Fergusobia leucoxylonae Davies

Davies, Kerrie A., Bartholomaeus, Faerlie, Giblin-Davis, Robin M., Ye, Weimin, Taylor, Gary S. & Thomas, W. Kelley, 2014, Nematodes from galls on Myrtaceae. VIII. Fergusobia from small galls on shoot buds, with descriptions of four new species, Zootaxa 3857 (1), pp. 1-40 : 10-15

Fergusobia leucoxylonae Davies n. sp.

( Figs 4 , 7 J, 8K)

= Fergusobia MSp . 17 apud Davies et al. 2010a

Measurements. Table 3 .

Material examined. The description presented here is based on measurements of 22 parthenogenetic ♀s, 8 preparasitic infective ♀s, and 22 ♂ s. From planted and/or roadside trees; Kensington Park, Adelaide, SA, Australia (3455.45S 13839.76E) ( WINC 0 0 4509, WNC 2090); Urrbrae, Adelaide, SA, Australia ( WINC 0 26020, WNC 2200) (3458.14S 13837.92E); Kensington Park, Adelaide, SA, Australia (3455 S 13838 E) ( WINC 0 0 4773, WNC 2227); Kensington Park, Adelaide, SA, Australia (3455.45S 13839.76E) ( WINC 0 0 4805, WNC 2285); Kensington Park, Adelaide, SA, Australia (3455.45S 13839.76E) ( WINC 0 63869, WNC 2467); Stonyfell, Adelaide, SA, Australia (3455.76S 13840.26E) ( WINC 0 63709, WNC 2470 = V 741). Taken from small, usually multilocular and sessile, shoot bud galls on Eucalyptus leucoxylon . Respectively collected by K.A. Davies, 6.viii.2000, G.S. Taylor 9.viii.2000, K.A. Davies 10.ix.2001, K.A. Davies 10.viii.2005, K.A. Davies 20.viii.2005.

Holotype. Parthenogenetic female, on a slide deposited in the ANIC, Canberra, ACT, Australia; together with an infective female and a male; collected at Kensington Park, Kensington Park, Adelaide, South Australia, by K.A. Davies, 6.viii.2000 (WNC 2090).

Paratypes. Vouchers (collection data as above) deposited at the WINC, The University of Adelaide, SA, Australia, 15 parthenogenetic ♀s, 5 pre-parasitic infective ♀s, 15 ♂ s; and at the USDA nematode Collection, Beltsville, MD, USA 6 parthenogenetic ♀s, 2 pre-parasitic infective ♀s, and 6 ♂ s.

Description. Parthenogenetic female. From small shoot bud galls on E. leucoxylon . Body C-shape when heatrelaxed, dorsally curved with ventral side convex, variable in length (170–383 µm); similar in size to pre-parasitic infective female and to male; body conoid behind vulva. Cuticle smooth, annules obscure, appears striated when viewed with light microscope; lateral fields not seen.

Cephalic region 64–72 % diameter of body at anterior end, clearly offset, 1.4–2.2 µm high; unstriated; in lateral view has rounded outline and circum-oral area slightly raised. Stylet 9–11.5 µm long, with conus 30% of total stylet length, basal knobs well defined, round.

Orifice of dorsal pharyngeal gland immediately posterior to stylet knobs. Anterior fusiform part of digestive tract occupying 51–84% of body diameter, 2.2 (1.6–3.0) times diameter in length; lumen of tract broadens at ~ 80% or more length of dorsal pharyngeal gland. Pharyngeal glands extending over intestine, large, ~ 60–80% of body diameter in diameter, distance from head to end of glands being 53 (46–67)% of total body length.

Secretory/excretory pore opens 41–100 µm from anterior end with weakly sclerotised duct; secretory/ excretory cell not seen. Hemizonid at level of or one annule anterior to the pore.

Reproductive tract comprising ovary with growth zone occupying ~ 40–70% of length, structure of oviduct obscure, no spermatheca, quadricolumella present, not smooth, uterine sac ~ 0.5–1 vulval body width in length.

Reproductive tract extending to or part way along pharyngeal gland or to nerve ring; usually with a ventral flexure; growth zone usually with varying numbers of oocytes per row; uterine sac containing no eggs or one egg in 1 of 22 specimens examined; vulva usually a depressed slit, may be flat and with protruding lips in 3 of 22 specimens. Tail variable in length and diameter, conoid with small volume, 1–2.5 times anal body diameter in length, with a rounded tip.

