Fergusobia viminalisae Davies

Davies, Kerrie A., Ye, Weimin, Giblin-Davis, Robin M., Taylor, Gary S., Hodda, Mike & Thomas, W. Kelley, 2014, Nematodes from galls on Myrtaceae. VII. Fergusobia from ‘ leafy’ leaf bud galls in Australia, with re-description of Fergusobia tumifaciens (Currie 1937) Wachek 1955 and descriptions of Fergusobia planchonianae n. sp. and Fergusobia viminalisae n. sp., Zootaxa 3856 (4), pp. 529-554: 544-549

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Fergusobia viminalisae Davies


Description of Fergusobia viminalisae Davies   n. sp.

( Figs 5 View FIGURE 5 ; 6 C,D; 7 B; 8 B)

= Fergusobia   MSp. 11 apud Davies et al., 2010 a

Measurements. Table 4.

Material examined. The description presented here is based on measurements of 29 parthenogenetic ♀s, 22 infective ♀s and 52 ♂ s; Wittunga Botanic Gardens, Blackwood, SA, Australia (3502.12 ’S 13861.01 ’E) ( WINC 0 63737 WNC 938); Loftia Park, Stirling, SA, Australia (3500.55 ”S 13844.10 E) ( WINC 0 63738 and 026038– 40 WNC 974 and 2064); Cleland Conservation Park, Mt. Lofty, SA, Australia (3458.0S 13841.8 E) ( WINC 026044–026046 WNC 2062); and Rickaby Road, Scott Creek, SA, Australia (3506 ’ S 13870 View Materials ’E) ( WINC 004368– 9 WNC 2283). Taken from ‘leafy’ leaf bud galls on Eucalyptus viminalis Labill 1806   growing in bushland or in roadside vegetation. Coll. KA Davies, respectively 7.iii. 1995; 8.ix. 1996 and 21.ix. 1999; 21.ix. 1999; 7.ix. 2002; 9.xi. 2002; and 17.i. 2004.

Holotype. One parthenogenetic female, on a slide deposited in the ANIC, Canberra, ACT, Australia, collection data as above for Rickaby Road, Scott Creek, SA; with a paratype infective ♀ and a ♂.

Paratypes. Vouchers (collection data as above) deposited at the WINC, The University of Adelaide, SA, Australia, 20 parthenogenetic females, 18 infective females and 40 males on slides ( WNC 938, 974, 2064, 2062, 2283); and at the USDA Nematode Collection, Beltsville, MD, USA 5 parthenogenetic females, 3 infective females and 10 males on slides.

Other material examined. About 20 parthenogenetic females and various juveniles from gall forms on E. viminalis   as above, from TAS; roadside vegetation nr. Scottsdale, coll. K.A. Davies, 9.xi. 2002 ( WINC 0 0 4724, WNC 2310).

Description. Parthenogenetic female. From ‘leafy’ leaf bud galls on E. viminalis   . Body open C to C-shape when heat-relaxed, dorsally curved with ventral side convex; similar in size to amphimictic pre-parasitic females and smaller than males; body conoid behind vulva; maximum body diameter frequently in posterior half of body. Cuticle smooth, obscurely annulated, striae apparent with light microscope. Lateral fields appearing ribbon-like under light microscope, under SEM appearing slightly raised, with weak diagonal striae, 2 or 3 µm wide at midbody, narrowing slightly at level of vulva and ending near anus.

Cephalic region 63–69 % diameter of body at anterior end, usually off-set, 1.5–2.5 µm long; unstriated; rounded outline in lateral view; circum-oral area slightly raised. Stylet conus 50 % of total length, basal knobs round, well defined, 2–3 µm wide at base.

Orifice of dorsal pharyngeal gland ca 2 µm posterior to stylet knobs. Anterior fusiform part of digestive tract diameter about 60–75 % of body diameter, length 1.5–2.3 times diameter; lumen of tract broadening at about 80 % length of dorsal pharyngeal gland towards posterior end. Pharyngeal glands enormous, overlapping intestine; diameter 50–90 % of body diameter, distance from head to end of glands being 35–67 % of total body length.

