Fergusobia obliquae 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 : 21-25

Fergusobia obliquae Davies n. sp. apud MSp 59 ( Davies et al. 2012a)

( Fig. 5 )

Measurements. Table 6.

Material examined. Holotype: Parthenogenetic female, Deep Creek Conservation Park (35°61´S 138°26´E). Unilocular galls on the blades of leaves of Eucalyptus obliqua L’Hérit. , collected K.A. Davies, 18.ix.2001 . 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, 3 infective ♀ s and 18 Ƌs on slides numbered WINC 0 26080 ( WNC 2230); and at the USDA Nematode Collection, Beltsville, MD, USA 1 parthenogenetic ♀ and 1 Ƌ on a slide. Fifteen parthenogenetic ♀ s, 4 pre-parasitic infective ♀ s and 20 ♂ s examined.

Description. Parthenogenetic female. Body shape arcuate; relatively small; relatively broad (semi-obese); maximum diameter at mid-body; tend to be smaller than infective females and smaller than males; body narrows behind vulva to form a small conoid tail. Cuticle annulations weak, sub-cuticle with strong longitudinal striae. Lateral fields not seen.

Cephalic region ~ 64–82% diameter of body at anterior end, off-set, 1.5–4 µm high, unstriated; rounded outline in lateral view, circum-oral area flat. Amphids not seen. Stylet strongly sclerotised, with cone 58–67% of length, basal knobs just higher than wide, ~2 µm wide at base, rounded.

Orifice of dorsal pharyngeal gland ~ 1 µm posterior to stylet knobs. Anterior fusiform part of digestive tract occupying 70–80% body diameter, length 1.8–1.9 times diameter; lumen of tract broadens at distal end of dorsal pharyngeal gland. Pharyngeal glands enormous, extending over intestine, occupying 80 (67–91)% of body diameter, distance from head to posterior end of glands being 51 (40–58)% of total body length. Gland nucleus large, with large nucleolus. Lumen of intestinal tract broadens gradually at about half length of pharyngeal gland.

Secretory/excretory pore opens anterior to or at level of nucleus of pharyngeal gland; duct obscure; secretory/ excretory cell not seen. Hemizonid not seen.

Reproductive tract extending to nerve ring; flexed up to four times in some specimens; oviduct usually with one oocyte per row; quadricolumella with obvious clustered cells, not smooth; uterus not extensile, usually with one egg; vulva a simple transverse slit with flat lips; no vulval plate. Anus pore-like. Tail small, conoid, convex ventrally; length 1–2.5 times anal body diameter; tip broadly rounded.

Infective pre-parasitic female, infects third stage larva of unknown species of Fergusonina . Arcuate when relaxed by heat; maximum body diameter at mid-body length; body tapers gradually in tail region. Cuticle obscurely annulated, <1 µm wide; longitudinal striae apparent with light microscope; lateral fields not seen.

Cephalic region offset; circum-oral area flat; stylet slender, weakly sclerotised with small basal knobs higher than wide; <2µm wide; cone ~ 50–57% of length.

Orifice of dorsal pharyngeal gland often obscure, ~1 µm posterior to stylet knobs. Anterior fusiform part of digestive tract expanded, occupying 69–79% of body diameter. Pharyngeal glands extending over intestine, occupying 58 (51–69)% body diameter, distance from head to posterior end of glands being 29–33% of total body length.

Secretory/excretory pore opens at level of pharyngeal gland nucleus; duct obscure. Hemizonid obscure, 1 or 2 annules in front of pore.

Uterus packed with sperm in inseminated females; vagina perpendicular to body axis; reproductive tract hypertrophied in some specimens. Vulva a transverse slit, vulval lips flat, no vulval plate present. Anus an obscure pore. Tail cylindroid; length ~ 1.5 times diameter at anus, tip almost hemispherical.

Male. Body C-shaped when relaxed by heat, tail region slightly concave ventrally. Cuticle clearly annulated, annules ~1µm wide; strong longitudinal striae in sub-cuticle apparent with light microscope; lateral fields not seen.

Cephalic region occupying 79–85% anterior body diameter, offset, 2–3 µm high; circum-oral area flat or barely raised, with lightly sclerotised framework; stylet long, with cone 50–58% of length, small round stylet knobs <2 µm wide.

Orifice of dorsal pharyngeal gland ~ 1 µm behind knobs. Anterior fusiform part of digestive tract occupying 42–69% of body diameter, length 2.5 (2.3–3.0) times diameter. Pharyngeal glands extending over intestine, occupying 80 (72–89)% of body diameter, distance from head to posterior end of glands being 37 (35–46)% of total body length.

Secretory/excretory pore opens opposite nucleus of pharyngeal gland; duct obscure; secretory/excretory cell not seen. Hemizonid lens-like, extending over two annules, 2 annules in front of secretory/excretory pore.

Reproductive tract with single outstretched testis, variable in length, extends part way along gland or to nerve ring; usually outstretched but may be flexed; testis, seminal vesicle and vas deferens not clearly differentiated.