Infective pre-parasitic female. From small shoot bud galls on E. leucoxylon . Penetrates mature larval stage of Fergusonina sp. or pupa. Arcuate shape when relaxed by heat, with slightly more curvature behind vulva; maximum body diameter at mid-body in some or at vulva in other specimens; cuticle appears smooth, annules obscure, longitudinal striae apparent with light microscope; lateral fields not seen.

Cephalic region occupying ~ 60–75 % diameter of body at anterior end, clearly offset, 0.4–1.7 µm high; unstriated; in lateral view has rounded outline and circum-oral area slightly raised. Stylet weakly sclerotised, 7–9 µm long, with conus 30% of total length, and tiny round basal knobs.

Orifice of dorsal pharyngeal gland 1–2 µm posterior to stylet knobs. Anterior fusiform part of digestive tract occupying 46–63% of body diameter. Diameter of pharyngeal glands obscure, extending over intestine, distance from head to end of glands being 32 (20–42)% of total body length.

Secretory/excretory pore opens 61–77 µm behind anterior end, about halfway along length of pharyngeal glands; secretory/excretory cell ovate, ~3 µm long. Hemizonid not seen.

Uterus 50% of total gonad length in uninseminated female, packed with amoeboid sperm in inseminated female; vagina slightly angled towards tail; reproductive tract extending to nerve ring; hypertrophy of tract in some specimens. Vulval lips slightly raised. Tail short, 0.5–1.0 times diameter at anus in length, tip broadly rounded to almost hemispherical.

Male. From small shoot bud galls on E. leucoxylon . Body almost straight to barely J-shaped when relaxed by heat, tail region more or less curved ventrally. Cuticle weakly annulated, longitudinal striae apparent with light microscope; lateral fields not seen.

Cephalic region occupying 64–85% of anterior body diameter, offset, 1.4–2.9 µm high; circum-oral area flat, with lightly sclerotised framework; stylet 7–9 µm long, with conus 30% of total length, round stylet knobs ~ 2 µm wide.

Orifice of dorsal pharyngeal gland less than 1 µm posterior to stylet knobs. Anterior fusiform part of digestive tract occupying 59–87% of body diameter. Pharyngeal glands extending over intestine, occupying ~ 60–80% of body diameter, distance from head to end of glands being 50 (40–67)% of total body length. Lumen of intestinal tract broadens sharply at ~ 50–70% length of dorsal pharyngeal gland.

Secretory/excretory pore opens 60–95 µm behind anterior end, at ~ 30% of length of pharyngeal gland; secretory/excretory cell ovoid, ~ 5 µm long. Hemizonid extending over one or two annules, immediately anterior to secretory/excretory pore.

Reproductive tract with single testis, with varying degrees of development; may be outstretched extending to nerve ring but usually overlaps dorsal pharyngeal gland or is reflexed and does not reach gland; testis, seminal vesicle and vas deferens not clearly differentiated, muscular region of vas deferens small or not apparent. Bursa usually smooth, crenate in 1/ 22 specimens; often obscure; arises 17 – 30% along length of body, apparently ends anterior to tail tip but envelops it in one specimen. Spicules paired, angular at about 60% of length, slender, not heavily sclerotised; manubrium off-set, barely wider than shaft; opening obscure. Large muscles associated with cloaca. Tail length 1 – 2.5 times diameter at cloaca; ventrally curved; with a rounded tip.

Molecular phylogenetic relationships. For molecular analysis, the D2/D3 expansion segments of LSU (V71: AY589360 ) and mitDNA COI (V71: AY589442 , V741: EF 011098 ) were sequenced. Based on the combined data from D2/D3 and COI, V71 ( F. leucoxylonae n. sp.) is sister to V32 (MSp 28) and in a monophyletic clade with V32, V63 ( F. gomphocephalae n. sp.), V65 ( F. fasciculosae ) and V4 ( F. juliae ) ( Ye et al., 2007, Fig. 5 ) with a posterior probability of 100%. Based on COI, V71 and V741 (both F. leucoxylonae n. sp.) are closest and in a monophyletic clade with V740 (MSp 47) and V32 ( Ye et al., 2007, Fig. 4 ). The blastn search of LSU of V71 (851 bp sequenced) revealed it has 10–12-bp differences (99% identity) and 1–2 gaps with V32 ( AY589328 ), V68 ( AY589357 ), V275 ( AY589367 ) and V347 ( AY589397 ). The blastn search of COI (618 bp sequenced) on V71 revealed it has 15-bp differences (98% identity) with V741 and 37-bp differences (94% identity) with V32 ( AY589422 ). Its status as a unique species is corroborated by this data.

