Fergusobia gomphocephalae 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 : 5-10

Description of Fergusobia gomphocephalae Davies n. sp.

( Figs 2 , 3 , 7 I, 8J)

= Fergusobia MSp . 9 apud Davies et al. 2010 a

Measurements. Table 2 .

Material examined. The description presented here is based on measurements of 21 parthenogenetic ♀s, 9 pre-parasitic infective ♀s, and 16 ♂ s. From Cervantes Caravan Park, Cervantes, 250 km north of Perth, WA, Australia (30°31´S 115°05´E), and Tuart Reserve, Cervantes, WA, Australia (30°25´S 115°08´E). Taken from unilocular bud galls on Eucalyptus gomphocephala associated with Fergusonina newmani Tonnoir 1937 . Collected by K.A. Davies, 24.x.2000.

Holotype. Parthenogenetic female on a slide deposited in the ANIC, Canberra, ACT, Australia, collected at Cervantes Caravan Park, Cervantes, Western Australia, together with one infective female and one male; collection data as above.

Paratypes. Nine parthenogenetic ♀s, 3 pre-parasitic infective ♀s, 6 ♂ s were deposited at the WINC, The University of Adelaide, SA, Australia, 10 parthenogenetic ♀s, 5 pre-parasitic infective ♀s, 8 ♂ s at Western Australian Museum, Perth, WA, Australia, and 1 parthenogenetic ♀, 1 pre-parasitic infective ♀, and 1 ♂ at the USDA Nematode Collection, Beltsville, MD, USA. Collection data as above.

Holotype Parthenogenetic females Males Infective females

Partheno-genetic

female

Description. Parthenogenetic female. From unilocular ‘pea’ galls on young leaves and stems on E. gomphocephala . When heat relaxed, body usually dorsally curved with ventral side convex to form a C-shape, with greatest curvature behind the vulva; body narrows sharply behind vulva to form conoid tail, with most narrowing on ventral side; similar in size to pre-parasitic infective female and to male. With light microscope, cuticle has obscure annuli, and longitudinal striae are apparently present. Using SEM, cuticle is clearly annulated (~ 1µm wide), no longitudinal striae. While not seen with the light microscope, with SEM lateral fields arise ~20 µm behind anterior end, ~2 µm wide at mid-body, contain many clear, diagonal striae; which change at level of vulva to become less defined and irregular and continue almost to tail tip.

Cephalic region 70% diameter of body at anterior end, offset, 1–2 µm high, unstriated; in lateral view has rounded outline and circum-oral area flat or slightly raised. With SEM, 4 distinct, respectively alternating with 4 indistinct, sectors are apparent. Six small cephalic papillae can be seen on the circum-oral area, surrounding the stylet opening. Amphid openings rounded, pore-like and closer to the edge of the sectors than the circum-oral area. Stylet 7–9 µm long, with conus 40–50% of length, basal knobs 1–2 µm wide at base, small, round.

Orifice of dorsal pharyngeal gland 1–2 µm posterior to stylet knobs. Anterior fusiform part of digestive tract occupying 53–73% of body diameter, length 1.8–2.5 times diameter; lumen of tract broadening behind dorsal pharyngeal gland. Pharyngeal glands extending over intestine, large, diameter 61–78% of body diameter, distance from head to end of glands being 53 (31–67)% of total body length.

Secretory/excretory pore opens 72–93 µm from anterior end with prominent duct opening onto area of slightly raised cuticle, at about 20% length of pharyngeal gland; secretory/excretory cell not seen. Hemizonid extending over one annulus, 1 annulus anterior to secretory/excretory pore.

Reproductive tract comprising ovary with growth zone occupying ~ 60% of length, oviduct comprising two or three rows of cells with structure unclear, no spermatheca, quadricolumella present, not smooth, uterine sac about one vulval body width in length. Tract variable in length, extending part-way along dorsal pharyngeal gland; not flexed but with cap cell usually offset from growth zone; latter with one or two oocytes per row; uterine sac containing no eggs or one (in 2 of 22 specimens examined) egg; vulva with protruding lips in some specimens, flat or a depressed slit in others. Tail conoid, may be concave on dorsal side, length 1–2 times anal body diameter, with a rounded tip.

