Fergusobia decorae, Davies, Kerrie A., Giblin-Davis, Robin M., Ye, Weimin, Taylor, Gary S., Makinson, Jeff & Purcell, Matthew, 2014

Davies, Kerrie A., Giblin-Davis, Robin M., Ye, Weimin, Taylor, Gary S., Makinson, Jeff & Purcell, Matthew, 2014, Nematodes from galls on Myrtaceae. X. Fergusobia from galls on narrow-leaved Melaleuca spp. in Australia, with descriptions of three new species, Zootaxa 3889 (2), pp. 237-258 : 243-247

Description of Fergusobia decorae n. sp. Davies

( Figs 2 , 4 B)

= Fergusobia MSp 48 apud Davies et al. (2012a)

Measurements. Table 3 .

Material examined. The description presented here is based on measurements of 19 parthenogenetic ♀s, 5 infective ♀s and 26 ♂ s; roadside planting, Ingham QLD, Australia (18º38.93’S 146º09.58’E). Taken from unilocular axial bud galls on Melaleuca decora (Salisb.) Britten 1916 . Collected by R.M. Giblin-Davis and K.A. Davies on 18.vii.2004; K.A. Davies & S. Scheffer on 15.viii.2007.

Holotype: One parthenogenetic female, together with an infective female and a male, on a slide deposited in the ANIC, Canberra, ACT, Australia; collection data as above, coll. R.M. Giblin-Davis and K.A. Davies on 18.vii.2004.

Paratypes: Vouchers (collection data as above) deposited at the WINC, The University of Adelaide, SA, Australia, 5 parthenogenetic females, 2 infective females and 10 males on slides numbered WINC 0 63692 (WNC 2386); at the Australian National Museum, Sydney, NSW, Australia, 12 parthenogenetic females, 2 infective females and 10 males on slides; and at the USDA Nematode Collection, Beltsville, MD, USA 2 parthenogenetic females and 5 males on slides.

Holotype Partheno Parthenogenetic Males Infective females

genetic female females

Description. Parthenogenetic female. Body shape arcuate, usually dorsally curved with ventral side convex; relatively small; relatively slender (a = 8–18); similar in size or larger than amphimictic pre-parasitic females and males; body narrows behind vulva to form broadly conoid to sub-cylindrical tail. With light microscope, cuticle appears smooth, sub-cuticle with strong longitudinal striae. Lateral fields not seen.

Cephalic region ~ 80% diameter of body at anterior end, offset, 2 µm high, unstriated; rounded outline in lateral view, circum-oral area raised ~ 1 µm. Stylet short, with cone occupying ~ 30% of stylet length, basal knobs small, rounded, <2 µm wide.

Orifice of dorsal pharyngeal gland ~1 µm posterior to stylet knobs. Anterior fusiform part of digestive tract occupying 53 (44–64)% body diameter, length 2.4–3.7 times diameter; lumen of tract broadens at distal end of dorsal pharyngeal gland. Pharyngeal glands large but often obscure, extending over intestine, occupying 51 (32–65)% of body diameter, distance from head to end of glands being 50 (33–67)% of total body length. Gland nucleus large, with large nucleolus.

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

Reproductive tract variable in length, outstretched, extending to secretory/excretory pore, part-way along pharyngeal gland or to nerve ring; oviduct usually with two oocytes for the first few rows behind the cap cell followed by rows with one; quadricolumella smooth, uterus usually with 1 egg; vulva a simple transverse slit with rounded protruding lips in some specimens; no vulval plate. Anus pore-like. Tail relatively short, sub-cylindrical, concave on ventral side; length 1–2 times anal body diameter; tip broadly rounded.

Infective pre-parasitic female. Infects mature larval stage of Fergusonina sp. or pupa. Arcuate shape when heat-relaxed; relatively broad (small a ratio); maximum body diameter at mid-body length; body tapers gradually behind vulva. Cuticle obscurely annulated, <1 µm wide; longitudinal striae apparent with light microscope; lateral fields not seen.

