Fergusobia microcarpae, Davies, Kerrie A., Giblin-Davis, Robin M., Ye, Weimin, Taylor, Gary S. & Thomas, W. Kelley, 2013

Davies, Kerrie A., Giblin-Davis, Robin M., Ye, Weimin, Taylor, Gary S. & Thomas, W. Kelley, 2013, Nematodes from galls on Myrtaceae. IV. Fergusobia from flat leaf galls on Eucalyptus and Corymbia, with descriptions of two new species, Zootaxa 3741 (1), pp. 151-171 : 156-160

Fergusobia microcarpae n. sp. Davies

( Figs 3 , 5 B, 6B)

Measurements. Table 2.

Material examined. Holotype, parthenogenetic ♀, Waite Arboretum, Urrbrae, Adelaide, South Australia (34°58´S 138°38´E). From flat leaf galls on Eucalyptus microcarpa Maiden , collected by Kerrie Davies, 29.viii.1996. On slide with a paratype ♂ and infective ♀, deposited at the ANIC, Canberra, ACT, Australia.

Paratypes, WINC, The University of Adelaide, Adelaide, South Australia, slides numbered 0 0 4519, 004853; and the USDA Nematode Collection, Beltsville MD, USA. Taken from flat leaf galls with an unknown species of Fergusonina on E. microcarpa at two locations in South Australia: Waite Arboretum, Urrbrae, 3458´ S 13838 ´E, coll. KD, 2.vii.1997 (WNC 988); roadside vegetation on Strathalbyn to Goolwa road, ~ 60 km south of Adelaide, 3523´ S 13847 ´E, coll. KD and GT, 4.viii.2000 (WNC 2088). Nine parthenogenetic ♀♀, 7 ♂♂, and 1 infective ♀ from the first location. Forty one parthenogenetic ♀♀, eleven pre-parasitic infective ♀♀, twenty three parasitic ♀♀, sixty seven ♂♂ from the second location.

Description. Parthenogenetic female. From flat leaf galls on E. microcarpa . Body C-shaped, more curved when heat relaxed; dorsally curved with ventral side convex; narrowing behind vulva to form a short conoid tail; similar or smaller in size than amphimictic pre-parasitic female and smaller than males. Cuticle obscurely annulated (annules not measured), with longitudinal striae apparent when viewed with light microscope; lateral fields not seen.

Cephalic region diameter 70–80% of body diameter at anterior end, barely offset, 1–2 µm high, unstriated; lateral view with rounded outline and circum-oral area flat. Stylet strongly sclerotised, cone 40–50% of length, basal knobs 2–3 µm across at base, round.

Orifice of dorsal oesophageal gland 1–2 µm posterior to stylet knobs. Anterior fusiform part of digestive tract occupying 59–74% of body diameter (n = 5); lumen of tract broadening near base of dorsal oesophageal gland.

Oesophageal glands large to enormous, occupying ~57–83% (mean 71%) of body diameter (n = 5), extending 38– 62% (mean 50%) of total body length.

Secretory/excretory pore with obscure duct leading to ellipsoid secretory/excretory cell ~8 µm long, so large that it pushes dorsal oesophageal gland aside. Hemizonid 2 or 3 annules in front of secretory/excretory pore.

Reproductive tract variable in length, extending part-way along dorsal oesophageal gland or to nerve ring; may be flexed near the nerve ring or partway along the gland; germinal cell distinctly offset in some specimens; oviduct with oocytes not in rows; uterus containing no eggs or sometimes one (in 4 of 20 specimens examined); vulva flat or a depressed slit, very occasionally with protruding lips (in 1 of 20 specimens). Anus mostly opening into small cuticular depression (in about 50% of specimens) or onto flat surface. Tail short, length 0.9–1.7 times anal body diameter, rounded to bluntly rounded tip.

Infective pre–parasitic female. From flat leaf galls on E. microcarpa . Infecting mature larval stage or pupa of Fergusonina sp. Shape arcuate when relaxed by heat; maximum body diameter at mid-body length, narrowing slightly behind vulva; cuticle with inconspicuous annulations and clear longitudinal striations; lateral fields not seen.

Cephalic region diameter 62–69% of body diameter, barely offset, 1–2 µm long; circum-oral area flat; stylet slender, weakly sclerotised with round basal knobs ~2µm across; cone ~50% of total length.

Orifice of dorsal oesophageal gland 2 µm posterior to stylet knobs. Anterior fusiform part of digestive tract occupying 62–69% of body diameter, length 2.3–2.9 times diameter (n = 3). Oesophageal glands occupying 33– 69% body diameter, extending over intestine to 21–53% body length.

Secretory/excretory pore opening about a third to half way along length of oesophageal glands; secretory/ excretory cell not seen. Hemizonid not seen.