Infective pre-parasitic female. From unilocular ‘pea’ galls on young leaves and stems on E. gomphocephala . Penetrates mature larval stage of Fn. newmani or pupa. Body J or C-shaped when relaxed by heat, with greatest curvature behind vulva; maximum body diameter at mid-body in some and at vulva in others; cuticle with obscure annulations and longitudinal striae; lateral fields not seen.

Cephalic region barely or not offset; circum-oral area flat or slightly raised; stylet slender, 6–10 µm long, weakly sclerotised with round basal knobsbeing slightly higher than wide, 1–2 µm in width; conus 50% of total stylet length.

Orifice of dorsal pharyngeal gland barely posterior to stylet knobs. Anterior fusiform part of digestive tract occupying 48–64% of body diameter, 2.4–3.5 times diameter in length. Pharyngeal glands extending over intestine, 31–50% of body diameter in diameter, distance from head to end of glands being 30 (28–37)% of total body length.

Secretory/excretory pore opens 59–83 µm behind anterior end, opposite pharyngeal gland nucleus; prominent duct opens onto area of slightly raised cuticle; secretory/excretory cell not seen. Hemizonid extending over one annule, 1 annule anterior to secretory/excretory pore.

Uterus 80% of total gonad length in uninseminated female, packed with amoeboid sperms in inseminated female; vagina at right angle to body axis, plugged with refractive material; reproductive tract extending alongside dorsal pharyngeal gland; hypertrophy of tract in some specimens. Vulval lips flat or barely raised. Tail short, broad, in length 0.6–1.3 times diameter at anus, tip almost hemispherical and may be notched.

Male. From unilocular ‘pea’ galls on young leaves and stems on E. gomphocephala . Body arcuate to J-shaped when relaxed by heat, tail region more or less curved ventrally. Cuticle with obscure annuli ~1 µm wide, longitudinal striations not seen; lateral fields not seen.

Cephalic region offset, 1–2 µm high; circum-oral area flat or raised, with lightly sclerotised framework; stylet 7–10 µm long, with conus 50% of length, round stylet knobs with ~ 2 µm width. Anterior fusiform part of digestive tract occupying 51–75% of body diameter, 2.6–3.2 times diameter in length. Pharyngeal glands extending over intestine, occupying 50–70% of body diameter, distance from head to end of glands being 33–59% (mean 48%) of total body length; gland nucleus may be positioned at anterior or posterior end of gland. Lumen of intestinal tract broadens at posterior end or behind pharyngeal glands.

Secretory/excretory pore opens 59–93 µm behind anterior end, at ~ 30–40% of length of pharyngeal gland and in front of gland nucleus; prominent duct opens onto area of slightly raised cuticle in some specimens; secretory/ excretory cell not seen. Hemizonid extending over two annuli, barely anterior to secretory/excretory pore.

Reproductive tract with single testis, variable in length, may extend to base of pharyngeal glands, or to secretory/excretory pore, but usually overlaps dorsal pharyngeal gland; may be reflexed; testis, seminal vesicle and vas deferens not clearly differentiated. Bursa membranous, smooth or crenate, peloderan; may be prominent or obscure; arises 30 – 50% along length of body. Spicules paired, angular near their middle, small but robust; moderately sclerotised; manubrium offset in some specimens, similar to or slightly wider than shaft; blade narrows gradually with notch on proximal side similar to the tip; opening terminal. Inconspicuous muscles associated with cloaca. Tail ventrally concave, curved; in length 1.1–2.6 times diameter at cloaca, tip bluntly rounded.