Cephalic region not offset, dome-shaped; circum-oral area rounded; stylet slender, weakly sclerotised with tiny basal knobs being ~1µm wide; cone occupying ~ 40% of stylet length.

Orifice of dorsal pharyngeal gland often obscure, ~1 µm posterior to stylet knobs. Anterior fusiform part of digestive tract little expanded, occupying 50%–67% of body diameter, length 1.8–3.3 times diameter. Pharyngeal glands extending over intestine, occupying ~ 60% body diameter (n = 2), distance from head to end of glands being 40% (30%–58%) of total body length.

Secretory/excretory pore opens near distal end of pharyngeal glands; duct obscure; ellipsoid secretory/ excretory cell ~ 4 µm long. Hemizonid not seen.

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 nerve ring; hypertrophy of tract in some specimens. Vulva a transverse slit, vulval lips raised, ~ 1 µm, no vulval plate present. Anus an obscure pore. Tail short, conoid; length 1.0–1.5 times diameter at anus, tip broadly rounded.

Male. Body straight to arcuate in shape when relaxed by heat, tail region more or less curved ventrally. Cuticle clearly annulated, annuli ~1µm wide at mid-body length; strong longitudinal striae apparent with light microscope; lateral fields not seen.

Cephalic region occupying 80–90% anterior body diameter, barely offset, ~ 1–2 µm high; circum-oral area flat or raised, with lightly sclerotised framework; stylet with cone 40% of length, round stylet knobs 2–3 µm wide. Orifice of dorsal pharyngeal gland ~ 1 µm behind knobs. Anterior fusiform part of digestive tract occupying 52%–65% of body diameter, length 2.0–3.4 times diameter. Pharyngeal glands extending over intestine, occupying 66 (52–82)% of body diameter, distance from head to end of glands being 43 (32–59)% of total body length. Lumen of intestinal tract broadens behind pharyngeal gland.

Secretory/excretory pore opens opposite nucleus of pharyngeal gland; duct obscure; secretory/excretory cell not seen. Hemizonid not seen.

Reproductive tract with single testis, short, usually extending part-way along pharyngeal gland but may not reach it; testis, seminal vesicle and vas deferens not clearly differentiated. Bursa apparently peloderan; smooth or crenate; may be prominent or obscure; arises 40 – 50% along length of body. Spicules paired, arcuate at about half length; moderately sclerotised; manubrium similar to or wider than shaft, not offset; blade narrows gradually to bluntly rounded tip with concavity on distal edge; opening sub-terminal. Inconspicuous muscles associated with cloaca. Tail arcuate, ventrally concave, conoid; length 1.3–3.0 times diameter at cloaca; broadly rounded tip.

Molecular phylogenetic relationships. With SSU, the blastn search of Fergusobia decorae n. sp. (V 462) ( FJ393271 , 1686 bp sequenced) revealed the highest matches were with V 470 ( EF 011672 ) ( F. tolgarae ), V 359 ( EF 011665 ) ( F. pohutukawa ) and V 410 ( FJ393268 ) ( F. armillarisae n. sp.) with 8–10 bp differences (99% identity). Sequencing of D2/D3 was not successful. With COI, F. d ec o r a e n. sp. (V 462) ( FJ386982 , 618 bp sequenced) had the highest match with V 405 ( FJ386964 ) ( F. armillarisae n. sp.) with 52 bp differences (92% identity).

Diagnosis and relationships. Fergusobia decorae n. sp. is morphologically characterized by the combination of a small, barely arcuate relatively slender parthenogenetic female with a short conoid tail with a broadly rounded tip; an arcuate, relatively broad, infective female with a broadly rounded tail tip; and a straight to arcuate male with a strong arcuate to angular spicule and a bursa which may be crenate arising at 30%–50% of body length.

