Fergusobia pauciflorae Davies, 2018

Davies, Kerrie A., Ye, Weimin, Taylor, Gary S., Scheffer, Sonja, Bartholomaeus, F. & Giblin-Davis, Robin M., 2018, Nematodes from galls on Myrtaceae. XI. Descriptions of five new species of Fergusobia from Australia, Zootaxa 4399 (1), pp. 1-31 : 16-20

Fergusobia pauciflorae Davies n. sp. apud MSp 73 ( Davies et al. 2012a)

( Fig. 4 )

Measurements. Table 5.

Material examined. Holotype: Parthenogenetic female, roadside King’s Highway, 10 km. east of Bungendore, New South Wales (35°25´S 149°45´E; 845 m above sea level). Taken from flower bud galls on Eucalyptus pauciflora Sieber ex Sprengel. Collected S. Scheffer , 6.vii.2004, Code 718. On a slide with a paratype infective female and a male, deposited in the ANIC, Canberra, ACT, Australia .

Paratypes. Vouchers (collection data as above) deposited at the WINC, The University of Adelaide, SA, Australia, 10 parthenogenetic ♀ s, 2 infective ♀ s and 8 Ƌs on slides numbered WINC 0 63798, ( WNC 2497 ) ; at the Australian Museum , Sydney, NSW, Australia, 4 parthenogenetic ♀ s, 1 infective ♀ s and 3 Ƌs on slides; and at the USDA Nematode Collection, Beltsville, MD, USA 1 parthenogenetic ♀ and 1 Ƌ on a slide. The description presented here is based on measurements of 21 parthenogenetic ♀ s, 12 infective ♀ s and 21 ♂ s.

Description. Parthenogenetic female. Body open C-shaped, with most curvature posterior to vulva; relatively small; relatively broad ( Fig. 4A ); smaller in size than infective females and males; body narrows behind vulva to form a narrow conoid tail. Cuticle not swollen when fixed, sub-cuticle with strong longitudinal striae. Lateral fields not seen.

Cephalic region ~ 80% diameter of body at anterior end, off-set, 2 µm high, unstriated; rounded outline in lateral view, circum-oral area may be slightly raised to form small rounded peak ( Fig. 4D ). Amphids not seen. Stylet strongly sclerotised, with cone ~40% of length, basal knobs just higher than wide, 2–3 µm wide at base, rounded.

Orifice of dorsal pharyngeal gland ~ 1 µm posterior to stylet knobs. Anterior fusiform part of digestive tract occupying 67 (49–75)% body diameter, length 2.8 (2.7–3.0) times diameter; lumen of tract broadens; lumen of tract broadens gradually at anterior end of dorsal pharyngeal gland. Pharyngeal glands enormous, extending over intestine, occupying 76 (74–82)% of body diameter, distance from head to posterior end of glands being 47 (36– 58)% of total body length. Gland nucleus large, with large nucleolus.

Secretory/excretory pore opens at approximate level of nucleus of pharyngeal gland; duct obscure. Hemizonid usually immediately anterior to excretory pore.

Reproductive tract extending part-way along pharyngeal gland or to nerve ring and occasionally anterior to it; flexed in 6/ 14 specimens examined; oviduct usually with two oocytes per row for a few rows posterior to cap cell, then one oocyte per row; quadricolumella with obvious clustered cells, not smooth; uterus long, not extensile, occasionally with an egg; vulva a simple transverse slit with flat lips; no vulval plate. Anus pore-like. Tail conoid, curving around ventral side; length 1.5–3 times anal body diameter; tip bluntly rounded ( Fig. 4G ).

Infective pre-parasitic female. Infects L3 larva or puparium of an undescribed species of Fergusonina . Open C-shape when relaxed by heat; with most curvature posterior to vulva, relatively broad; maximum body diameter at mid-body length; body tapers gradually posterior to vulva ( Fig. 4B ). Cuticle obscurely annulated, <1 µm wide; longitudinal striae apparent with light microscope; lateral fields not seen.

Cephalic region not offset; circum-oral area terminally flattened; rounded edges ( Fig. 4E ); stylet slender, weakly sclerotised with small basal knobs higher than wide; <2µm wide; cone ~ 40% of length.

Orifice of dorsal pharyngeal gland often obscure, ~1 µm posterior to stylet knobs. Anterior fusiform part of digestive tract little expanded, occupying 41–58% of body diameter, length 3.6 (2.7–4.5) times diameter. Pharyngeal glands relatively small, extending over intestine, occupying 59 (56–65)% body diameter, distance from head to posterior end of glands being 32 (26–38)% of total body length.