Molecular phylogenetic relationships. For molecular analysis, the D2/D3 expansion segments of LSU ( AY589352 ) and mtCOI ( AY589435 ) of V63 ( F. gomphocephalae n. sp.) were sequenced. Based on the combined data from D2/D3 and mtCOI, V63 is in a monophyletic clade with V4 ( F. juliae from FBG on E. macrorrhyncha ), V32 (MSp 28 from Eucalyptus sp.), V65 ( F. fasciculosae from stylet galls on E. fasciculosa ) and V71 ( F. leucoxylonae n. sp.) ( Ye et al. 2007, Fig. 5 ). The blastn search of LSU (853 bp sequenced) on V63 revealed it has 6–12-bp differences (99% identity) and 2–4 gaps with V32 ( AY589328 ), V65 ( AY589354 ), V68 ( AY589357 ), V71 ( AY589360 ) and V314 ( FJ386989 ). The blastn search of mtCOI (618 bp sequenced) on V63 revealed it has 37–45- bp differences (93–94% identity) with V4 ( AY589406 ), V65 ( AY589437 ), V69 ( AY589440 ) and V741 ( EF 011098 ) ( F. leucoxylonae n. sp.). These large sequence divergences support F. gomphocephalae n. sp. as a unique species.

Diagnosis and relationships. Fergusobia gomphocephalae n. sp. (MSp 9 in Davies et al. 2010a) is morphologically characterized by the combination of a small C-shaped parthenogenetic female with a variable, conoid tail, a small C-shaped infective female with a hemispherical tail tip, and an arcuate or J-shaped male with broad tail, angular spicule and short peloderan bursa. Its status as a species is also supported by a combination of molecular analyses, gall form, association with Fergusonina (Fn.) newmani , host E. gomphocephala , and geographic distribution (collected only within the natural range of the host plant in WA).

All stages are morphologically similar to those of F. leucoxylonae n. sp., F. sporangae n. sp., F. microcarpae Davies 2013 (in Davies et al. 2013a) and F. porosae Davies 2013 (in Davies et al. 2013a). In addition, parthenogenetic and infective females are similar to those of F. fisheri Davies & Lloyd 1996 .

From phylogenetic analyses based on sequences of D2/D3 and mtCOI, F. gomphocephalae n. sp. is genetically close to Fergusobia spp. from pea galls and flower bud galls on E. microcarpa , F. fasciculosae Davies 2012 (in Davies et al. 2012b) from stylet galls on E. fasciculosa , and F. juliae Davies 2012 (in Davies et al. 2012b) from flower bud galls on E. macrorhyncha .