Morphologically, Fergusobia decorae n. sp. is similar to F. pohutukawa , F. jambophila , F. tolgarae , F. cajuputiae , F. nervosae and F. sporangae . However, the cuticle of the parthenogenetic females does not swell on fixation as in F. pohutukawa and F. jambophila ; the shape of the heat relaxed parthenogenetic females is less curved than in F. cajuputiae and F. nervosae ; and they lack the broad opening of the stylet aperture present in F. sporangae . The male of F. decorae n. sp. has a flattened circum-oral area, differing from that of F. tolgarae , in which it is raised.

Parthenogenetic females of F. decorae n. sp. (arcuate shape) differ from F. brevicauda , F. brittenae , F. curriei , F. cosmophyllae , F. delegatensae , 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. tumifaciens , F. viminalisae , and F. viridiflorae (C-shape). In length (205–302 µm), they are shorter than parthenogenetic females of F. rileyi (310–394 µm). In having cuticle which does not swell upon fixation; they differ from F. linariifoliae n. sp., in which it does. The stylet (7–9 µm) of these parthenogenetic females is longer than in F. juliae (5–7 µm); and shorter than in F. camaldulensae (11–13 µm) and F. schmidti (11–14 µm). In having enormous oesophageal glands (b’ 1.5–3.0), they are similar to F. quinquenerviae but lack the extra lobe or flex found in glands of the latter. In having a body behind the vulva that narrows gradually, is arcuate and conoid in shape, with a broadly rounded tip, parthenogenetic females of F. decorae n. sp. differ from F. dealbatae , F. eugenioidae , and F. philippinensis (more slender, shape arcuate to straight). In length (13–25 µm, mean 16 µm), their tail is usually shorter than in F. tolgarae (mean 22 µm, range 18–25 µm). Fergusobia decorae n. sp. has a smooth quadricolumella, but it is not smooth in F. leucadendrae . Morphologically, parthenogenetic females of F. decorae n. sp. cannot be separated from F. fisheri , but the former tends to have a longer tail (13–25 µm, mean 16 µm vs 13–16 µm, mean 14 µm) and a slimmer body (a 8–11, mean 9.5 vs 6–8.5, mean 6.8). Similarly, it cannot be clearly separated from F. colbrani , but the latter tends to be more curved in shape when heat-killed.

The infective female of F. decorae n. sp. (arcuate) differs in shape from that of F. fasciculosae , F. gomphocephalae and F. nervosae (open C-shape). In length (207–256 µm), it is smaller than females of F. brittenae (375–550), F. colbrani (369–405 µm), F. cosmophyllae (374–448 µm), F. dealbatae (307–347 µm), F. eugenioidae (438 µm), F. fasciculosae (268–332 µm), F. floribundae (357–450 µm), F. juliae (396–550 µm), F. leucadendrae (270–291 µm), F. magna (537–633 µm), F. minimus (419–458 µm), F. morrisae (322–395 µm), F. pimpamensis (369-443 µm), F. philippinensis (290–370 µm), F. planchonianae (303-339 µm), F. porosae (277–300 µm), F. ptychocarpae (387–471 µm), F. sporangae (289–353 µm), and F. viminalisae (334–437 µm). This infective female has a short conoid tail (13–18 µm) with a bluntly rounded tip, separating it from F. armillarisae n. sp., F. camaldulensae , F. curriei , F. delegatensae , F. fisheri , F. leucoxylonae , F. microcarpae , and F. rosettae (almost hemispherical tail tip), and from F. brevicauda , F. diversifoliae , F. linariifoliae n. sp., F. quinquenerviae , F. rileyi , and F. tolgarae in which the tail is longer (respectively, 24–30, 23–39, 29–30, 20–29, 40–50, and 22–25 µm). It is not possible morphologically to separate the infective female of F. decorae n. sp. and F. cajuputiae or F. schmidti . It seems that F. viridiflorae (321 µm long) has a larger infective female than F. decorae n. sp. but only one specimen has been examined.