Uterus packed with sperm in inseminated females; vagina perpendicular to body axis, plugged with refractive material; reproductive tract extending to nerve ring, sometimes hypertrophied in length. Vulval lips slightly raised. Tail length approximately equal to body diameter at anus, tip hemispherical.

Parasitic female. From haemolymph in abdomen of adult female Fergusonina sp. Larger than other stages; non-motile. Straight, or slightly dorsally curved when heat-killed; stout. Head not offset. No stylet; no cuticle apparent; oesophagus, intestine and rectum degenerate. Reproductive tract single, greatly hypertrophied in both length and diameter, reflexed and coiled along body length. Vulva a transverse slit at ~85% body length.

Male. From flat leaf galls on E. microcarpa . Body arcuate to J-shaped when relaxed by heat, tail region more or less curved ventrally. Cuticle with obscure annules ~1 µm wide, with longitudinal striae apparent when viewed with light microscope; lateral fields not seen.

Cephalic region diameter 80–90% of anterior body diameter, offset, 1–2 µm long, circum-oral area flat or barely raised, with lightly sclerotised framework; stylet conus ~40% of total length, round stylet knobs ~2 µm across. Anterior fusiform part of digestive tract diameter 62–79% of body diameter, length 1.6–2.3 times diameter (mean 2, n = 5). Oesophageal glands diameter 30–80% (mean 60%) of body diameter, extending over intestine to 32–50% (mean 36%) of total body length. Lumen of intestinal tract broadening posterior to oesophageal gland nucleus.

Secretory/excretory pore opening about opposite nucleus of oesophageal gland; duct obscure; secretory/ excretory cell not seen. Hemizonid 2 annules long, 1 or 2 annules anterior to secretory/excretory pore.

Reproductive tract with single testis, variable in length (extending to nerve ring, overlapping dorsal oesophageal gland or extending to its distal end); outstretched (never reflexed); testis, seminal vesicle and vas deferens not clearly differentiated. Bursa smooth, peloderan; prominent or obscure; arising 24–47% of body length from tail tip. Spicules paired, angular near their middle, relatively slender; lightly sclerotised; manubrium often offset on ventral edge, slightly wider than shaft; blade narrowing gradually to bluntly rounded tip, sometimes with convex curve on proximal edge; opening terminal. Inconspicuous muscles associated with cloaca. Tail ventrally curved, length 1.6–2.8 times diameter at cloaca, with bluntly rounded tip.

Diagnosis and relationships. Fergusobia microcarpae n. sp. is morphologically characterized by the combination of a C-shaped parthenogenetic female with a short, broadly rounded conoid tail, an arcuate to open Cshaped infective female with an hemispherical tail tip, and arcuate to J-shaped males with angular spicules and short peloderan bursa.

Morphologically, F. microcarpae n. sp. is similar to F. porosae n. sp. and F. fisheri . It also has similarities with undescribed Fergusobia collected from flat leaf galls on E. albens and E. siderophloia . From phylogenetic analyses based on sequences of D2/D3 and COI, it is genetically similar to Fergusobia spp. collected from flat leaf galls on Eucalyptus sp. (V 29), F. fisheri (on E. leucoxylon ), F. p o ro s a e n. sp. (on E. porosa ), an undescribed species on E. siderophloia (V’s 24–28) and F. eugenioidae Davies 2012 from flower bud galls on E. eugenioides .

In shape (C-shape), the parthenogenetic female of F. microcarpae n. sp. is similar to that of F. ptychocarpae Taylor & Davies 2008 and F. tumifaciens Currie 1937 . It differs from F. brevicauda Siddiqi 1994 , F. curriei Fisher & Nickle 1968 , F. fasciculosae Davies 2012 , F. fisheri , F. morrisae Davies 2012 , F. nervosae Davies and Giblin- Davis 2004, F. quinquenerviae Davies and Giblin-Davis 2004 (all of which are an open C-shape, i.e. less curved); from F. porosae n. sp., F. camaldulensae Davies 2012 , F. viridiflorae Davies and Giblin-Davis 2004 and F. pohutukawa Taylor, Davies, Martin and Crosby 2007 (which are arcuate to open C-shape, i.e. much less curved); and from F. r i l ey i Davies 2012 (which is almost straight to arcuate). In length (246–360 µm), it is smaller than F. indica (Jairajpuri 1962) Siddiqi 1986 (525–626 µm), and F. magna Siddiqi 1986 sensu Davies 2010 (418–780 µm) (Davies et al. 2010b). The stylet (9.5–11 µm) of these parthenogenetic females is longer than in F. cajuputiae Davies and Giblin-Davis 2004 (8 µm), F. juliae Davies 2012 (5–7 µm), and F. leucadendrae Davies and Giblin- Davis 2004 (8 µm). The vulva (86–91%) is more posterior than in F. eugenioidae Davies 2012 (82–85%), F. jambophila Siddiqi 1986 (81–85%), and F. ptychocarpae (80–85%). Behind the vulva, the body of F. microcarpae n. sp. has a sub-conoid, straight to arcuate shape with a bluntly rounded tip, that differs from that of F. dealbatae Davies and Giblin-Davis 2004 (more slender). It differs from F. fasciculosae in having a narrow conoid tail tip instead of a bluntly rounded one. The length of the tail (11–18 µm) in F. microcarpae n. sp. is shorter than in F. brittenae Davies 2010 (Taylor & Davies 2010) (23–37 µm). The ratio c (16–30) is greater than in F. philippinensis Siddiqi 1994 (9–14) and F. tumifaciens (10–11).