In body shape (C-shaped), the parthenogenetic female of F. gomphocephalae n. sp. differs from F. camaldulensae Davies 2012 (in Davies et al. 2012a) and F. sporangae n. sp. (arcuate); and F. rileyi Davies 2012 (in Davies et al. 2012a) (almost straight). In body length (239–331 µm), F. gomphocephalae n. sp. is shorter than F. brittenae (328–461 µm) Davies 2010 (in Taylor & Davies 2010), F. cosmophyllae Davies 2013 (in Davies et al. 2013b) (354–406 µm), F. delegatensae Davies 2013 (in Davies et al. 2013b) (345–527 µm), F. eugenioidae Davies 2012 (in Davies et al. 2012b) (298–354 µm), F. magna Siddiqi 1986 sensu Davies 2010 (in Davies et al. 2010b) (500–780 µm), and F. i n di ca ( Jairajpuri 1962) Siddiqi 1986 (525–626 µm). The stylet (7–9 µm) of the parthenogenetic female is shorter than that in F. camaldulensae (11–13 µm), F. indica (12–15 µm), F. microcarpae (9.5–11 µm), F. pohutukawa Davies 2007 (in Taylor et al. 2007) (10–11 µm), F. rileyi (10–13 µm) and F. sporangae n. sp. (12–14 µm); and tends to be shorter than in F. planchonianae Davies 2013 (in Davies et al. 2013b) (9–12 µm), F. tumifaciens ( Currie 1937) Wachek 1955 sensu Davies 2014 (in Davies et al. 2014b) (9–11 µm), and F. viminalisae Davies 2014 (in Davies et al. 2014b) (9–10 µm). In having large to enormous pharyngeal glands (b’ 1.5–3.2), it differs from F. jambophila Siddiqi 1986 , and F. philippinensis Siddiqi 1994 which have smaller glands; and from F. quinquenerviae Davies & Giblin-Davis 2004 which has glands that are reflexed or have an extra lobe. The shape (conoid, with tail with straight sides and bluntly rounded tip) of the body behind the vulva in F. gomphocephalae n. sp. differs from that of F. dealbatae Davies & Giblin-Davis 2004 (more slender); F. diversifoliae Davies 2013 (in Davies et al. 2013b) (narrows more rapidly); F. curriei Fisher & Nickle 1968 , F. fisheri (narrows more gradually); F. pohutukawa (conoid, straight); F. floribundae Davies 2013 (in Davies et al. 2013b), F. juliae , F. morrisae Davies 2012 (in Davies et al. 2012b), F. pimpamensis Davies 2013 (in Davies et al. 2013b), F. porosae , F. planchonianae Davies 2014 (in Davies et al. 2014b) and F. ptychocarpae Davies 2008 ( Taylor & Davies 2008) (more slender); F. brevicauda Siddiqi 1994 , F. cajuputiae Davies & Giblin-Davis 2004 , F. camaldulensae , F. fasciculosae , F. leucadendrae Davies & Giblin-Davis 2004 , F. nervosae Davies & Giblin-Davis 2004 and F. viridiflorae Davies & Giblin-Davis 2004 (tips more broadly rounded). The parthenogenetic female of F. gomphocephalae n. sp. tends to have a smaller stylet than that of F. leucoxylonae n. sp. and F. planchonianae (respectively, 7–9 µm vs 9–11.5 µm and 9–12 µm). It is difficult to separate the parthenogenetic female of F. gomphocephalae n. sp. and F. minimus Lisnawita 2013 (in Davies et al. 2013b) but the latter tends to be larger, to be more tightly coiled when heat relaxed, and to have the body behind the vulva forming a more elongate conoid shape. Morphologically, the parthenogenetic female of F. gomphocephalae n. sp. cannot be separated from that of F. schmidti n. sp. and F. colbrani Davies 2014 (in Davies et al. 2014a).

The infective female (body an open C-shape with strongly curved posterior region) of F. gomphocephalae n.

sp. differs in shape from those of F. cajuputiae , F. camaldulensae , F. colbrani , F. cosmophyllae , F. dealbatae , F. delegatensisae , F. diversifoliae , F. fasciculosae , F. floribundae , F. leucadendrae , F. leucoxylonae , F. m a gn a, F. nervosae , F. pimpamensis , F. philippinensis , F. porosae , F. quinquenerviae , and F. viridiflorae (arcuate to open C); from F. eugenioidae , F. juliae , F. morrisae , and F ptychocarpae (strongly curved in posterior region); and from F. rileyi (almost straight). In length (222–298 µm), the female is smaller than F. magna (537–633 µm), F. brevicauda (330–410 µm), F. brittenae (375–550 µm), F. camaldulensae (346–454 µm), F. colbrani (369–405 µm), F. cosmophyllae (374–448 µm), F. curriei (417–489 µm), F. delegatensae (375–452 µm), F. diversifoliae (357–473 µm), F. eugenioidae (438 µm), F. juliae (396–550 µm), F. minimus (419–458 µm), F. morrisae (322–395 µm), F. pimpamensis (369–443 µm), F. planchonianae (303–339 µm), F. ptychocarpae (387–471 µm), F. rileyi (378–432 µm), F. tumifaciens (345–445 µm), and F. vim inal isae (334–437 µm). The shape of the tail tip (hemispherical) differs from that of F. microcarpae (broadly rounded). The infective female of F. gomphocephalae n. sp. tends to be smaller than those of F. f i s he r i (mean 272 µm, 222–298 µm vs mean 349 µm, 241–395 µm). There is a tendency for the vulva to be more anterior in F. gomphocephalae n. sp. than in F. sporangae n. sp. (mean 77%, 73–81% vs mean 83%, 80–88%). Morphologically, the infective female of F. gomphocephalae n. sp. cannot be separated from that of F. schmidti n. sp.

