Aceria thalgi Knihinicki

Knihinicki, Danuta K., Mccarren, Kathryn L. & Scott, John K., 2009, A new species of Aceria (Acari: Eriophyidae) damaging sowthistles, Sonchus spp. (Asteraceae), in Australia with notes on Aceria sonchi (Nalepa, 1902), Zootaxa 2119, pp. 23-38 : 25-32

Aceria thalgi Knihinicki sp. n.

( Fig. 2 , 3 , 4 , 5 & 6 )

Description. FEMALE (Measurements of holotype and range of 10 paratypes). Figs. 2 , 3 and 4 (A & B). Body 265 (159–265), width 66 (52–68), vermiform in shape and whitish in colour. Gnathosoma 22 (19–23), obliquely down-curved. Antapical seta (d) 6 (5–8). Basal seta (ep) 2 (2, n=7). Chelicerae 21 (17–21, n=9); oral stylets 25 (24–27, n=4). Prodorsal shield 34 (31–34), 59 (47–60) wide with a small, triangular, anterior lobe, 3 (3–4). Prodorsal shield pattern elaborate, consisting of a prominent median line, mostly continuous (if not broken midway), faint proximally. Admedian lines distinctive and entire, commencing at rear shield margin and progressing up and throughout anterior lobe. Sub-median lines extending from just below anterior lobe at a slight angle before joining distally (about 2/3 of the way along) with lateral lines on either side forming a curved, bow-shaped design. The sub-median lines and bow-shaped lateral lines culminate with a crescent-shaped arch framing each of the dorsal tubercles about 10 μm above like an eyebrow. A series of short, transverse and longitudinal lines randomly positioned between the dorsal tubercles and the arches. An additional lateral line borne above the arches on either side forming an obtuse triangular-shaped cell positioned against the prominent bow-shaped lateral lines. About 3–4 mixed transverse and longitudinal lines, mostly short, lie inside this cell. Further series of shorter or longer lines positioned either transversely or longitudinally on the lateral areas of the shield with granules marking the extremities. Microtubercles present on the annuli directly laterad of the dorsal tubercles. Tubercles of setae (sc) on rear shield margin, 28 (23–28) apart; prodorsal seta (sc) 46 (38–50), diverging and projecting backwards. Legs: With all normal setae present. Leg I 31 (27–31; measured from base of trochanter); femur 9 (8–10), femoral seta (bv) 7 (7–11, n=9); genu 5 (5–6), genual seta (l ʺ) 30 (25–38); tibia 7 (6–7), tibial seta (l ΄) 9 (7–11); tarsus 7 (6–7), located 1/3 from dorsal base, lateral seta (ft ʺ) 28 (23–27), dorsal seta (ft ʹ) 15 (13–16, n=9), unguinal seta (u ΄) 6 (6–7, n=9), solenidion (ω) 9 (7–9), distally rounded but without knob; empodium (em) 9 (6–9), simple, 6 (6) rayed. Leg II 29 (26–29) (measured from base of trochanter); femur 9 (7–9), femoral seta (bv) 10 (9–11, n=9); genu 5 (5), genual seta (l ʺ) 12 (10–12, n=9); tibia 6 (5–6); tarsus 7 (6–7), lateral seta (ft ʺ) 22 (22–30), dorsal seta (ft ʹ) 8 (8, n=9), unguinal seta (u ΄) 7 (6–7), solenidion (ω) 10 (7–10), distally rounded but without knob; empodium (em) 8 (7–9), 6 (6) rayed. Coxae: Coxal seta I (1b) 11 (9–13), tubercles (1b) 11 (11–12) apart; coxal seta II (1a) 19 (16–25), tubercles (1a) 11 (8–10) apart; coxal seta III (2a) 47 (30–48), tubercles (2a) 28 (24–29) apart. Coxae I and II with short striations, often slightly longer on coxae I. Prosternal apodeme (sternal line) present, 8 (7–8), divided anteriorly. Coxigenital region as shown with 9 (9–10) microtuberculated annuli. Opisthosoma: Evenly arched, subequal dorso-ventrally. With 83 (68–77) dorsal annuli and 76 (58–68) ventral annuli. Microtubercles present on all dorsal annuli, elliptical, becoming sparser and smaller from about dorsal annulus 42 to the rear. Microtubercles also present on the ventral annuli but smaller and triangular (sharktooth like) in shape, becoming elongated at about the 10th ventral annulus from the rear. Lateral seta (c2) 30 (22–33), on annulus 5 (5) from genital rear margin; ventral seta I (d) 60 (41–64) on annulus 19 (17–19), tubercles (d) 46 (37–51) apart; ventral seta II (e) 20 (17–22) on annulus 38 (34–37), tubercles (e) 22 (19–28) apart; ventral seta III (f) 28 (21–28) on annulus 68 (51–62) or 8th (7–8th) annulus from the rear, tubercles (f) 22 (19–22) apart. Caudal seta (h2) 68 (55–68). Accessory seta (h1) 6 (4–6). Female genitalia: 17 (15–17) and 22 (21–23) wide. Epigynum (coverflap) with 13 (11–13) longitudinal striations, anterior margin with 4 (4) transverse lines of microtubercles; genital seta (3a) 30 (16–30); tubercles 17 (15–18) apart.

