Fergusobia eugenioidae, Davies, Kerrie, Giblin-Davis, Robin, Ye, Weimin, Taylor, Gary & Thomas, Kelley, 2012

Davies, Kerrie, Giblin-Davis, Robin, Ye, Weimin, Taylor, Gary & Thomas, Kelley, 2012, Nematodes from galls on Myrtaceae. III. Fergusobia from flower bud and stigma galls on Eucalyptus, with descriptions of four new species, Zootaxa 3532, pp. 1-36 : 7-11

Description of Fergusobia eugenioidae n. sp. Davies

( Figs 3 , 7 B, 8A)

Measurements. See Table 2 .

Material examined. The description presented here is based on measurements of 10 parthenogenetic females, 10 males, and 1 infective female from flower bud galls on Eucalyptus eugenioides Sieber ex Sprengel , associated with an undescribed species of Fergusonina ; from the Australian National Botanic Gardens, Black Mountain, Canberra, Australian Capital Territory (35°20´S 148°57´E), collected by Kerrie Davies and Mike Hodda, 15.ix.2003.

Holotype. Parthenogenetic female, with a paratype 3 and infective Ƥ, on a slide deposited at the Australian National Insect Collection ( ANIC), Canberra, Australian Capital Territory, Australia, collection data as above.

Paratypes. Vouchers deposited at the Waite Insect and Nematode Collection ( WINC), the University of Adelaide, Adelaide, South Australia, slides number 004312; and the USDA Nematode Collection, Beltsville MD, USA.

Description. Parthenogenetic female. Arcuate, C- or open C-shape when heat-relaxed, dorsally curved with ventral side convex, particularly in tail region; smaller than amphimictic pre-parasitic female and males; body tapers gradually behind vulva. Cuticle with obscure annules ~1 µm wide, longitudinal striae apparent when viewed with light microscope; lateral fields not seen.

Cephalic region ~70–80% diameter of body at anterior end, offset, unstriated, 2 µm high; in lateral view has rounded outline with circum-oral area raised. Stylet 8–11 µm long, with conus 40% of length, basal knobs ~2 µm wide at base, round.

Orifice of dorsal oesophageal gland 1–2 µm posterior to stylet knobs. Anterior fusiform part of digestive tract occupying ~40–70% of body diameter, length 3.1 (2.5–3.6) times diameter; lumen of tract broadening at ~70% length of dorsal oesophageal gland. Oesophageal glands extending over intestine, large, diameter ~50–65% of body diameter, distance from head to end of glands being 42 (34–48)% of total body length.

Secretory/excretory pore at ~30% length of oesophageal gland and anterior to the gland nucleus; with nonrefractile duct leading to oval secretory/excretory cell ~3 µm long. Hemizonid immediately anterior to secretory/ excretory pore.

Reproductive tract usually extending to part-way along dorsal oesophageal gland, to vicinity of secretory/ excretory pore in some specimens and to base of oesophageal gland in one specimen; may be flexed at base of oesophageal glands; oviduct with oocytes not in rows; uterus containing no eggs (in 8 of 9 specimens examined) or one egg; vulva with flat or slightly protruding lips. Tail conoid, length 1.5–3 times anal body diameter, bluntly rounded tip.

Infective pre-parasitic female. Infecting mature larval stage of Fergusonina sp. or pupa. Body arcuate when heat-relaxed, greatest curvature behind vulva; maximum diameter at mid-body length. Cuticle with inconspicuous annulations, longitudinal striae apparent when viewed with light microscope; lateral fields absent.

Cephalic region occupying 70% of body diameter at anterior end, offset, ~2 µm long; circum-oral area raised; stylet slender, 9 µm long, weakly sclerotised with round basal knobs ~2 µm wide; conus 40% of length.

Orifice of dorsal oesophageal gland not seen; oesophageal glands diameter 24% of body diameter, extending over intestine, distance from head to end of glands 20% of total body length. Anterior fusiform part of digestive tract diameter 23% of body diameter, length 3.5 times diameter.