Bursa peloderan (but usually appears to be leptoderan), smooth; may be prominent or obscure; arises ~ 50–80% along length of body. Spicules paired, angular at ~ 40–50% of length, with manubrium and shaft longer than blade; moderately sclerotised; manubrium similar to or wider than shaft, offset dorsally; blade narrows unevenly to bluntly rounded tip with concavity on distal edge; opening sub-terminal. Inconspicuous muscles associated with cloaca. Tail arcuate, ventrally concave, conoid; length 2–2.5 times diameter at cloaca; bluntly rounded tip.

Diagnosis and relationships. Fergusobia obliquae n. sp. is morphologically characterized by the combination of a relatively broad, arcuate parthenogenetic female having a small but strongly sclerotised stylet, and a short conoid tail with a bluntly rounded tip; an arcuate infective female with an almost hemispherical tail tip; and a Cshaped male with an arcuate to angular spicule which is not heavily sclerotised and bursa arising 50–80% of body length. Morphologically, F. obliquae n. sp. is similar to F. robustae n. sp., F. pruinosae n. sp., and F. morrisae . It was collected from unilocular LPGs from the host plant E. obliqua (subgenus Eucalyptus , section Eucalyptus ), and its associated third instar fly larva lacks a dorsal shield. The species with morphological similarity are from host plants of the subgenus Symphyomyrtus , and were collected from TLBGs or FBGs. Nothing is known of the shield form of the third instar larvae associated with F. pruinosae n. sp., but the fly larva associated with F. robustae n. sp. and F. morrisae had shields with teeth. While DNA sequences are not available for F. obliquae n. sp., the data on host plant associations, gall forms and shield forms of morphologically similar Fergusobia species supports its status as a distinct species.

The parthenogenetic female of F. obliquae n. sp. (arcuate shape) differs from that of F. brevicauda , F. brittenae , F. cosmophyllae , F. diversifoliae , F. fasciculosae , F. floribundae , F. gomphocephalae , F. indica , F. leucoxylonae , F. magna , F. microcarpae , F. minimus , F. morrisae , F. pimpamensis , F. planchonianae , F. porosae , F. ptychocarpae , F. schmidti , F. tumifaciens , F. viminalisae , and F. viridiflorae (C-shape). In size (length 294–370 µm), the female of F. obliquae n. sp. is smaller than that of F. indica (525–626 µm), F. janetae n. sp. (514–723 µm) and F. magna (418–689 µm); and larger than that of F. cajuputiae (221–273 µm), F. fasciculosae (237–285 µm) and F. rosettae (228–269 µm). The female tends to be larger than F. leucadendrae (L = 205–303 µm) and F. tumifaciens (L = 224–307 µm). Having a flat circum-oral area separates the parthenogenetic female of F. obliquae n. sp. and those of F. camaldulensae , F. eugenioidae , F. jambophila , and F. tolgaensae , in which it is raised. In addition, the cephalic region is like a flattened dome in the female of F. obliquae n. sp., but in F. dealbatae and F. pruinosae it has straight sides. The stylet (10–12 µm) of the parthenogenetic female is longer than in that of F. curriei (5–8 µm), F. juliae (5–7 µm) and F. minimus (4–8 µm). In having enormous oesophageal glands, the parthenogenetic female of F. obliquae n. sp. is similar to the female of F. quinquenerviae but lacks the extra lobe or flex found in glands of the latter. In having a body that narrows sharply behind the vulva to form a small conoid tail with a broadly rounded tip, the parthenogenetic female is similar to that of F. fisheri , but tends to differ in tail length (20 (15–33) vs 14 (13–16) µm in F. fisheri ). The parthenogenetic female also differs from that of F. pohutukawa (conoid tail, with a narrowly rounded tip); F. janetae n. sp., F. indica , F. magna and F. rileyi (longer and more slender tails); and F. armillarisae , F. decorae , F. floribundae , F. leptospermum , F. minimus , F. nervosae , F. pauciflorae n. sp., F. philippinensis , F. sporangae and F. tolgaensis (sub-cylindroid tails). The parthenogenetic female of F. obliquae n. sp. is separated from that of both F. colbrani and F. leucadendrae in having a tail tip that is more narrowly rounded. The female of F. obliquae n. sp. lacks the extensile uterus of F. linariifoliae ; and differs from that of F. robustae n. sp. in having a less curved body shape, a broader tail, and flat vs raised vulval lips.