Position of secretory/excretory pore opening variable, from close to nerve ring to posterior to nucleus of pharyngeal glands; duct obscure. Hemizonid just anterior to pore.

Uterus packed with sperm in inseminated females; vagina at right angle to body axis; reproductive tract hypertrophied in some specimens. Vulva a transverse slit, vulval lips raised <1 µm, small vulval plate present. Anus an obscure pore. Tail broadly conoid; length 1–2.5 times diameter at anus, tip broadly rounded to almost hemispherical ( Fig. 4J ).

Male. Body straight to arcuate when relaxed by heat, tail region slightly curved ventrally ( Fig. 4C ). Cuticle weakly annulated, annules ~1µm wide; strong longitudinal striae apparent with light microscope; lateral fields not seen.

Cephalic region occupying 75–80% anterior body diameter, barely offset, ~ 2 µm high; circum-oral area flat or barely raised, with lightly sclerotised framework; stylet with cone ~40% of length, small round knobs <2 µm wide. Orifice of dorsal pharyngeal gland 1–2 µm behind knobs. Anterior fusiform part of digestive tract occupying 44–74% of body diameter, length 2.6 (2.3–2.8) times diameter. Pharyngeal glands extending over intestine, occupying 61 (50–71)% of body diameter, distance from head to posterior end of glands being 37 (28–54)% of total body length.

Secretory/excretory pore opens opposite nucleus of pharyngeal gland; secretory/excretory cell not seen. Hemizonid lens-like, extending over one or two annules, immediately or one or two annules in front of secretory/ excretory pore.

Reproductive tract with single testis, variable in length, usually extends to nerve ring but may extend anterior to it; occasionally flexed; testis, seminal vesicle and vas deferens not clearly differentiated in some specimens. Bursa leptoderan, reaching to tail tip, smooth; obscure; arises ~ 40–60% along length of body. Spicules paired, angular (90°) at ~ 40–50% of length, with manubrium and shaft usually longer than blade; moderately sclerotised; manubrium similar to or wider than shaft, may or may not be offset dorsally; blade narrows unevenly to bluntly rounded tip which may have concavity on distal edge; opening not seen ( Fig. 4M ). Inconspicuous muscles associated with cloaca. Tail arcuate, ventrally concave, conoid; length 1–2.5 times diameter at cloaca; broadly rounded tip ( Fig. 4L ).

Diagnosis and relationships. Fergusobia pauciflorae n. sp. is morphologically characterized by the combination of a medium sized, arcuate, parthenogenetic female with a small stylet, and a conoid tail with a bluntly rounded tip; a small, open C to J-shaped infective female with a broadly rounded to almost hemispherical tail tip; and a straight to arcuate male with a stout, angular spicule and bursa at ~70% of body length. Morphologically, F. pauciflorae n. sp. is similar to F. brittenae , F. fasciculosae , F. minimus , F. morrisae , F. planchonianae , F. pruinosae n. sp., F. ptychocarpae , F. robustae n. sp., and F. sporangae . It was collected from FBGs on E. pauciflora ( Eucalyptus , section Cineraceae), while the other nematodes named above were respectively collected from TLBGs, style galls, FBGs, ‘leafy’ LBGs, FBGs, FBGs, FBGs, and UABGs. All these FBGers and the TLBGers and UABGers came from host plants of the subgenus Symphyomyrtus , with F. ptychocarpae collected from Corymbia, i.e., from hosts that are clearly genetically different from that of F. pauciflorae n. sp. Only the host plant E. planchoniana is also from subgenus Eucalyptus . The third instar fly larvae associated with F. pauciflorae n. sp. had dorsal shields of the ‘bars of spicules’ form, differing from all but those with F. planchonianae . This non-morphological evidence supports the status of F. pauciflorae n. sp. as a true species. Morphologically, it differs from F. planchonianae in that the respective parthenogenetic females have differing shapes for the head capsule, and F. pauciflorae n. sp. has a longer tail (24 (14–32) vs 14 (11–16) µm). Infective females of F. pauciflorae n. sp. lack the post-anal sac of the intestine that is present in F. planchonianae . Males of F. pauciflorae n. sp. have a broader tail tip than F. planchonianae , and the form of the bursa differs, being smooth in the former but longer and with a crenate edge in the anterior part in the latter.