Secretory/excretory pore and cell not seen. Hemizonid not seen.

Uninseminated; vagina perpendicular to body axis; reproductive tract extending to nerve ring; not hypertrophied. Vulval lips almost flat. Tail short, curved on dorsal side, length 1.9 times diameter at anus, tip broadly rounded to almost hemispherical.

Male. Body just J-shaped when heat-relaxed, tail region more or less curved ventrally. Cuticle weakly annulated, annules ~1.2 µm wide, longitudinal striae apparent when viewed with light microscope; lateral fields not seen.

Cephalic region occupying 75–90% of body diameter at anterior end, offset, 2–3 µm long; circum-oral area flat or raised, with lightly sclerotised framework; stylet 9–11 µm long, with conus 40–50% of length, stylet knobs rounded, slightly longer than wide, 1.5 µm wide at base.

Anterior fusiform part of digestive tract diameter 46–54% of body diameter, length 3–3.8 diameter. Oesophageal glands diameter ~25–50% of body diameter, extending over intestine, distance from head to end of glands 26-40% of total body length. Lumen of intestine broadens near base of gland.

Secretory/excretory pore opening 82–101 µm behind anterior end, at 50–60% length of oesophageal gland; secretory/excretory cell not seen. Hemizonid extending over 2–3 annules, immediately anterior to secretory/ excretory pore.

Testis single, variable in length, extending to nerve ring or further anterior; flexed in vicinity of nerve ring; testis, seminal vesicle and vas deferens not clearly differentiated. Bursa usually smooth, crenate in one specimen, peloderan; prominent or obscure; anterior 23 – 25% of body length from tail. Spicules paired, angular near middle, moderately sclerotised; manubrium not offset, of similar diameter to shaft; blade tapering gradually, notched near tip on the proximal edge, opening terminal. Inconspicuous muscles associated with cloaca. Tail curved, ventrally concave, tapering quickly, length 1.85–2.3 times diameter at cloaca; tip broadly rounded.

Diagnosis and relationships. Fergusobia eugenioidae n. sp. is morphologically characterized by the combination of an arcuate, open C- or C-shaped parthenogenetic female with a conoid tail with a bluntly rounded tip; an arcuate to open C-shaped infective female with a hooked tail region and a broadly rounded tail tip, and arcuate to just J-shaped males with angular spicules and short bursa arising at ca 25% of body length. Parthenogenetic females are morphologically similar to those of F. camaldulensae Davies 2012 , F. juliae n. sp. and F. philippinensis Siddiqi 1994 . Infective females are similar to F. juliae n. sp., F. ptychocarpae and F. philippinensis . Males are similar to F. brittenae and F. tumifaciens Currie 1937 .