Diagnosis and relationships. Fergusobia leucoxylonae n. sp. (MSp 17, Davies et al. 2010a) is morphologically characterized by the combination of a C-shaped parthenogenetic female with a conoid tail with a narrowly rounded tip, an arcuate infective female with a broadly rounded tail tip, and an almost straight to barely Jshaped male with angular (not heavily sclerotised) spicule and short bursa. Its status as a species is also supported by a combination of molecular analyses, its collection from several forms of small galls (see Discussion), association with a fergusoninid fly having larvae with a shield of the ‘plates with teeth’ form, host E. leucoxylon , and geographic distribution (collected only within the natural range of the host plant in SA).

Morphologically, it is similar to F. fisheri , F. gomphocephalae n. sp., F. microcarpae , F. porosae , and F. sporangae n. sp.

From phylogenetic analyses ( Ye et al. 2007) based on sequences of COI, F. leucoxylonae n. sp. is part of a clade of ‘pea gallers’, including F. sporangae n. sp. (V71) from E. leucoxylon and undescribed Fergusobia spp. from Eucalyptus sp. (V32).

The parthenogenetic female of F. leucoxylonae n. sp. (C-shaped) differs from F. camaldulensae , F. eugenioidae , F. fasciculosae , and F. sporangae n. sp. (arcuate to open C); and from F. leucadendrae , F. pohutukawa and F. rileyi (almost straight to arcuate). In length (170–383 µm), it is shorter than the parthenogenetic female of F. indica and F. magna (418–780 µm); and longer than that of F. cajuputiae (221–273 µm). The stylet (9–11.5 µm) of this parthenogenetic female is longer than in F. curriei (5–8 µm), F. floribundae (6–7 µm), F. juliae (5–7 µm), F. minimus (4–8 µm), and F. morrisae (7–8 µm). In having large to enormous pharyngeal glands (b’ 1.5–2.2), F. leucoxylonae n. sp. differs from F. pimpamensis and F. tumifaciens , which have smaller glands (respectively, b’ ranges are 4–9, 3–4, 4–5). It lacks the reflex or extra lobe found in the pharyngeal glands of F. quinquenerviae . In having a small, conoid tail that is arcuate, narrows gradually and has a bluntly rounded tip, the female differs from F. brevicauda , F. cajuputiae , F. camaldulensae , F. eugenioidae , F. fasciculosae , F. leucadendrae , F. nervosae , F. porosae , and F. viridiflorae which have more broadly rounded tips; from F. pohutukawa that has a straight, conoid tail; from F. dealbatae , F. floribundae , F. indica , F. magna , F. morrisae , F. pimpamensis , F. philippinensis , and F. ptychocarpae which have more slender, arcuate to straight tails; and from F. diversifoliae that has a body which narrows rapidly behind the vulva. The parthenogenetic female of F. leucoxylonae n. sp. is similar to that of F. gomphocephalae n. sp., F. microcarpae and F. jambophila , but can be separated from them by having a more narrowly rounded tail tip. It is also similar to F. fisheri , but its body shape tends to be more curved. It can be separated from F. colbrani , F. cosmophylla , F. delegatensae , F. brittenae , F. fisheri , F. tumifaciens and F. viminalisae by the position of the hemizonid (immediately in front of the secretory/ excretory pore vs 4–5, 5, 8–9, and 7–8 annules, respectively). Fergusobia leucoxylonae n. sp. also lacks the large secretory/excretory cell found in F. brittenae . Morphologically, it cannot be separated from F. schmidti n. sp.

