Fergusobia janetae 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 : 3-7

Fergusobia janetae Davies n. sp. apud MSp 40 ( Davies et al. 2012a)

( Fig. 1 )

Measurements. Table 2.

Material examined. Holotype: Parthenogenetic female, near Busselton, WA, Australia (33°38.62´S, 115°26.59´E). From roadside vegetation; unilocular galls on the blades of leaves of Eucalyptus marginata Donn ex Smith , collected J. Walker and K.A. Davies, 30.x.2000. 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, 8 parthenogenetic ♀ s and 6 Ƌs on slides numbered WINC 004288-89 ( WNC 2209 ) ; at the Western Australian Museum , Perth, WA, Australia, 8 parthenogenetic ♀ s and 8 Ƌs on slides; and at the USDA Nematode Collection, Beltsville, MD, USA 1 parthenogenetic ♀ and 1 Ƌ on a slide. Fifteen parthenogenetic ♀ s, one preparasitic infective ♀ and 18 ♂ s examined.

Description. Parthenogenetic female. Body straight to arcuate, spindle-shaped; relatively broad compared to length; of similar size to males; body narrows gradually from about one body diameter anterior to vulva to form a straight conoid tail ( Fig. 1A ). With light microscope, cuticle appears smooth, and longitudinal striae in sub-cuticle are clear. Lateral fields with seven incisures ( Fig. 1K ).

Cephalic region 6–9 µm in diameter, ~75–80% diameter of body at anterior end, off-set, 1.5 – 3 µm high, unstriated, not annulated; rounded outline in lateral view, circum-oral area slightly raised ( Fig. 1B ). Scanning electron microscopy shows that there are 6 rounded ‘lips’, with the two lateral lips being slightly narrower than the other four, and sub-triangular, with large openings for the amphids ( Fig. 1B ). Stylet sturdy, with cone usually less than 50% length, basal knobs as high as wide, ~ 2 µm wide at base, rounded.

Orifice of dorsal pharyngeal gland ~ 1 µm posterior to stylet knobs. Anterior fusiform part of digestive tract not greatly expanded, occupying ~50–80% of body diameter; length 4.6 (3.7–6.0) times diameter ( Fig. 1B ). Valves apparently separating pharynx and intestine present 1–1.2 stylet lengths behind the stylet knobs, i.e. within the anterior fusiform part of digestive tract. Pharyngeal glands large, extending over intestine, occupying 57 (48–67)% of body diameter, distance from anterior end to end of glands being 20 (12–25)% of total body length. Intestinal lumen broadens from mid length to posterior of pharyngeal gland.

Secretory/excretory pore opening posterior to pharyngeal gland; with non-refractile duct surrounded by prominent duct cell, secretory/excretory cell ellipsoid. Hemizonid positioned far anterior to pore, approximately at level of nucleus of dorsal gland cell.

Reproductive tract variable in length, outstretched or flexed, extending part-way along dorsal pharyngeal gland or to nerve ring; oviduct with oocytes in pairs; uterus relatively long, extensile; about 30% of body length, containing 3 or more eggs; cells of quadricolumella prominent, smooth; vulva a simple slit. Anus a small pore. Tail conoid, straight, length 2–5 times anal body diameter, strongly annulated, narrowing gradually and equally to bluntly rounded tip ( Figs 1A, G ).

Infective pre-parasitic female. The only specimen found was undergoing moult from J4 to adult stage ( Fig. 1C ). Infects mature larval stage or pupa of Fergusonina sp. Almost straight when relaxed by heat; maximum diameter at mid-body length, body narrows gradually behind vulva. Cuticle with inconspicuous annulations, clear longitudinal striae seen with light microscope; lateral fields not seen. Large nuclei present in body wall.

Cephalic region ~ 90% diameter of body at anterior end, not offset, unstriated, ~ 8 µm in diameter, 2 µm high; circum-oral area flat. Stylet too weakly sclerotised to be observed.

Orifice of dorsal pharyngeal gland not seen. Anterior part of digestive tract not expanded, occupying ~60% of body diameter, length 5 times diameter. Pharyngeal gland extending over intestine, occupying 40% body diameter, distance from anterior end to posterior end of glands being 22% body length.

Secretory/excretory pore opening near posterior end of pharyngeal glands; hemizonid not seen.

Uterus not fully developed, containing no sperm; vagina angled towards anterior end, about one vulval body diameter in length and occupying almost full body width, ovoid in shape, surrounded by apparent strong musculature; reproductive tract extending ~30% of distance between vulva and nerve ring. Vulval lips tiny, flat; no vulval plate apparent. Tail straight, length ~4 times body diameter at anus, tip narrowly rounded ( Fig. 1C ).

Male. Body an open C-shape when relaxed by heat, tail region relatively slender ( Fig. 1D ). Cuticle appears smooth when viewed with light microscope; longitudinal striae clearly apparent in sub-cuticle; lateral fields faint, 5 or 6 lines present.