Parthenogenetic females of F. eugenioidae n. sp. differ in shape (arcuate to open C to C) from F. rileyi Davies (almost straight to arcuate). The shape of the body behind the vulva (arcuate, conoid, with bluntly rounded tip) separates parthenogenetic females of F. eugenioidae n. sp. from those of F. magna ( Davies et al. 2010b), F. i n d i c a Siddiqi 1986, F. morrisae n. sp., F. ptychocarpae ( Taylor & Davies 2008) (arcuate, sub-cylindroid, with narrowly to bluntly rounded tip); and from F. pohutukawa Taylor, Davies, Martin & Crosby 2007 (straight, conoid, with narrowly rounded tip, some with mucron). Their body length (298–354 µm) is larger than in F. cajuputiae Davies & Giblin-Davis 2004 (221–273 µm) and F. fasciculosae n. sp. (237–285 µm) and probably smaller than in F. tumifaciens (415 µm). Fergusobia eugenioidae n. sp. lacks the extra lobe or reflex in the oesophageal gland that is found in F. quinquenerviae Davies & Giblin-Davis 2004 . Parthenogenetic females of F. eugenioidae n. sp. and F. camaldulensae can be separated by the shape of the anterior fusiform part of the digestive tract; respectively 2.6–3.6 and 1.5–2.3 times as long as wide. The stylet is longer in F. eugenioidae n. sp. than in F. curriei and F. juliae n. sp. (respectively, 8–11 vs 5–8 and 5–7 µm).Tail length (18–27 µm) separates these parthenogenetic females from those of F. f i s h e r i (13–16 µm) and F. tumifaciens (39 µm). The tail tip of F. eugenioidae n. sp. is bluntly rounded, but it is broadly rounded in F. brevicauda Siddiqi 1994 and more narrowly rounded in F. philippinensis . The position of the hemizonid (immediately anterior to the secretory/excretory pore) can be used to separate F. eugenioidae n. sp. from F. brittenae (5–6 annules anterior), F. dealbatae Davies & Giblin-Davis 2004 (4–6 annules anterior), F. leucadendrae Davies & Giblin-Davis 2004 (3–4 annules anterior), F. nervosae Davies & Giblin-Davis 2004 (4 annules anterior), and F. viridiflorae Davies & Giblin-Davis 2004 (4 annules anterior). Parthenogenetic females of F. eugenioidae n. sp. lack the swollen cuticle that occurs in F. jambophila Siddiqi 1986 .

Only one specimen of an infective female of F. eugenioidae n. sp. was examined. In shape (arcuate, with a strongly curved posterior region and a broadly rounded to hemispherical tail tip), it can be separated from the same stage of F. brittenae , F. curriei and F. nervosae (open C-shape); from F. fisheri (just J); F. camaldulensae and F. viridiflorae (arcuate); and F. r i l e y i (almost straight). In length (438 µm), the infective female of F. eugenioidae n. sp. is apparently smaller than those of F. magna (537–633 µm); and larger than F. brevicauda (330–410 µm), F. cajuputiae (239–309 µm), F. dealbatae (307–347 µm), F. fasciculosae n. sp. (268–332 µm), F. leucadendrae (227–291 µm), F. morrisae n. sp. (322–395 µm), F. philippinensis (290–370 µm), and F. quinquenerviae (259–325 µm). Infective females of F. eugenioidae n. sp. have a relatively longer tail than F. ptychocarpae (c’ = 1.9 vs 0.6–0.9) and lack the vulval plate present in F. juliae n. sp.

The shape (arcuate to just J) of heat-killed male F. eugenioidae n. sp. separates it from those of F. curriei , F. juliae n. sp., and F. ptychocarpae (J-shape); F. pohutukawa and F. r i l e y i (almost straight to arcuate); and F. jambophila (almost straight). In length (341–420 µm), the males are shorter than those of F. magna (446–588 µm); and longer than F. fasciculosae n. sp. (274–336 µm), F. nervosae (277–312 µm), and F. quinquenerviae (256–329 µm). The stylet (9–11 µm) is longer than in F. cajuputiae (8 µm). The tail is conoid and arcuate in shape with a bluntly rounded tip, which separates males of F. eugenioidae n. sp. from those of F. philippinensis (truncate tip).

The tail (30–39 µm) is longer than in F. brevicauda (13–25 µm), and shorter than in F. pohutukawa (50–61 µm). The spicule length (23–25 µm) differs from that of F. c a m a l d u l e n s a e (18–22 µm), F. cajuputiae (16–20 µm), F. fisheri (16–20 µm), F. jambophila (15–20 µm), F. leucadendrae (14–17 µm), F. ptychocarpae (19–21 µm), and F. viridiflorae (18–20 µm). Males of F. eugenioidae n. sp. have a much shorter bursa than F. morrisae n. sp. The position of the hemizonid (immediately anterior to the secretory/excretory pore) separates males of F. eugenioidae n. sp. from those of F. dealbatae (3 annules distant). Males of F. eugenioidae n. sp. appear to be slimmer than those of F. tumifaciens (a= 10.6–12.8 vs 8–9), and to have a shorter bursa (23–25% of body length vs ‘bursa arises well in front of cloaca’ (Currie, 1937)). They can be separated from F. brittenae by the presence of the large excretory cell which does not occur in F. eugenioidae n. sp., and on tail length relative to diameter (c’ 1.5–2.3 in F. eugenioidae n. sp. vs 0.7–1.4 in F. brittenae ).