Secretory/excretory pore opening opposite anterior half of dorsal gland, with inconspicuous duct; secretory/ excretory cell ovoid, ca 5 µm long. Hemizonid 2–4 annules anterior to secretory/excretory pore, extending over 2 or 3 annules.

Reproductive tract length variable, usually extending to nerve ring (anterior to it in one specimen); sometimes with 1 or 2 flexures (in 4 / 29 specimens examined); oviduct usually with two or more oocytes per row; uterus mostly containing no eggs but sometimes one egg (in 7 / 29 specimens examined); vulva a depressed slit. Tail conoid with small volume, length and diameter variable, length about 1–1.5 times anal body diameter, tip bluntly rounded.

Infective pre-parasitic female. From ‘leafy’ leaf bud gall on E. viminalis   . Infecting mature larval stage of Fergusonina   sp. or pupa. Body arcuate when relaxed by heat, with most curvature behind vulva; maximum body diameter near mid-body length or vulva. Cuticle inconspicuously annulated, longitudinal striations prominent; lateral fields obscure.

Cephalic region barely off-set. Circum-oral area flat; stylet slender, weakly sclerotised, conus 50 % of total length, with round basal knobs 2–3 µm wide.

Orifice of dorsal pharyngeal gland about 1–2 µm posterior to stylet knobs; pharyngeal glands extending over intestine, diameter 40–70 % body diameter, distance from head to end of glands 38 (31–45)% of total body length. Anterior fusiform part of digestive tract diameter 50–67 % of body diameter.

Secretory/excretory pore opens at mid-length of pharyngeal glands; secretory/excretory cell not seen. Hemizonid extending over two annules, 5 annules anterior to pore.

Uterus 30 % of total gonad length in uninseminated females, packed with sperm in inseminated females; vagina perpendicular to body axis, plugged with refractive material; reproductive tract extending to nerve ring; sometimes hypertrophied. Vulval lips flat or slightly raised. Tail length about 1–1.5 times anal body diameter, tip broadly rounded.

Parasitic female. In haemocoel of abdomen of fly, Fergusonina   sp. Body shape arcuate with broad, bluntly rounded head and tail tips. Head continuous. No cuticle or stylet; oesophagus, intestine and rectum degenerate. Reproductive tract single, greatly hypertrophied, reflexed to coil along body length. Vulva a transverse slit at 70 – 90 % of body length from anterior.

Male. From ‘leafy’ leaf bud galls on E. viminalis   . Body almost straight to J or open C-shaped when heatrelaxed, tail region more or less curved ventrally. Cuticle weakly annulated, annules about 1.2 µm wide, with longitudinal striations; lateral fields 3–4 µm wide at mid-body, flat, non-areolated, anterior end obscure.

Cephalic region off-set, circum-oral area flat, raised or depressed, with lightly sclerotised framework; stylet conus 50 % of total length, round stylet knobs 2–3 µm wide. Anterior fusiform part of digestive tract diameter about 60–75 % of body diameter. Pharyngeal glands extending over intestine, diameter about 70 % of body diameter, distance from head to end of glands being 43 (37–52)% of total body length. Lumen of intestinal tract broadens abruptly midway along length of dorsal pharyngeal gland.

Secretory/excretory pore opens at about 30 % of length of pharyngeal gland towards posterior; secretory/ excretory cell 5 µm long. Hemizonid extending over two annules, 2–4 annules in front of secretory/excretory pore).

Testis single, length variable, extending to nerve ring or overlapping dorsal pharyngeal gland; outstretched or reflexed; testis, seminal vesicle and vas deferens clearly differentiated in specimens with short vas deferens; vas deferens length variable, muscular region small or obscure. Bursa peloderan, smooth, membranous; usually obscure; extending anteriorly 30 – 40 % of body length from tail; posterior end just anterior to tail tip. Spicules paired, angled near middle, usually slender, not heavily sclerotised; manubrium diameter similar or wider than shaft; blade slightly concave on anterior edge; opening obscure. Inconspicuous muscles associated with cloaca. Tail length 1–1.5 times body diameter at cloaca, broadly rounded to almost hemispherical tip.

