Fergusobia magna

Davies, Kerrie A., Giblin-Davis, Robin M., Ye, Weimin, Taylor, Gary S. & Thomas, Kelley, 2010, Nematodes from galls on Myrtaceae. I. Fergusobia / Fergusonina galls on Corymbia spp., with re-description of F. m a g n a and notes on its phylogenetic relationships, Zootaxa 2634, pp. 25-40 : 29-34

Re-description of Fergusobia magna

( Figs 1–15 , 18 )

Measurements. Table 2.

Parthenogenetic females Males Infective females

mean±s.d. range mean±s.d. range mean±s.d. range

n 30 25 20

L 576±78.1 418–689 527±32.2 446–588 597±23.8 537–633 a 13.1±2.3 8.1–16.1 13.0±1.2 10.5–15.5 15.9±0.9 13.8–17.7 b’ 5.5±1.2 4.2–8.8 3.9±0.5 2.5–4.6 5.9±1.2 4.3–7.9 c 8.8±2.1 6.3–14.2 7.0±0.7 6.3–9.6 6.9±0.7 4.6–7.5 c’ 3.4±0.6 2.5–4.8 2.6±0.3 2.0–3.3 4.2±0.6 3.7–6.5 V/T 82.4±2.6 76.6–88.8 70.3±5.4 61.8–86.9 59.1±3.2 50.9–62.3 Diameter 45±7.2 41–64 41±3.6 33–50 38±1.2 35–41 Stylet length 9.8±1.1 8.1–11.0 10.9±0.9 9.5–13.2 10.9±0.7 9.6–12.5 Head to SE pore 127±25.4 89–182 133±13.1 109–152 148±13.1 111–170 Tail length 68±12.6 44–96 75±8.0 54–87 89±11.6 78–132 Spicule length 33.6±2.2 29.9–37.2

Material examined. The description presented here is based on measurements of 30 parthenogenetic Ƥs, 20 infective Ƥs and 25 3s; Centenary Lakes, Cairns, 16º54’S 145º45’E. Taken from axial bud galls on C. tessellaris . Coll. Kerrie Davies (KD) and Robin Giblin-Davis (RG-D), 15.vii.2004.

One parthenogenetic female, one infective female and a male on a slide deposited in the Australian National Insect collection ( ANIC), Canberra, ACT, Australia, collection data as above.

Vouchers (collection data as above) deposited at the Waite Insect and Nematode Collection ( WINC), The University of Adelaide, SA, Australia, 6 parthenogenetic females, 5 infective females and 11 males on slides numbered 004354-6, 0 63696 (WNC 2384); at the Queensland Museum, Brisbane, Queensland, Australia 13 parthenogenetic females, 10 infective females and 5 males on slides; and at the USDA Nematode Collection, Beltsville, MD, USA 5 parthenogenetic females, 5 infective females and 4 males on slides.

Other material examined. About 40 parthenogenetic females, 5 males, and various juveniles from gall forms on C. tessellaris as above, from various sites from coastal eastern Queensland: Sherwood Arboretum, Brisbane, 27º32’S 152º58’E, coll. RG-D, 1.viii.1999 (slides numbered 0 0 4335 (WNC 2073)); roadside at Groper Creek, 19º42’S 147º32’E, coll. KD, 6.vi.2002 (slides numbered 0 63697 (WNC 2241)); Ellis Beach, 16º43’S 145º39’E, coll. KD, 9.v.2002 (slides numbered 0 63699 (WNC 2245)); Cardwell Beach, 18º16S 146º01’E, coll. RG-D, 27.v.1999 (slides numbered 0 0 4351 (WNC 2055)); Cardwell Beach, 18º15’S 146º01’E, coll. KD and RG-D, 14.vii.2004 (slides numbered 0 63695 (WNC 2394)); Norm Byrnes Arboretum, Mission Beach, 17º95’S 146º08’E, coll. KD, 14.vii.2004 (slides numbered 0 0 4354 (WNC 2396, 2488)); Hervey Bay, 25º29’S 152º85’E, coll. KD and RG-D, 24.vii.2008 (slides numbered 0 63817 (WNC 2504)). These are deposited in the WINC.

Description. Parthenogenetic female. Body shape variable, arcuate to C or S-shaped, usually dorsally curved with ventral side convex to form open C-shape; relatively large (418–689 µm); relatively slender (a = 8–18); similar in size to amphimictic pre-parasitic females and to males; body narrows behind vulva to form relatively long, slender tail ( Figs 1, 2 ). With light microscope, cuticle appears smooth, sub-cuticle with strong longitudinal striae. Lateral fields not seen. ‘Deirids’ present at level of stylet knobs.