The infective female of F. microcarpae n. sp. is arcuate in shape, similar to F. camaldulensae but differing from that of F. brittenae and F. curriei (open C-shape, i.e. more curved); from F. eugenioidae , F. juliae , F. morrisae , and F ptychocarpae (strongly curved in posterior region); and F. porosae n. sp. and F. rileyi (almost straight). In total body length (302–341 µm), it is smaller than F. magna (537–633 µm) and F. camaldulensae (346–454 µm); and larger than F. leucadendrae (227–291 µm). The stylet length (6–7 µm) is shorter than in F. brevicauda (8–8.5 µm) and F. fasciculosae (8–9 µm), and Fergusobia spp. collected from the M. leucadendra clade. The tail tip (bluntly rounded to hemispherical) differs from that of F. philippinensis (truncate tip). Tail length (13–24 µm) is mostly shorter than in F. fisheri (21–49 µm).

Parasitic females of F. microcarpae n. sp. are smaller (630–675 µm) than those of F. fisheri (690–905 µm), and have a smaller ratio a (respectively, 3.9–5.2 vs 5.9–8.1).

In shape, males of F. microcarpae n. sp. are similar to those of F. eugenioidae , F. fasciculosae , F. porosae n. sp. (all arcuate to C-shaped to barely J-shaped). In F. brittenae , F. curriei , F. juliae , and F. ptychocarpae males are J-shaped; and in F. jambophila males are almost straight. In length (311–398 µm), F. microcarpae n. sp. males are smaller than F. magna (446–588 µm). The morphometric ratio a (9.9–12.5) is greater than in F. tumifaciens (8–9). Stylet length (7–10 µm) is shorter than in F. rileyi (11–13 µm). Tail shape (arcuate, with a bluntly rounded tip) differs from that of F. rileyi (more slender) and F. philippinensis (truncate tip). Tail length (30–48 µm) in male F. microcarpae n. sp. is shorter than in F. pohutukawa (50–61 µm). The ratio c (6.7–11.9) is smaller than in F. quinquenerviae (12.9–17.8). The spicule is more slender in F. microcarpae n. sp. than in F. brevicauda , F. dealbatae , and F. porosae n. sp. The short bursa in F. microcarpae n. sp. differs from that in F. cajuputiae , F. morrisae and F. viridiflorae (where it is long); and F. camaldulensae and F. leucadendrae (where it is of medium length). Morphologically, males of F. microcarpae n. sp. cannot be separated reliably from those of F. fisheri , although the tail of the former is mostly longer (ratio c 6.7–11.9 vs 11–17 in the latter). F. microcarpae n. sp. males are also similar to those of F. fasciculosae , but the cephalic region is larger in diameter relative to the diameter of the body posterior to it (81–90% compared to about 75% for F. fasciculosae ), and the anterior fusiform part of the digestive tract is broader (length 1.6–2.3 times diameter compared to 2.4–3.7 times). Males of F. microcarpae n. sp. and F. nervosae are separated by the position of the hemizonid (1–2 and 5–6 annules anterior to the secretory/ excretory pore, respectively).

Etymology. Named after Eucalyptus microcarpa , the host plant from which the nematodes were collected.

Figures

FIGURE 3. Fergusobia microcarpae n. sp. (all in lateral view): A, Entire parthenogenetic female; B, Head of parthenogenetic female; C, Habitus of parthenogenetic female; D, Tails of parthenogenetic females; E, Entire infective female; F, Head of infective female; G; Habitus of infective female; H, Tails of infective females; I, Entire male; J, Head of male; K, Habitus of males; L, Tails of males. Scale bars: A, E, I = 50 Μm. B, F, J = 5 Μm. C, D, G, H, K, L not drawn to scale.

FIGURE 5. Habitus drawings of Fergusobia spp. (most undescribed) collected from flat leaf galls: A, from E. albens; B, F. microcarpae n. sp. from E. microcarpa; C, from E. odorata; D, F. po ros a e sp. nov from E. porosa; E, F. fisheri from E. leucoxylon; F, from E. siderophloia; G, from C. intermedia; H, from Eucalyptus sp. from Brisbane; I, from Eucalyptus sp. from Lake Tinnaroo. Scale bars = 50 Μm.