In shape (straight to arcuate), the male of F. decorae n. sp. differs from those of F. brittenae , F. curriei , and F. fasciculosae (J-shape), F. pimpamensis (J or C-shape), F. juliae , F. magna , F. planchonianae , F. ptychocarpae , and F. viridiflorae (with strongly curved posterior). In length (205–287 µm), it is smaller than that of F. brevicauda (330–420 µm), F. camaldulensae (383–451 µm), F. c o l b r an i (288–481 µm), F. delegatensae (350–518 µm), F. diversifoliae (413–459 µm), F. eugenioidae (341–420 µm), F. floribundae (403–570 µm), F. linariifoliae n. sp. (360–440 µm), F. minimus (368–502 µm), F. morrisae (347–413 µm), F. pohutukawa (398–469 µm), and F. rileyi (378–508 µm). In length (7–9 µm), the stylet is shorter than in F. leucoxylonae (10–13 µm). The male of F. decorae n. sp. has a flattened circum-oral area, differing from that of F. jambophila , and F. ro s e t t ae, in which it is raised. The shape of the tail (arcuate, conoid, with a broadly rounded tip) differs from that of F. philippinensis (truncate tip) and from F. leucadendrae (bluntly rounded tip). Spicule length (15–17 µm) is shorter than in F. dealbatae (18–22 µm), F. quinquenerviae (16–20 µm), F. schmidti (19–25 µm), and F. sporangae (17–25 µm). The shape of the spicule is arcuate, and differs from that in F. gomphocephalae , F. microcarpae , F. nervosae , F. tumifaciens , and F. viminalisae , in which it is more angular. The bursa of the F. d ec o r a e n. sp. male arises at ~ 30%–50% of body length, differing from F. cosmophyllae , F. fisheri , F. porosae , and F. tumifaciens in which the bursa is shorter (respectively, 12%–39%, ~ 20%, 15%–33%, and 18%–22%) and from F. armillarisae n. sp., F. cajuputiae , F. linariifoliae n. sp., and F. jambophila in which it is longer (>50%).

Etymology. Named after M. decora , the plant species from which the nematodes were collected.

Figures

FIGURE 2. Fergusobia decorae n. sp. (all in lateral view): A, Entire parthenogenetic female; B, Head of parthenogenetic female; C, Habitus; D, Tails of parthenogenetic females; E, Entire infective female; F, Head of infective female; G; Habitus; H, Tails of infective females; I, Entire male; J, Head of male; K, Habitus; L, Tails of males. Scale bars: A, E, I = 50 Μm. B, F, J = 5 Μm. Tails not drawn to scale.

FIGURE 4. Spicules from Fergusobia spp. collected from galls on narrow-leaved Melaleuca spp.: A, from M. armillaris; B, from M. decora; C, from M. linariifolia. Scale bar = 5 µm.

Tables

TABLE 3. Measurements (µm) of Fergusobia decorae n. sp. from Melaleuca decora. (Mean ± standard deviation, with range in brackets).

N	19	26	5
Length 302	260±24 (205–302)	267±18.5 (205–287)	229±23.4 (207–256)
a 11.3	9.5±1.0 (8.0–11.3)	10.7±0.9 (9.3–13.5)	9.7±1.7 (8.3–12.0)
b’ 3.0	2.0±0.4 (1.5–3.0)	2.3±0.3 (1.7–3.1)	2.5±0.7 (1.7–3.3)
c 12.1	16.5±3.0 (12.0–21.0)	9.0±0.9 (7.7–11.6)	16.2±1.0 (14.4–20.1)
c’ 1.6	1.4±0.2 (1.1–1.9)	2.2±0.3 (1.3–3.3)	1.0±0.2 (0.9–1.4)
V or T% 84	85.6±1.8 (81–88)	56.9±11.5 (27–75)	84.6±1.4 (83–87)
Body diameter 27	27±1.6 (25–30)	25±2.0 (21–29)	24±1.6 (21–25)
Stylet length 8	8±0.5 (7–9)	8±0.5 (7–9)	7±0.3 (7–8)
Ant. end to SE pore 84	74±8.8 (52–85)	76±10.0 (53–89)	67 (61–73)
Spicule length		16.2±0.7 (15–17)
Tail length	16±3.7 (13–25)	30±3.9 (18–36)	14±2.2 (13–18)