The infective female of F. leucoxylonae n. sp. (arcuate with curved posterior regions) differs in shape from F. brittenae , F. curriei , F. dealbata , F. fasciculosae , F. nervosae , and F. philippinensis (open C-shape); and from F. camaldulensae , and F. rileyi (almost straight). In length (252–358 µm), it is smaller than the female of F. magna (537–633 µm), F. colbrani (369–405 µm), F. cosmophyllae (374–448 µm), F. curriei (417–489 µm), F. delegatensae (375–452 µm), F. juliae (396–550 µm), F. pimpamensis (369–443 µm), and F. ptychocarpae (387–471 µm); and tends to be smaller than F. tumifaciens (354–445 µm) and F. viminalisae (334–437 µm). The stylet of F. leucoxylonae n. sp. is longer than that of F. minimus (7–13 vs 4–5 µm). Their ratio a (7.3–12.6) is smaller than in F. magna (13.8–17.7), and larger than in F. cosmophyllae (4–6.8). In shape (arcuate, with a broadly rounded tip), the body posterior to the vulva differs from that of F. rileyi (more slender, straight, conoid), from F. eugenioidae , F. morrisae , F. ptychocarpae (more curved); and from F. porosae n. sp. (straight). The tail (11–18 µm) is shorter than in F. magna (78–132 µm), F. brevicauda (24–30 µm), F. brittenae (20–44 µm), F. camaldulensae (19–41 µm), F. dealbatae (22–27 µm), F. delegatensae (21–39 µm), F. diversifoliae n. sp. (23–39 µm), F. f i s h e r i (21–49 µm), F. floribundae (20–41 µm), F. juliae (26–44 µm), F. leucadendrae (23–30 µm), F. morrisae (19–32 µm), F. planchonianae (18–32 µm), F. philippinensis (20–28 µm), F. ptychocarpae (20–32 µm), F. quinquenerviae (20–29 µm), and F. rileyi (40–50 µm). The ratio c’ (0.5–1.2) is smaller than in F. magna (3.7–6.5), F. dealbatae (1.3–1.7), F. juliae (1.2–2.0), F. leucadendrae (1.5–1.6), and F. rileyi (2.2–3.1). Infective females of F. leucoxylonae n. sp. tend to have shorter tails than those of F. fasciculosae , F. gomphocephalae n. sp., F. microcarpae , F. porosae , and F. sporangae n. sp. Similarly, they tend to have shorter tails with more broadly rounded tips than those found in F. cajuputiae and F. viridiflorae . Morphologically, it cannot be separated from F. schmidti n. sp.

In shape (almost straight to barely J-shaped), the male of F. leucoxylonae n. sp. differs from males of F. magna , F. delegatensae , F. diversifoliae , F. fasciculosae , F. jul iae , and F. m or r i s a e, which have more strongly curved posteriors. In body length (251–293 µm), it is smaller than males of F. magna (446–588 µm), F. brevicauda (330–420 µm), F. brittenae (339–519 µm), F. camaldulensae (383–451 µm), F. cosmophyllae (374–502 µm), F. curriei (370–492 µm), F. dealbatae (314–432 µm), F. delegatensae (350–518 µm), F. diversifoliae (413–459 µm), F. eugenioidae (341–420 µm), F. floribundae (403–570 µm), F. juliae (377–453 µm), F. microcarpae (311–398 µm), F. minimus (368–502 µm), F. morrisae (347–413 µm), F. pimpamensis (407–525 µm), F. pohutukawa (398–469 µm), F. ptychocarpae (405–535 µm), F. rileyi (378–508 µm), and F. viridiflorae (329–418 µm). The male tail shape of F. leucoxylonae n. sp. (arcuate with a broadly rounded tip) differs from that of F. philippinensis (truncate tip); and from F. viridiflorae (slender, straight to arcuate). The male tail (20–30 µm) is shorter than in F. cajuputiae (35–50 µm), F. camaldulensae (33–54 µm), F. curriei (36–38 µm), F. dealbatae (32–50 µm), F. pimpamensis (41–57 µm), and F. pohutukawa (50–61 µm), and appears to be shorter than that of F. tumifaciens (40 µm). The spicule of F. leucoxylonae n. sp. (16–19 µm) is shorter than in F. brevicauda (21–27 µm), F. eugenioidae (23–25 µm), F. floribundae (20–23 µm), F. juliae (20–27 µm), F. schmidti (19–25 µm), and F. tumifaciens (18–22 µm); and larger than in F. cosmophyllae (12–15 µm), F. po ro s a e (11–15.5 µm), and F. vim inal isae (10–15 µm). In having an angular spicule, F. leucoxylonae n. sp. differs from F. jambophila , in which it is arcuate. The spicule of F. leucoxylonae n. sp. has an offset manubrium, differing from that of F. fisheri and F. sporangae n. sp., where it is not. The bursa of the male is short (arising 20–30% of the body length, anterior to the cloaca); differing from F. brevicauda , F. camaldulensae , F. c a j u pu t i a e, F. c o l b r a ni, F. delegatensae , F. diversifoliae , F. gomphocephalae n. sp., F. jambophila , F. leucadendrae , F. nervosae , F. pimpamensis , F. planchonianae , F. schmidti n. sp., F. pohutukawa , F. ptychocarpae , F. rileyi , F. viridiflorae , and F. viminalisae , in which it is greater than 30%. The male of F. leucoxylonae n. sp. lacks the reflexed pharyngeal gland found in F. quinquenerviae .