From phylogenetic analyses based on sequences of D2/D3 and COI ( Figs 1 , 2 ), the status of F. eugenioidae n. sp. as a new species is supported by its sequence divergence. The blast search of the 860 bp sequenced from D2/D3 revealed the highest similarity as vouchers 25, 26 and 27 (MSp 38) and 348 (MSp 37) with 98% match, 17–20 bp differences and 5 gaps. The blast search of the 618 bp sequenced from COI revealed the highest similarity with vouchers 4 and 350 ( F. juliae n. sp.), 2 (MSp 27), 67 (MSp 12), and 351 (MSp 39) with 94–95% match, 32–40 bp differences and no gaps.

Etymology. Named for E. eugenioides , the host plant from which the nematodes were collected.

Figures

FIGURE 1. The Bayesian consensus tree inferred from D 2 / D 3 under TVM + I + G model (lnL = 4001.6121; freqA = 0.2903; freqC = 0.1443; freqG = 0.2394; freqT = 0.3259; R (a) = 0.8475; R (b) = 3.4236; R (c) = 1.9889; R (d) = 0.455; R (e) = 3.4236; R (f) = 1; Pinva = 0.522; Shape = 0.5933). Posterior probability values exceeding 50 % are given on appropriate clades. (Tree labels comprise nematode species, location (Australia state code), gall type, host plant species and GenBank accession number.

FIGURE 2. The Bayesian consensus tree inferred from COI under GTR + I + G model (lnL = 3999.9661; freqA = 0.2104; freqC = 0.1017; freqG = 0.1948; freqT = 0.4931; R (a) = 1.2258; R (b) = 7.2392; R (c) = 1.5064; R (d) = 0.0698; R (e) = 4.1806; R (f) = 1; Pinva = 0.5476; Shape = 1.5992). Posterior probability values exceeding 50 % are given on appropriate clades.

FIGURE 3. Fergusobia eugenioidae n. sp. (all in lateral view): A, Entire infective female; B, Head of infective female; C, Entire parthenogenetic female; D, Head of parthenogenetic female; E, Tails of parthenogenetic females; F, Entire male; G, Head of males; H, Tails of males. Scale bars: A, C, F = 50 μm. B, D, G = 5 μm. Tails not drawn to scale. Line drawings indicate ranges of habitus of the various stages.

FIGURE 7. Habitus drawings of Fergusobia spp. (most undescribed) collected from flower bud galls (P and Q redrawn from Siddiqi 1994): A, F. ptychocarpae from C. ptychocarpa; B, F. eugeniodae n. sp. from E. eugenioides; C, F. j u l i a e n. sp. from E. macrorrhyncha; D, MSp 27 from E. obliqua; E, MSp 65 from E. obliqua; F, MSp 64 from E. pauciflora; G, F. tumifaciens from E. bridgesiana (formerly stuartiana); H, MSp 54 from E. tereticornis; I, F. fasciculosae n. sp. from E. fasciculosa; J, F. morrisae n. sp. from E. fibrosa; K, MSp 71 from E. largiflorens; L, MSp 72 from E. melliodora; M, Msp 22 from E. microcarpa; N, Msp 75 from E. populnea; O, Msp 62 from E. pruinosa; P, F. brevicauda from E deglupta; Q, F. philippinensis from E. deglupta. Scale bars = 50 μm. MSp numbers as in Davies et al. (2012).