MALE (Measurements of range of 5 paratypes). Fig 3 and 4 (C & D). Smaller than female, body 174–202, 55–64 wide; Gnathosoma: 18–21. Antapical seta (d) 5–7, basal seta (ep) 2; chelicera 17–20; oral stylets 21–24 (n=3); obliquely down-curved. Prodorsal shield: 30–34, 48–60 wide with small lobe and design resembling female, sc 28–33, tubercles 22–27 apart. Legs: Leg I 27–29; femur 7–8, bv 7–9; genu 4–5, l ʺ 20–35; tibia 6–7, l ΄ 5–7; tarsus 6–7, ft ʺ 20–28, ft ΄ 10–13, u ΄ 5–6, solenidion (ω) 8–9; empodium (em) 7–8, 5–6 rayed. Leg II 25–27; femur 6–7, bv 7–9; genu 4–5, l ʺ 8–12; tibia 5–6; tarsus 7, ft ʺ 22–24, ft ΄ 7–8, u ΄ 5–6, solenidion (ω) 9; empodium (em) 7, 5– 6 rayed. Coxae: Coxal seta I (1b) 11–13, tubercles 10–11 apart; coxal seta II (1a) 15–20, tubercles 8–9 apart; coxal seta III (2a) 27–31, tubercles 20–24 apart. Coxae I and II with striations similar to female. Coxigenital region a shown with 8–9 microtuberculated annuli. Opisthosoma: Similar to female; evenly arched and subequal dorso-ventrally, with 65–70 dorsal annuli and 54–57 ventral annuli. Appearance of microtubercles on dorsal and ventral annuli similar to female. Lateral seta (c2) 22–32, on annulus 3–5 (from genitalia); ventral seta I (d) 40–54 on annulus 15, tubercles 34–39 apart; ventral seta II (e) 16–20 on annulus 28–31, tubercles 18–20 apart; ventral seta III (f) 20–26 on annulus 51–54 or 7th from the rear, tubercles 18–20 apart. Caudal seta (h2) 52–60. Accessory seta (h1) 4–5. Male genitalia: 18–19 wide and 10–13; Epiandrium ornamented with small granules, genital seta (3a) 17–30 and tubercles 14–16 apart.