Remarks. Eighteen collections of small bud galls were made from E. leucoxylon . Of these, 16 were multilocular, and all bar one were sessile. The latter was stalked, and similar to the unilocular axial ‘pea’ galls from which F. sporangae n. sp. was collected. The galls were usually axial. Locules were usually discrete, and clustered in various ways, being scattered across leaf buds or along a petiole, or as an amorphous leaf gall. In the latter, locules could be formed within the gall, and not just on its surface.

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

Figures

FIGURE 4. Fergusobia schmidti n. sp. (all in lateral view): A, Entire parthenogenetic female; B, Head of parthenogenetic female; C, Habitus; D, Tails of parthenogenetic females; E, Entire infective female; F, Head of infective female; G, Habitus; H, Tails of infective females; I, Entire male; J, Head of male; K, Habitus; L, Tails of males. Scale bars: A, E, I = 50 µm. B, F, J = 5 µm. Tails not drawn to scale.

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

FIGURE 7. Spicules from Fergusobia spp. collected from small shoot bud galls: A, MSp 40 from E. marginata; B, F. rileyi; C, MSp 61 from E. delegatensis; D, MSp 55 from E. amygdalina; E, MSp 78 from E. blakelyi; F, MSp 59 from E. obliqua; G, MSp 41 from E. pauciflora; H, Fergusobia sp. from ABG from Eucalyptus sp. at Brisbane, QLD; I, MSp 30 from E. tereticornis; J, F. gomphocephalae n. sp.; K, F. leucoxylonae n. sp.; L, F. sporangae n. sp.; M, MSp 21 from E. microcarpae; N, Fergusobia sp. from E. odorata; O, MSp 28 from E.? siderophloia; P, MSp 39 from E. viminalis UABG form 2; Q, MSp 79 from E. fasciculosae; R, MSp 47 from E. cladocalyx; S, MSp 77 from E. confluens; T, Fergusobia sp. from LPG from Eucalyptus sp. at Indooroopilly, Brisbane, QLD; U, F. schmidti n. sp. Not drawn to scale.

Tables

TABLE 3. Measurements (µm) of Fergusobia leucoxylonae n. sp. from Eucalyptus leucoxylon. (mean ± standard deviation, with range in brackets).

	Holotype Partheno-genetic female	Parthenogenetic females	Males	Infective females
n	1	22	22	8
Length	300	285±4.7 (170 – 383)	276±13.1 (251 – 293)	281±36.4 (252 – 358)
a	9.3	8.4±1.4 (5.5 – 9.9)	10.8±0.8 (9.1 – 12.3)	10.3±1.7 (7.3 – 12.6)
b’	1.7	1.9±0.2 (1.5 – 2.2)	2.0±0.3 (1.5 – 2.5)	3.1±1.0 (2.4 – 5.0)
c	24.0	17.8±4.4 (11.4 – 30.6)	11.5±1.4 (8.8 – 14.7)	19.9±5.5 (12.4 – 28.6)
c’	1.0	1.3±0.3 (0.8 – 2.4)	1.5±0.3 (1.1 – 2.4)	0.8±0.3 (0.5 – 1.2)
V or T %	83.3	85.3±1.7 (81.8 – 87.3)	47.2±14.5 (22.1 – 76.9)	80.3±3.2 (75.2 – 83.3)
Body diameter	32	34±4.9 (25 – 43)	26±1.2 (23 – 29)	28±3.7 (21 – 32)
Stylet length	9	10±1.0 (9 – 11.5)	8±0.5 (7 – 9)	10±1.7 (7 – 13)
Ant. end to SE pore	79	73±17.8 (41 – 100)	74±8.9 (60 – 95)	68±8.2 (61 – 77)
Spicule length			18±1.2 (16 – 19)
Tail length	13	17±4.0 (13 – 30)	24±3.0 (20 – 30)	15±4.3 (11 – 18)