The parthenogenetic female of F. pauciflorae n. sp. (C-shape) differs from that of F. armillarisae , F. decorae and F. obliquae n. sp. (arcuate to open C-shaped); and from F. janetae n. sp., F. linariifolia and F. rileyi (straight or arcuate). In length (309–393 µm), the female is larger than that of F. decorae (205–302 µm), F. fasciculosae (237– 285 µm), F. fisheri (228–305 µm), F. leucadendrae (205–303 µm), F. nervosae (245–309 µm), F. rosettae (228–269 µm), and F. tumifaciens (224–307 µm); and smaller than F. indica (525–626 µm), F. magna (418–689 µm) and F. janetae n. sp. (514–723 µm). In having a non-extensile uterus, the female differs from F. armillarisae , F. brevicauda , F. camaldulensae , F. jambophila , F. linariifolia , F. magna , F. rileyi , and F. tolgaensis , in which it is extensile. In having cuticle which does not swell upon fixation; the parthenogenetic female of F. pauciflorae n. sp. differs from that of F. armillarisae , F. decorae , F. pohutukawa , and F. viridiflorae in which it does. Having a flat circum-oral area separates the parthenogenetic female of F. pauciflorae n. sp. and those of F. camaldulensae and F. jambophila , in which it is raised. The stylet (9–11 µm) is longer than in F. curriei (5–8 µm), F. floribundae (6–7 µm), F. juliae (5–7 µm), and F. minimus (4–8 µm), and tends to be larger than in F. philippinensis (7.5–9 µm) and F. pimpamensis (7–9 µm). In having large oesophageal glands, the parthenogenetic female of F. pauciflorae n. sp. is similar to that of F. quinquenerviae but lacks the extra lobe or flex found in glands of the latter. In having a body that narrows gradually behind the vulva, is curved and conoid in shape, with a bluntly rounded tail tip, the female differs from F. pohutukawa (straighter, with a narrowly rounded tip); F. indica , F. janetae n. sp., F. magna and F. rileyi (more slender, arcuate to straight); F. porosae (tail with smaller volume); F. leucoxylonae and F. obliquae (sub-triangular tail); F. brevicauda , F. cajuputiae , F. colbrani , F. curriei , F. fasciculosae , F. fisheri , F. gomphocephalae , F. juliae , F. leucadendrae , F. linariifolia , F. magna , F. microcarpae , F. quinquenerviae , F. rosettae , F. schmidti , F. sporangae , F. tumifaciens , F. viminalisae , and F. viridiflorae (broader, usually shorter tails); and F. planchonianae (with a shorter tail). The parthenogenetic female of F. pauciflorae n. sp. has the hemizonid opening immediately adjacent to the secretory/excretory pore or 2 annules anterior to it, separating it from F. brittenae , F. cosmophyllae , F. dealbatae , F. delegatensae , F. diversifoliae , and F. pruinosa (respectively, 8–9, 4–5, 4–6, 5, 8, and 5–6 annules anterior to the pore). The morphometrics of the parthenogenetic female of F. pauciflorae n. sp. overlap with those of F. eugenioidae , F. morrisae , F. pimpamensis , F. leucoxylonae , F. leptospermum , and F. robustae n. sp. The female can be separated from F. eugenioidae by the position of the secretory/excretory pore (80–105 vs 64–85 µm posterior to the anterior end in the latter); from F. morrisae by the shape of the cephalic capsule (flat vs peaked); from F. robustae n. sp. by the form of the vulval lips (flat vs raised); and from F. leptospermum in intestinal structure (lacking vs with a clear lining); and from F. pimpamensis by body diameter (31 (25–36 µm) vs 41 (36–46 µm)). Morphologically, it is not possible to separate this stage from that of F. ptychocarpae .