Cephalic region ~80% diameter of body at anterior end, off–set, 2 µm high, unstriated; rounded outline in lateral view, circum-oral area raised ~1 µm ( Fig. 3 ). With SEM, en face cephalic region has 6 rounded sectors arranged relatively evenly around slightly elevated circum-oral area, dorsal and ventral sectors narrow, often not apparent ( Figs 13, 14 ). Amphids not seen, but 6 cephalic papillae, each situated near the mid-point of the respective rounded sectors, are present. Stylet 8–11 µm long, with cone 40–50% length, basal knobs just higher than wide, 2–3 µm wide at base, rounded.

Orifice of dorsal pharyngeal gland 1–2 µm posterior to stylet knobs. Anterior fusiform part of digestive tract occupying 33–74% (mean 43%, n = 12) body diameter, ~3 times longer than wide; lumen of tract broadens at distal end of dorsal pharyngeal gland. Pharyngeal glands often obscure, occupying 32–65% (average 51%, n = 10) of body diameter, extending 11–30% (mean 18%) of total body length. Gland nucleus large, with medium-sized nucleolus. Prominent nuclei present in intestinal walls.

Secretory/excretory pore 71–166 µm from anterior end; duct obscure, opens opposite nucleus of pharyngeal gland; secretory/excretory cell not seen. Hemizonid extending over two annules, ~25 annules in front of secretory/excretory pore.

Reproductive tract variable in length, extending to secretory/excretory pore, part-way along pharyngeal gland or to nerve ring; flexed in 29/ 30 specimens examined; oviduct usually with two oocytes in a row; quadricolumella smooth, uterus long and extensile, usually with 2 or more eggs and often juveniles, surrounded by strong muscles anterior to vulva; vulva a simple transverse slit with protruding lips in some specimens; no vulval plate. Probably ovoviviparous. Anus pore-like. Tail relatively long (c = 6.3–14.2), conoid, concave on ventral side; 2.5–5 longer than anal body diameter; tip narrowly rounded ( Fig. 4 ).

Infective pre-parasitic females. Infects mature larval stage of Fergusonina sp. or pupa. Arcuate shape when relaxed by heat; relatively slender (a = 14–18); maximum body diameter at mid-body length in region of vulva; body tapers gradually in tail region ( Figs 5, 6 ). Cuticle obscurely annulated, less than 1 µm wide; longitudinal striae apparent with light microscope; lateral fields not seen.

Cephalic region not offset, domed shape; circum-oral area rounded; stylet slender, 9–10 µm long, weakly sclerotised with retrorse basal knobs higher than wide; ~2µm wide; cone ~50% of length ( Fig. 7 ).

Orifice of dorsal pharyngeal gland often obscure, 1–2 µm posterior to stylet knobs. Anterior fusiform part of digestive tract little expanded, occupying 34–42% of body diameter, 3.9–5.5 times as long as wide (n = 7). Pharyngeal glands occupying 13–53% (mean 28%) body diameter (n = 6), extending over intestine to average 17 (13–23%) body length.

Secretory/excretory pore opens 111–170 µm from anterior end, behind pharyngeal glands; duct obscure; ellipsoid secretory/excretory cell ~15 µm long. Hemizonid extends over two annules, ~two annules in front of secretory/excretory pore.

Uterus ~70% of total gonad length in uninseminated females, packed with sperm in inseminated females; vagina at right angle to body axis; reproductive tract extending to dorsal pharyngeal gland; hypertrophy of tract in some specimens. Vulva a transverse slit, vulval lips raised ~1 µm, a vulval plate present. Anus an obscure pore. Tail relatively long (c= 4.6–7.5), conoid; 3.7–6.5 longer than diameter at anus, tip pointed ( Fig. 8 ).

Male. Body arcuate or J-shape when relaxed by heat, tail region more or less curved ventrally ( Figs 9, 10 ). Cuticle separated from body wall after fixation in some specimens, clearly annulated, annules ~1µm wide; strong longitudinal striae apparent with light microscope; lateral fields not seen; ‘deirids’ not seen.

Cephalic region occupying 80–90% anterior body diameter, offset, ~2 µm high; circum-oral area flat or raised, with lightly sclerotised framework; stylet 10–12 µm long, with cone 40% of length, round stylet knobs 2–3 µm wide ( Fig. 11 ). Anterior fusiform part of digestive tract occupying 29–43% of body diameter, 4–5 times longer than wide. Orifice of dorsal pharyngeal gland 2–3 µm behind knobs. Pharyngeal glands often obscure; occupying 20–50% (mean 34.2%) of body diameter (n = 10), extending over intestine to 22–40% (mean 36%) of total body length. Lumen of intestinal tract broadens behind pharyngeal gland. Prominent nuclei present in intestinal walls.