The infective female of F. obliquae n. sp. differs in shape (arcuate) from that of F. dealbatae , F. diversifoliae , F. fasciculosae , F. gomphocephalae , F. leucadendrae , F. nervosae , F. pimpamensis , F. philippinensis , F. sporangae , and F. viminalisae (open C-shape); and F. floribundae and F. morrisae (J shape). In length (341–355 µm), the infective female is smaller than that of F. brittenae (375–550 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. floribundae (357–450 µm), F. juliae (396–550 µm), F. leptospermum (376–382 µm), F. magna (537–633 µm), F. minimus (419–458 µm), F. pimpamensis (369–443 µm), F. ptychocarpae (387–471 µm), F. rileyi (378–433 µm), and F. tumifaciens (354–445 µm); and larger than that of F. armillarisae (279–291 µm), F. cajuputiae (239–309 µm), F. decorae (207–256 µm), F. quinquenerviae (259–325 µm), and F. tolgaensis (223–272 µm). The infective female of F. obliquae n. sp. has a sub-cylindroid tail with a broadly rounded tip, separating it from that of F. camaldulensae , F. curriei , F. delegatensae , F. fisheri , F. floribundae , F. leucoxylonae , F. microcarpae , F. pimpamensis , F. planchonianae , F. robustae n. sp., F. rosettae , and F. schmidti (hemispherical tip); F. pruinosae n. sp. (with notched tip); and F. porosae (bluntly rounded tip). The infective female of F. obliquae n. sp. may have a longer tail than that of F. viridiflorae (n=1) (23 vs 27–30 µm). Similarly, using Siddiqi’s (1994) description, the infective female of F. obliquae n. sp. may be less curved when heat fixed than that of F. brevicauda , and the ratio c’ is smaller in F. brevicauda (1.6–1.8 vs 0.9–1.1), i.e., the tail is relatively broader. The infective female of F. obliquae n. sp. has a relatively narrower tail than that of F. colbrani (c’ 1.6–1.8 vs 0.8–1.2), and a more cylindroid tail than occurs in that of F. linariifolia . It also lacks the raised circum-oral area of the infective female of F. linariifolia .

In having an open C-shaped body, the male of F. obliquae n. sp. differs from that of F. brittenae , F. curriei , and F. fasciculosae (J-shape); F. armillarisae , F. colbrani , F. cosmophyllae , F. decorae , F. eugenioidae , F. leucoxylonae , F. linariifoliae , F. microcarpae , F. pauciflorae n. sp., F. rileyi , and F. viminalisae (arcuate); and F. diversifoliae , F. juliae , F. magna , F. planchonianae , F. ptychocarpae , and F. viridiflorae (with strongly curved posterior). In size (length 355–448 µm), the male is smaller than F. janetae n. sp. (639–750 µm) and usually smaller than F. magna (446–588 µm), and larger than F. decorae (205–287 µm), F. gomphocephalae (228–283 µm), F. leucadendrae (254–350 µm), F. leucoxylonae (251–293 µm), F. nervosae (277–312 µm), F. porosae (270–326 µm), F. quinquenerviae (256–329 µm), F. rosettae (246–319 µm), and F. tolgaensis (268–349 µm). The length of the tail in the male of F. obliquae n. sp. is longer than in F. tumifaciens (32–46 vs 18–25 µm). The shape of the tail (arcuate, conoid, with a bluntly rounded tip) differs from that of F. philippinensis (truncate tip) and F. rileyi (slender, straight, with bluntly rounded tip). In having an angular spicule, the male of F. obliquae n. sp. differs from that of F. jambophila and F. pimpamensis , with an arcuate spicule. The spicule form in F. obliquae n. sp. is more slender than in the male of F. pruinosae n. sp., which has a stocky, stout spicule. In the male of F. obliquae n. sp., the bursa arises at 50–80% of body length, separating it from F. brevicauda , F. cosmophyllae , F. decorae , F. fisheri , F. minimus , F. nervosae , F. porosae , F. robustae , F. rosettae , F. sporangae , F. schmidti , and F. tumifaciens , in which the bursa is shorter. Fergusobia obliquae n. sp. is also separated from F. leptospermum , F. linariifoliae , F. pohutukawa , F. rileyi , and F. viridiflorae , in which the bursa is longer. In the male of F. obliquae n. sp. the bursa is smooth, but it is crenate in F. delegatensae . Morphologically, it is difficult to separate males of F. obliquae n. sp. and F. camaldulensae, but it lacks the distinctly peaked head capsule of F. camaldulensae and tends to have a smaller stylet (8.5–11 (mean 9) µm in males of F. obliquae n. sp. vs 10–13 (mean 12) in F. camaldulensae ). The head capsule of male F. obliquae n. sp. is slightly raised vs flat in male F. morrisae , but otherwise it is difficult to separate them.

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

Figures

FIGURE5. Fergusobiaobliquaen.sp. exE.obliqua (all inlateral view): A, Entire parthenogeneticfemale; B, Entireinfective female; C, Entire male; D, Anterior end of parthenogenetic female; E, Anterior end of male; F, Habitus of parthenogenetic females; G; Tails of parthenogenetic females; H, Tails of infective females; I, Habitus of infectivefemales; J, Tails of males; K, Spicules.Scale bars: A, B, C = 50 µm; D, E = 10 µm; K = 5 µm. G and J are diagrammatic.