The body of the infective female of F. pauciflorae n. sp. (open C to J) differs in shape from that of F. armillarisae , F. camaldulensae , F. colbrani . F. cosmophyllae , F. dealbatae , F. decorae , F. diversifoliae , F. fasciculosae , F. gomphocephalae , F. leucadendrae , F. linariifolia , F. nervosae , F. obliquae n. sp., F. pimpamensis , F. philippinensis , F. sporangae , F. tolgaensis , and F. viminalisae (straight to arcuate). In length (309–393 µm), the infective female is smaller than that of F. curriei , F. eugenioidae , F. janetae n. sp., F. juliae , F. magna , and F. minimus ; tends to be smaller than that of F. brittenae (375–550 µm), F. cosmophyllae (374–448 µm), and F. ptychocarpae (387–471 µm); and is larger than that of F. armillarisae (279–291 µm), F. cajuputiae (239–309 µm), F. decorae (207–256 µm), F. gomphocephalae (222–291 µm), F. leucadendrae (227–291 µm), F. nervosae (282 µm), F. quinquenerviae (259–325 µm), F. porosae (277–300 µm), and F. tolgaensis (223–272 µm). The stylet (8– 10 µm) is longer than in F. colbrani (8.5 µm) and F. minimus (4–5.5 µm), and smaller than that of F. leptospermum (11 µm). The infective female has a shorter tail (20–32 µm) than that of F. janetae n. sp. (91 µm), F. leptospermum (34–38 µm), F. magna (78–131 µm) and F. rileyi (40–50 µm). The female has a sub-cylindroid tail with a broadly rounded tip, separating them from the infective female of F. porosae (tail tip bluntly rounded); from F. gomphocephalae and F. pruinosae n. sp. (notched tip); from F. philippinensis (truncate tip); and from F. curriei , F. delegatensis , F. fisheri , F. floribundae , F. leucoxylonae , F. microcarpae , F. planchonianae , F. robustae n. sp., F. rosettae , F. schmidti , and F. pimpamensis (broad, hemispherical tip). The sub-cylindroid tail form also separates the infective female of F. pauciflorae n. sp. from that of F. brevicauda and F. viridiflorae (tail more cylindroid), and from F. tumifaciens which has a relatively broader tail (c’ 1.2–2.3 vs 0.7–1.2 in F. tumifaciens ). Infective females of F. pauciflorae n. sp. and F. morrisae cannot be separated morphologically.

In shape (straight to arcuate), the male of F. pauciflorae n. sp. differs from that of F. brittenae , F. curriei , and F. fasciculosae (J-shape), F. pimpamensis (J or C-shape), F. diversifoliae , F. juliae , F. magna , F. planchonianae , F. ptychocarpae , and F. viridiflorae (with strongly curved posterior). In having a flat circum-oral area, the male is separated from that of F. camaldulensae , F. jambophila , and F. tolgaensis , in which it is raised. The length of the tail in the male of F. pauciflorae n. sp. (23–46 µm) is shorter than in F. janetae n. sp. (82–111 µm), F. magna (54– 87 µm), F. pohutukawa (50–61 µm), and F. rileyi (58–70 µm), and tends to be shorter than that of F. leptospermum (43–57 µm). The shape of the tail (arcuate with a broadly rounded tip) differs from that of F. philippinensis (truncate tip), F. rileyi (slender, straight, with bluntly rounded tip) and from F. leucadendrae (bluntly rounded tip). In having an angular spicule, F. pauciflorae n. sp. differs from F. armillarisae and F. rosettae , in which it is arcuate. The spicule is stout in form, differing from those in F. obliquae n. sp., F. pruinosae n. sp., and F. janetae n. sp., in which they are slimmer. In F. pauciflorae n. sp., the manubrium of the spicule is not offset, but it is offset in F. cajuputiae . In the male of F. pauciflorae n. sp., the bursa arises at ~ 70% of body length, separating it from that of F. brevicauda , F. colbrani , F. cosmophyllae , F. dealbatae , F. decorae , F. eugenioidae , F. fisheri , F. floribundae , F. gomphocephalae , F. jambophila , F. juliae , F. microcarpa , F. minimus , F. nervosae , F. schmidti , F. porosae , F. quinquenerviae , F. robustae n. sp., F. rosettae , F. schmidti , F. sporangae , F. tolgaensis , F. tumifaciens , and F. viminalisae , in which the bursa is shorter; and F. janetae n. sp., F. leptospermum , F. linariifoliae , F. pohutukawa , F. rileyi , and F. viridiflorae in which it is longer. The bursa of F. pauciflorae n. sp. is smooth, but it is crenate in F. delegatensae . Morphometrically, males of F. pauciflorae n. sp. and F. morrisae overlap, but in F. pauciflorae n. sp. the secretory/excretory pore does not open onto an area of raised cuticle as in F. morrisae .

Etymology. Named after Eucalyptus pauciflora , the plant species from which the nematodes were collected.

Figures

FIGURE 4. Fergusobia pauciflorae n. sp. ex E. pauciflora (all in lateral view): A, Entire parthenogenetic female; B, Entire infective female; C, Entire male; D, Anterior end of parthenogenetic female; E, Anterior end of infective female; F, Anterior end of male; G; Tails of parthenogenetic females; H, Habitus of parthenogenetic females; I, Habitus of infective females; J, Tails of infective females; K, Habitus of males; L, Tails of males; M, Spicules. Scale bars: A, B, C = 50 µm; D, E, F = 10 µm; G, J, L = 25 µm; M = 5 µm.