Secretory/excretory pore opens 107–152 µm behind anterior end, opposite nucleus of pharyngeal gland; duct obscure; secretory/excretory cell ~5 µm long. Hemizonid lens-like, extending over two annules, two to three annules in front of secretory/excretory pore.

Reproductive tract with single testis, variable in length, may extend to nerve ring but usually overlaps dorsal pharyngeal gland; may be reflexed; testis, seminal vesicle and vas deferens not clearly differentiated. Bursa peloderan (but may appear to be leptoderan, as diameter drops markedly ~10 µm from the tail tip), smooth; may be prominent or obscure; arises 30 – 47% along length of body. Spicules paired, angular at about 33% of length, with manubrium and shaft longer than blade; moderately sclerotised; manubrium similar to or wider than shaft, not offset; blade narrows gradually to bluntly rounded tip with concavity on distal edge; opening terminal ( Figs 9 , 15 ). Inconspicuous muscles associated with cloaca. Tail arcuate, ventrally concave, conoid; 2–3.3× as long as diameter at cloaca; rounded tip ( Fig. 12 ).

Diagnosis (Emended). Fergusobia magna is morphologically characterized by the combination of a relatively large, variably shaped parthenogenetic female with a slender conoid tail and rounded pointed tip; a relatively large arcuate infective female with a long slender tail with a pointed tip and a relatively anterior vulva; and a relatively large, arcuate, open C or J-shaped male with spicules angular at about 33% of their length, slender tail and mid-length peloderan bursa. From phylogenetic analyses based on sequences of D2/ D3 and COI, there was a well-supported clade (100% Bayesian, 100% NJ, 100% MP) of six isolates of F. magna from north-eastern and south-eastern Queensland ( Figs 16–17 ).

Siddiqi (1986) described F. m a g n a from parthenogenetic females only from galls on a twig of Eucalyptus sp. at Indooroopilly, Queensland. Galls meeting the description given by Siddiqi are found on most specimens of C. tessellaris , which grows commonly in the Indooroopilly area and also along the Queensland coast (Davies & Giblin-Davis, unpub. obs.). The galls are terminal and axial shoot bud galls, but the leaves have dehisced and the galls appear to be ‘stem’ galls. Parthenogenetic females collected from the galls in this study generally fit the description given by Siddiqi. They have similar body length (here 418–619 µm vs Siddiqi’s 500–780 µm); tail length (44–96 µm vs 60–95 µm); tail shape (elongate, conoid, tapering to small rounded tip); V (77–89 vs 81%); ratio a (8–18 vs 12–18); ratio c (6.3–14.2 vs 6.6–10.5); and ratio c’ (2.5–4.8 vs 3.6– 4.8). Scanning electron micrographs of the cephalic region of F. m a g n a from the collections described here (drawn in Figs 13, 14 ) suggest that it is less laterally compressed than is apparent in Siddiqi’s (1986) micrograph. However, this may reflect differences in the quality of the preparation of the micrographs. Therefore, because the parthenogenetic female nematodes collected here from C. tessellaris generally meet the description and diagnosis given by Siddiqi, and despite lack of precise data on gall form, plant and insect host species, morphology and morphometrics of male and pre-infective female nematodes, and collection site, the nematodes are here re-described as F. magna .

In having parthenogenetic females that are longer (418–689 µm) than F. brevicauda Siddiqi, 1994 (260– 390 µm), F. c u r r i e i Fisher & Nickle 1968 (275–370 µm), F. cajuputiae Davies & Giblin-Davis 2004 (221–273 µm), F. dealbatae Davies & Giblin-Davis 2004 (250–410 µm), F. f i s h e r i Davies & Lloyd, 1996 (228–305 µm), Davies & Giblin-Davis 2004 (245–309 µm), F. jambophila Siddiqi, 1986 (195–300 µm), F. leucadendrae Davies & Giblin-Davis 2004 (205–303 µm), F. nervosae Davies & Giblin-Davis 2004 (245– 309 µm), F. philippinensis Siddiqi 1996 (229–310) µm, F. pohutukawa Taylor, Davies, Martin & Crosby, 2007 (244–365 µm), F. quinquenerviae Davies & Giblin-Davis 2004 (224–324 µm), F. tumifaciens ( Currie 1937) Wachek 1955 (415 µm), and F. viridiflorae Davies & Giblin-Davis 2004 (259–328 µm), F. magna differs from all described species of Fergusobia except F. indica ( Jairajpuri, 1962) Siddiqi, 1986 (525–626 µm) and F. ptychocarpae Davies, 2008 (320–461 µm) and F. brittenae Davies, 2010 (328–461 µm). Parthenogenetic females of F. magna are separated from F. indica by the form of the cephalic region (dome-like in F. indica ), by having a shorter stylet (8–11 µm vs 12–15 µm), and because the latter is not ovoviviparous. Fergusobia ptychocarpae and F. brittenae have a shorter tail than F. magna (respectively, tail length = 13–46 µm and 23– 37 µm vs 44–96 µm; and c = 14 (8–27) and 15 (10–19) vs 8 (6.6–10.5)).