Diagnosis and relationships. Fergusobia viminalisae   n. sp. is morphologically characterized by the combination of an open C-shaped parthenogenetic female with a small broadly conoid tail, a C-shaped infective female with a bluntly rounded tail tip, and an arcuate to J-shaped male with angular spicules not heavily sclerotised and short to mid-length peloderan bursa.

Morphologically, Fergusobia viminalisae   n. sp. is similar to F. tumifaciens   , F. microcarpae   and F. porosae   .

From phylogenetic analyses based on sequences of 28 S rDNA D 2 /D 3, it is close to F. tumifaciens   from ‘leafy’ LBGs on E. bridgesiana   with 3 -bp differences in 852 -bp sequenced DNA fragment.

Parthenogenetic females of F. viminalisae   n. sp. differ (open C) from that of F. cosmophyllae   , F. floribundae   , F. indica   , F. magna   , F. morr isae   , and F. ptychocarpae   (C-shape); from F. fasciculosae   (arcuate); and from F. rileyi   (almost straight to arcuate). In F. v i m i n al i s a e n. sp., the parthenogenetic female is longer (285–404 µm) than in F. cajuputiae   (221–273 µm). The stylet (9–10.5 µm) is longer than in F. curriei   (5–8 µm), F. juliae   (5–7 µm), F. minimus   (4–8 µm), and F. morrisae   (7–8 µm); and shorter than in F. camaldulensae   (11–13 µm). In has enormous pharyngeal glands (b’ 1.5–2.9), thus differing from F. brevicauda   and F. jambophila   , which have smaller glands, and from F. quinquenerviae   which has larger glands with an extra lobe or flex. In F. viminalisae   n. sp., the vulva is more posterior (V= 86–92 %) than in F. curriei   (78–84 %), F. indica   (71–84 %), F. jambophila   (81–85 %), F. nervosae   (81–83 %), F. pimpamensis   (76–85 %), and F. ptychocarpae   (80–85 %). The body behind the vulva narrows gradually, is arcuate and conoid in shape with a bluntly rounded tail tip, thus differing from that of F. camaldulensae   , F. colbrani   , F. fasciculosae   , F. brevicauda   , F. cajuputiae   , F. leucadendrae   , and F. viridiflorae   (with broadly rounded tips); from F. pohutukawa   (straight, conoid); from F. brittenae   , F. dealbatae   , F. delegatensae   , F. eugenioidae   , F. morrisae   , F. philippinensis   , and F. ptychocarpae   (more slender, arcuate to straight); and from F. diversifoliae   and F. planchonianae   n. sp. (body narrows rapidly behind the vulva). The tail (11–27 µm) of the parthenogenetic female of F. viminalisae   n. sp. is shorter than in F. indica   (50 – 65 µm) and F. magna   (44–96 µm). The ratio c’ (1–1.7) is smaller than in F. philippinensis   (1.9–2.3). The parthenogenetic female of F. viminalisae   n. sp. is generally similar to F. f i s h e r i and F. microcarpae   , but can be separated from them by the position of the hemizonid (respectively, 2–4 vs 7–8 and 1–2 annules anterior to the excretory/secretory pore). The parthenogenetic female of F. viminalisae   n. sp. can be separated from that of F. po ro s a e only by the shape of the conoid tail, which usually has a broader base giving it an apparently larger volume than in the latter. It can be separated from F. tumifaciens   by size of the cephalic region, which is only about half the head diameter in F. tumifaciens   but 63–69 % in F. viminalisae   n. sp.

