broad tubercle with many tiny projections (Zhao et al. 2006).

In L. australis sp. nov., the labial disc is reduced and amalgamated with the head capsule, the anterior lip is smooth, and the oral aperture is flattened. Its cephalic region has six labial sectors of equal width, which are amalgamated but separated by pairs of welldeveloped ribs. In this, it differs from all species in the genus except that of L. cocuccii (Doucet 1992). However, L. australis sp. nov. can be differentiated from L. cocuccii by the absence of the vulval flap.

In addition to the differences in the anterior lip between L. australis sp. nov. and L. pini, they also can be differentiated by the position of the oesophago­intestinal junction. In L. pini, the oesophago­intestinal junction is immediately posterior to the base of the bulb (Baujard 1981) but in L. australis sp. nov., it is 1–1.5 body widths behind the bulb.

Males of L. australis sp. nov. (300.8–411.5 µm) are shorter than the female in body length. The spicule shape is similar to that of L. patulus, but it differs in that no gubernaculum­like structure is present at the distal end of spicules (Swart 1997). Three pairs of subventral caudal papillae are present; one pair preanal, a second pair subventral at about 40–45% of the distance from the cloaca to the tail tip, and a third pair at about 75–80% of the distance from the cloaca to the tail terminal. This is similar to all species in the genus in terms of the number of the papillae except L. pensobrinus and L. preissii that have 2 pairs of caudal papillae (Massey 1966; Zhao et al. 2006) and L. cocuccii where males are unknown (Doucet 1992). The male of L. preissii also has a bursa, lacking in L. australis sp. nov. The labial plate and the tail shape are the same as in the female.

Etymology

Named for Australia, the country where it was first isolated.