On the basis of body length, infective females of F. magna can be separated from other described species of Fergusobia where the stage is known (537–633 µm vs 330–410 µm in F. brevicauda , 417–489 µm in F. curriei , 239–309 µm in F. cajuputiae , 307–347 µm in F. dealbatae , 241–395 µm in F. f i s h e r i, 227–291 µm in F. leucadendrae , 282 µm in F. nervosae , 290–370 µm in F. philippinensis , 259–325 µm in F. quinquenerviae , and 321 µm in F. viridiflorae ) except F. brittenae (375–550 µm). The position of the vulva in infective females of F. magna (51–63%) is more anterior than in other described species of Fergusobia (76–85 in brevicauda , 72–77 in F. brittenae , 76–82 in F. c u r r i e i, 81–86 in F. cajuputiae , 80–84 in F. dealbatae , 76–88 in F. f i s h e r i, 80–81 in F. leucadendrae , 82 in F. nervosae , 70–82 in F. philippinensis , 79–87 in F. quinquenerviae , and 79% in F. viridiflorae ).

The size and form of the spicule in male F. magna separates it from all other described species of Fergusobia . In length (30–37 µm), the spicule is longer than in F. brevicauda (21–27 µm), F. brittenae (19–25 µm), F. cajuputiae (16–20 µm), F. dealbatae (18–22 µm), F. f i s h e r i (16–20 µm), F. jambophila (15–20 µm), F. leucadendrae (14–17 µm), F. nervosae (16–19 µm), F. philippinensis (19–23 µm), F. pohutukawa (19–24 µm), F. ptychocarpae (19–21 µm), F. quinquenerviae (16–20 µm), F. tumifaciens (21 µm), and F. viridiflorae (18–20 µm). In having spicules with manubrium and shaft forming 66% of their length, and separated from the blade by an angle, F. magna differs from other described species in which the angle in the spicule is at about 50%, or the spicule is arcuate.

Figures

FIGURE 16. The 10001 st Bayesian tree inferred from 28 S D 2 / D 3 under TVM + G model (lnL = 2116.6306; freqA = 0.2878; freqC = 0.1496; freqG = 0.2413; freqT = 0.3212; R (a) = 0.9996; R (b) = 3.7074; R (c) = 2.0173; R (d) = 0.3183; R (e) = 3.7074; R (f) = 1; Pinva = 0; Shape = 0.3069). Posterior probability values exceeding 50 % are given on appropriate clades, the other values are absolute nucleotide differences.

FIGURE 17. The 10001 st Bayesian tree inferred from mitochondrial DNA cytochrome oxidase subunit I under GTR + I model (lnL = 1554.5043; freqA = 0.2072; freqC = 0.1201; freqG = 0.1866; freqT = 0.4861; R (a) = 0.0529; R (b) = 5.5166; R (c) = 1.729; R (d) = 0.5022; R (e) = 2.9846; R (f) = 1; Pinva = 0.6478; Shape = equal). Posterior probability values in bold exceeding 50 % are given on appropriate clades, the other values are absolute nucleotide differences.

FIGURES 1 – 12. Fergusobia magna ex C. tessellaris. Parthenogenetic female. 1: Entire female. 2: Habitus. 3: Head and stylet. 4: Tail shapes. Infective female. 5: Entire female. 6: Habitus. 7: Head and stylet. 8: Tail shapes. Male. 9: Entire male. 10: Habitus. 11: Head and stylet. 12: Tail shapes. Scale bars 1, 5, 9 = 50 µm; 3, 7, 11 = 5 µm.

FIGURES 13 – 15. Fergusobia magna ex C. tessellaris. 13: Drawing of scanning electron micrograph showing lateral view of head. Arrows indicate dorsal and ventral sectors. 14: Drawing of scanning electron micrograph showing semi- en face view of head. 15: Spicules. Scale bars = 5 µm.

FIGURES 18 – 23. Habitus of Fergusobia magna ex C. tessellaris and Fergusobia spp. collected from other Corymbia spp. 18: Parthenogenetic female, male and infective female of F. magna. 19: Parthenogenetic female of Fergusobia sp. ex C. citriodora subsp. variegata. 20: Parthenogenetic female and male of Fergusobia sp. ex C. intermedia. 21: Parthenogenetic female, male and infective female of F. ptychocarpae ex C. ptychocarpa. 22: Parthenogenetic female of Fergusobia sp. ex C. trachyphloia. 23: Parthenogenetic female, male and infective female of Fergusobia sp. ex Corymbia sp. Scale bars = 50 µm.