Cephalic region 80–90% of anterior body diameter, offset, 6–8 µm in diameter, 2–4 µm high; circum-oral area flat or barely raised. Stylet sturdy, with cone ~40% of length, basal knobs spheroid, ~2 µm wide ( Fig. 1H ).

Anterior fusiform part of digestive tract slender, occupying ~20–40% of body diameter; length 5.1 (4.1–5.9) times diameter; lumen broadening posterior to gland nucleus. Valves apparently separating pharynx and intestine, situated ~1 stylet length behind stylet knobs. Pharyngeal glands extending over intestine, 59 (50–68)% of body diameter, distance from anterior end to end of glands being 24 (20–34)% of total body length.

Secretory/excretory pore opens posterior to pharyngeal gland; duct non-refractile, surrounded by prominent duct cell; excretory cell not seen. Hemizonid extending over two annules, positioned anterior to secretory/excretory pore in region level with or anterior to pharyngeal gland nucleus.

Reproductive tract with single testis, extending to nerve ring; usually outstretched and occasionally flexed; testis, seminal vesicle and vas deferens of shorter tracts not clearly differentiated ( Fig. 1D ). Spermatids not in columns. Bursa smooth, prominent in most specimens; arises 95–98 (mean 96%) of length of body anterior to tail tip ( Fig. 1H ). The bursa widens just anterior to the cloaca; unclear if it terminates just anterior to the tail tip or surrounds it ( Fig. 1D ). Spicules paired, more or less angular near mid-length, relatively slender; relatively strongly sclerotised; in some specimens manubrium clearly offset on dorsal edge, wider than shaft; blade narrows gradually to bluntly rounded tip and may have convex curve on proximal edge ( Fig. 1L ). Large glands on vas deferens, associated with cloaca. Tail straight to ventrally arcuate, sub-conoid, ~3–5 times as long as diameter at cloaca, narrowing gradually to bluntly rounded or angular tip ( Fig. 1J ).

Diagnosis and relationships. Fergusobia janetae n. sp. is morphologically characterized by the combination of a large, almost straight, spindle-shaped parthenogenetic female with an extensile uterus and a narrow conoid tail; an arcuate, relatively broad, infective female with a conoid tail having a narrowly rounded tip; and an open Cshaped male with an arcuate to angular spicule and bursa arising near the level of the stylet knobs. Morphologically, F. janetae n. sp. is most similar to F. magna Siddiqi 1986 sensu Davies 2010 (in Davies et al. 2010b), F. indica ( Jairajpuri, 1962) Siddiqi, 1986 and F. rileyi , and also has similarities with F. linariifolia Davies 2014 (in Davies et al. 2014e) and F. pohutukawa Davies 2007 (in Taylor et al. 2007). Its status as a distinct species is corroborated by molecular data from sequencing of the relatively conserved 18S and 28S D2/D3 expansion segment.

The parthenogenetic female of F. janetae n. sp. (a straight or arcuate spindle-shape when heat-fixed, with a long slender tail) differs from all described species of Fergusobia , except F. magna . Body length of the parthenogenetic female of F. janetae n. sp. overlaps with that of F. magna and F. indica (respectively, 514–723 vs 418–780 and 525–626 µm) and is larger than all other described species of Fergusobia . However, its straight to arcuate body separates female F. janetae n. sp. from F. magna which has a C-shaped parthenogenetic female. The presence of an extensile uterus in the parthenogenetic female of F. janetae n. sp. separates it from F. indica and also from F. cajuputiae Davies & Giblin-Davis, 2004 , F. colbrani Davies 2014 (in Davies et al. 2014a), F. dealbatae Davies & Giblin-Davis, 2004 , F. delegatensae Davies 2013 (in Davies et al. 2013b), F. eugenioidae Davies 2012 (in Davies et al. 2012b), F. fisheri Davies & Lloyd, 1996 , F. leucadendrae Davies & Giblin-Davis, 2004 , F. nervosa Davies & Giblin-Davis, 2004 , F. philippinensis Siddiqi, 1994 , F. schmidti Davies 2014 (in Davies et al. 2014c), F. quinquenerviae Davies & Giblin-Davis, 2004 , F. rosettae Davies 2014 (in Davies et al. 2014d), F. rileyi Davies 2012 (in Davies et al. 2012a), F. sporangae Davies 2014 (in Davies et al. 2014d), F. tolgaensis Davies 2014 (in Davies et al. 2014d), F. tumifaciens ( Currie 1937) Wachek 1955 sensu Davies 2014 (in Davies et al. 2014b), and F. decorae Davies 2014 (in Davies et al. 2014e), which lack extensile uteri. In having cuticle that does not swell upon fixation; it differs from F. linariifoliae and F. pohutukawa , and also from F. jambophila Siddiqi 1986 , in which it does. Fergusobia janetae n. sp. is separated from F. rileyi by both body length and in having a longer tail (90 vs 40–50 µm).