The infective female of F. viminalisae   n. sp. (arcuate with a strongly curved posterior region) differs in shape from F. brittenae   (open C-shape); from F. brevicauda   , F. camaldulensae   , F. colbrani   , F. curriei   , F. delegatensae   , F. diversifoliae   , F. fisheri   , F. leucadendrae   , F. microcarpae   , F. quinquenerviae   , and F. viridiflorae   (arcuate to just J), and from F. rileyi   (almost straight). It is shorter (length 334–437 µm) than the female of F. magna   (537–633 µm); and larger than those of F. cajuputiae   (239–309 µm), F. leucadendrae   (227–291 µm), F. po ro s ae (277–300 µm), and F. quinquenerviae   (259–325 µm). The ratio a (7.3–11.9, mean 7.6) is larger than in F. cosmophyllae   (4–6.8) and is mostly smaller than in F. floribundae   (10.7–13.6, mean 12.0). Stylet length (7–10 µm) is longer than in F. minimus   (4–6 µm). The infective female F. viminalisae   n. sp. has a broadly rounded tail tip, separating it from F. philippinensis   , with a truncate tip. It has a flat circum-oral area rather than the raised form in F. eugenioidae   . The anterior fusiform part of the pharynx (diameter is 50–76 % of body diameter) is broader than in the female of F. juliae   (diameter 13–28 % of body diameter). The pharyngeal gland in F. v i m i n al i s a e n. sp. is larger than in F. morrisae   (respectively, b’ ratio is 2.7–4.4 vs 4.4–6.9). It lacks the post-anal intestinal sac that is present in F. planchonianae   n. sp. Morphologically, it is difficult to separate the infective female of F. viminalisae   n. sp., F. pimpamensis   n. sp. and F. ptychocarpae   . The tail of F. viminalisae   n. sp. is usually longer compared to the width (c’ ratio of 0.8–1.6, mean 1.2) than in F. ptychocarpae   (c’ ratio 0.6–0.9, mean 0.8) and F. pimpamensis   (c ’ ratio of 1.5–2.4, mean 2.1). Fergusobia viminalisae   n. sp. has stronger curvature of the tail region, and greater body length than in F. viridiflorae   (respectively, 334–437 µm vs 307–347 µm).

The male of F. viminalisae   n. sp. does not differ from that of other described species of Fergusobia   in shape. It is longer (337–462 µm) than the male of F. nervosae   (277–312 µm). The ratio a (8.5–11.6) is smaller than in the male of F. pohutukawa   (12.2–15.5). The stylet (7–10 µm) is shorter than in F. tumifaciens   (12 µm) and F. rileyi   (11–13 µm); and mostly longer than in F. floribundae   (5–8 µm) and F. minimus   (4–7 µm). The tail shape (arcuate with a broadly rounded tip) differs from that of F. philippinensis   (truncate tip); from F. leucadendrae   (bluntly rounded tip); and from F. viridiflorae   (slender, straight to arcuate). The tail (22–35 µm) is shorter than in male F. curriei   (36–38 µm) and F. magna   (54–87 µm). The ratio c (11.4–17.3) of the male of F. viminalisae   n. sp. is greater than in F. cajuputiae   (6.8–9.6), F. dealbatae   (8.3–10), F. leucadendrae   (7.1–10.9), F. microcarpae   (6.7–11.9), and F. ptychocarpae   (7.6–8.6). The ratio c’ (1.1–1.6) is smaller than in F. jambophila   (1.7–2.5). Spicule length (10–15 µm) is shorter than in F. brevicauda   (21–27 µm), F. brittenae   (19–25 µm), F. camaldulensae   (18–22 µm), F. colbrani   (17–21 µm), F. dealbatae   (18–22 µm), F. eugenioidae   (23–25 µm), F. juliae   (20–27 µm), F. morrisae   (18–23 µm), F. planchonianae   n. sp. (18–23.5 µm), F. pohutukawa   (19–24 µm), F. ptychocarpae   (19–21 µm), and F. quinquenerviae   (16–20 µm). The angular spicule of F. viminalisae   n. sp. differs from the arcuate form in F. jambophila   and F. pimpamensis   . The bursa is short (originating 30–40 % of body length anterior to the tail tip and extending to the tip), differing from F. diversifoliae   in which it is longer (arising near the secretory/excretory pore), and from F. delegatensae   in which it ends just posterior to the cloaca. The hemizonid position separates the male of F. viminalisae   n. sp. and F. cosmophyllae   and F. porosae   (respectively, 2–4 vs 10 and 4–5 annules in front of the secretory/excretory pore).

Etymology. Named after E. viminalis   , the host plant from which the nematodes were collected.

TABLE 4. Measurements (µm) of Fergusobia viminalisae n. sp. from E. viminalis. (mean ± standard deviation (range )).

    13.4±1.4 (11.4–14.9)    

Waite Insect and Nematode Collection


Australian National Insect Collection


United States Department of Agriculture


Department of Natural Resources, Environment, The Arts and Sport