In shape (arcuate to J-shaped), the male of F. gomphocephalae n. sp. differs from those of F. jambophila (almost straight). Length (228–283 µm) is shorter than in F. magna (446–588 µm), F. brevicauda (330–420 µm), F. camaldulensae (383–451 µm), F. c o l b r a ni (288–481 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. fisheri (292–453 µm), F. floribundae (403–570 µm), F. juliae (377–453 µm), F. minimus (368–502 µm), F. morrisae (347–413 µm), F. pimpamensis (407–525 µm), F. philippinensis (280–390 µm), F. pohutukawa (398–469 µm), F. planchonianae (291–373 µm), F. ptychocarpae (405–535 µm), F. r i l e yi (378–508 µm), F. sporangae n. sp. (292–400 µm), F. tumifaciens (314–481 µm), F. viminalisae (337–463 µm), and F. viridiflorae (329–418 µm). In F. gomphocephalae n. sp., the ratio ‘ a ’ (7.6–11.3) is smaller than in F. pohutukawa (12.2–15.5). The male of F. gomphocephalae n. sp. lacks the reflex or additional lobe of the pharyngeal gland that is seen in F. quinquenerviae . The tail shape (arcuate with a bluntly rounded tip) of the male of F. gomphocephalae n. sp. differs from that of F. magna and F. viridiflorae (arcuate, more slender); and F. philippinensis (truncate tip). Tail (20–33 µm) is shorter than in F. cajuputiae (35–50 µm), F. pimpamensis (41–57 µm), and F. pohutukawa (50–61 µm). Spicule (14–18 µm) in F. gomphocephalae n. sp. is smaller than in F. brevicauda (21–27 µm), F. brittenae (19–25 µm), F. eugenioidae (23–25 µm), F. juliae (20–27 µm), F. philippinensis (19–23 µm), F. pohutukawa (19–24 µm), F. ptychocarpae (19–21 µm), F. rileyi (19–23 µm), and F. tumifaciens (18–22 µm). In having an angular shape, the spicule differs from that of F. jambophila , where it is arcuate. The spicule of F. gomphocephalae n. sp. is more heavily sclerotised than in F. fasciculosae , F. leucadendrae , F. leucoxylonae n. sp., F. microcarpae , F. nervosa , and F. s c h m i d t i n. sp. The angle near mid-length of the spicule is smaller in F. gomphocephalae n. sp. than in F. schmidti n. sp. Fergusobia gomphocephalae n. sp. has a short bursa arising at 30–50% of body length, differing from F. cajuputiae (50–70%). It can be separated from F. p oro s a e by the position of the hemizonid, immediately in front of the secretory/excretory pore in F. gomphocephalae n. sp. vs 4–5 annules in front in F. p oro s a e.

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

Figures

FIGURE 2. SEM of E. gomphocephalae n. sp.: A, Head; B, Lateral line and vulva; C, tail showing lateral line extending almost to tip. Scale bars = 5 µm. Arrow indicates amphid opening.

FIGURE 3. Fergusobia leucoxylonae 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 2. Measurements (µm) of Fergusobia gomphocephalae n. sp. from Eucalyptus gomphocephala. (Mean ± standard deviation, with range in brackets).

n	1	21	16	9
Length	312	291±23.7 (239 – 331)	264±19.9 (228 – 283)	272±24.3 (222 – 298)
a	8.9	8.4±0.5 (7.5 – 9.4)	9.5±1.0 (7.6 – 11.3)	9.4±0.7 (8.6 – 10.7)
b’	1.8	1.9±0.4 (1.5 – 3.2)	2.1±0.4 (1.7 – 2.6)	3.2±0.3 (2.7 – 3.5)
c	13.5	16.3±3.1 (11.6 – 23.6)	11.0±1.5 (9.1 – 13.1)	14.1±4.7 (7.6 – 19.9)
c’	1.4	1.4±0.3 (1.0 – 2.0)	1.5±0.4 (1.1 – 2.6)	1.0±0.3 (0.6 – 1.3)
V or T %	84.0	86.3±2.4 (81.2 – 90.9)	41.8±13.5 (17.8 – 62.5)	77.4±2.3 (73.1 – 80.6)