The only infective female of F. janetae n. sp. available for examination was moulting, and information about it is therefore limited. Its body length and stylet length are unlikely to accurately reflect that of mature individuals, i.e., cannot be used here as characters. Its arcuate shape differs from that of F. diversifoliae , F. fasciculosae Davies 2012 (in Davies et al. 2012b), F. gomphocephalae Davies 2014 (in Davies et al. 2014c), F. leucadendrae , F. nervosae , F. pimpamensis Davies 2013 ( Davies et al. 2013b), F. philippinensis , F. rosettae , F. sporangae , F. tolgaensis Davies 2014 (in Davies et al. 2014c), and F. viminalisae Davies 2014 (in Davies et al. 2014b) (open Cshape), and from F. eugenioidae , F. juliae Davies 2012 (in Davies et al. 2012b), F. morrisae Davies 2012 (in Davies et al. 2012b), F. pruinosae n. sp., F. ptychocarpae Davies 2008 (in Taylor & Davies 2008), F. tumifaciens , and F. viminalisae (J-shaped). It has a straight slender sub-conoid tail with a bluntly rounded tip, separating it from F. brittenae Davies 2010 (in Taylor & Davies 2010), F. cajuputiae , F. curriei Fisher & Nickle 1968 , F. leptospermum Davies 2017 (in Davies et al. 2017), F. leucadendrae , F. minimus Lisnawita (in Davies et al., 2013b) , F. nervosae , F. pauciflorae n. sp., F. quinquenerviae , F. tolgaensis (with broadly rounded tips); F. eugenioidae , F. juliae , F. linariifoliae , F. morrisae , F. porosae Davies 2013 (in Davies et al. 2013a), F. pruinosae n. sp., F. ptychocarpae , F. tumifaciens , F. viminalisae , F. viridiflorae Davies & Giblin-Davis 2004 (with J–shaped tails); F. armillarisae Davies 2014 (in Davies et al. 2014), F. brevicauda Siddiqi 1994 , F. camaldulensae , F. colbrani , F. cosmophyllae Davies 2013 (in Davies et al. 2013b), F. dealbatae , F. decorae , F. delegatensae , F. diversifoliae Davies 2013 (in Davies et al. 2013b), F. fasciculosae , F. fisheri , F. floribundae Davies 2013 (in Davies et al. 2013b), F. gomphocephalae , F. leucoxylonae Davies 2014 (in Davies et al. 2014c), F. microcarpae Davies 2013 (in Davies et al. 2013a), F. obliquae n. sp., F. pimpamensis , F. planchonianae Davies 2014 (in Davies et al. 2014b), F. robustae n. sp., F. rosettae , F. schmidti , F. sporangae (with sub-hemispherical tips); and from F. philippinensis (with a truncate tip). The infective female of F. janetae n. sp. has a more posterior vulva than that of F. magna (V% 65–72 vs 51–62).

In length (639–750 µm), the male of F. janetae n. sp. is larger than all described species of Fergusobia . The shape of the tail (slender, arcuate with a bluntly rounded tip, long) is similar to that of F. magna and F. rileyi , but differs in being longer (82–111 vs 54–87 and 58–70 µm, respectively) and is slimmer than in F. magna (respectively, c’ ratio 3.3–4.8 vs 2.0–3.3). In length (9–11 µm), the stylet is similar to that of most described species, but longer than in F. minimus (4–7 µm). Spicule length (23–27 µm) is smaller than in F. magna (30–36 µm); but overlaps with or is longer than in other described species of Fergusobia . The shape of the spicules in F. janetae n. sp. (more or less angular) differs from those of F. jambophila , F. pimpamensis , F. rosettae , and F. decorae , in which it is clearly arcuate. In the male of F. janetae n. sp., the bursa extends over>90% of the body length, longer than in most Fergusobia spp., except for F. leptospermum (99%), F. linariifolia (90%), F. pohutukawa (99%), F. rileyi (90–95%) and F. viridiflorae (90%).

Etymology. Named for the late Janet Walker, who directed the first author to the new species described here, in gratitude for her help with collecting, and happy memories of her zest for life, humour and patience.

Figures

FIGURE 1. Fergusobia janetae n. sp. ex E. marginata (all in lateral view): A, Entire parthenogenetic female; B, Anterior end of parthenogenetic female; C, Entire infective female; D, Entire male; E, Drawing of SEM of anterior end of parthenogenetic female; F, Habitus of parthenogenetic female; G; Tails of parthenogenetic female; H, Anterior end of male; I, Habitus of male; J, Tails of males; K, Lateral lines; L, Spicules. Scale bars: A, C, D = 50 µm; B, H = 25 µm; E, L = 5 µm. Tails and lateral lines not drawn to scale.