NYMPH (Measurements of range of 2 specimens). Fig. 5 & 6 . 150–180, 55–60 wide; vermiform in shape, translucent and whitish in colour. Gnathosoma: 14–16. Antapical seta (d) 4; basal seta (ep) 2; chelicerae 17–18; oral stylets 19–22. Prodorsal shield: 29–30, 48–54 wide; semi-ovoid, anterior lobe very small. Ornamentation faint but resembling that of adult with similar arrangement of median, submedian, admedian and lateral lines; sc 30–36, tubercles 24–25 apart. Legs: Leg I 20–22; femur 5, bv 4–6; genu 3–4, l ʺ 20–21; tibia 4–5, l ΄ 5; tarsus 4–5, ft ʺ 18–22, ft ΄ 8–10, u ΄ 3–4, solenidion (ω) 6, distally rounded but without knob; empodium (em) 6, 5–6 rayed. Leg II 20–21; femur 6, bv 5–6; genu 3, l ʺ 7–9; tibia 4; tarsus 4–5, ft ʺ 18, ft ΄ 5, u ΄ 4, solenidion (ω) 6–7, distally rounded but without knob; empodium (em) 5, 5–6 rayed. Coxae: Coxal seta I (1b) 7, tubercles 10–12 apart; coxal seta II (1a) 10–16, tubercles 8 apart; coxal seta III (2a) 19–30, tubercles 20 apart. Coxae with fewer striations than adult. Prosternal apodeme present, 5 long, divided anteriorly. Coxigenital region (as shown Fig. 5 ) with 10–11 microtuberculated annuli. Genital seta (3a) 14– 15, tubercles 6–7 apart. Opisthosoma: Appearance of annuli similar to adult, evenly arched and subequal dorsoventrally. Microtubercles evenly present on all dorsal and ventral annuli but smaller and triangular in shape appearing more elongated from about the 10th ventral annulus from the rear. With 65–69 dorsal annuli and 57–59 ventral annuli. Lateral seta (c2) 17–20, on annulus 2 (from genital tubercles); ventral seta I (d) 30–35 on annulus 22–23, tubercles 30–38 apart; ventral seta II (e) 10–12 on annulus 34, tubercles 18–19 apart; ventral seta III (f) 19–21 on annulus 43–52 or 6–7th annulus from the rear, tubercles 20 apart. Caudal seta (h2) 45–50. Accessory seta (h1) 4.

LARVA. Not observed.

EGGS. Spherical. Translucent to creamy white in colour, with diameter measured 35–64 μm. Relatively large compared to adult. On the inside of leaf curls.

DEUTOGYNE FEMALE. Not observed.

Host plants. Sonchus asper (L.) Hill, S. hydrophilus Boulos and S. oleraceus L.: Asteraceae ; Tribe: Lactuceae and subtribe Sonchinae. Sonchus hydrophilus is native to Australia.

Relationship with host plants. Causing severe curling and rolling of leaf margins ( Fig. 7 ).

Type material. Holotype female (single specimen on microscope slide preparation) ex curled leaf edges of sowthistle, Sonchus oleraceus, Capel (south of Perth), W.A., S 33°39.559΄ E 115°43.063΄ coll. J.K. Scott, 28.i.2008. Deposited in ASCU. Paratypes on 28 microscope slide preparations (18 x preparations in ASCU and 10 x preparations in ANIC; some slides have multiple specimens) with same collection data as holotype. Additional paratypes are as follows (deposited in ASCU): WA: 2 x microscope slide preparations ex curled leaf edges of S. oleraceus Perry Lakes, Floreat, S 31°56.669΄, E 115°47.076΄ coll. K. McCarren, 17.xii.2006; 10 x microscope slide preparations ex S. hydrophilus , curled leaves, Star Swamp (north of Perth), S 31°51.364΄, E 115°45.501΄, K. McCarren, 18.i.2007; 1 x microscope slide preparation ex S. hydrophilus (2 separate plants), curled leaves rosette, Star Swamp, S 31°51.364΄, E 115°45.501΄ K. McCarren, 18.i.2007; QLD: 4 microscope slide preparations ex curled leaf edges of S. oleraceus , (Site 45), Crow’s Nest, S 27°15.931΄, E 152°03.454΄, coll. K. McCarren 23.vii.2007; NSW: 1 x microscope slide preparation ex curled leaf edges, S. oleraceus, Sydney , coll. Anonymous, 4.xi.1940 ( ASCT 00113292); 4 x microscope slide preparations ex Sonchus sp., curled leaves, Strathmore Lane, Molong, S 33°07.234΄ E 148°51.552΄, coll. M. Davison, 13.ii.2008.

Additional material examined. NSW: 1 x microscope slide preparation ex S. oleraceus , causing rolling of edges of milk thistle, Sydney, coll. Anonymous, 12.vii.1939 ( ASCT 00113296); 5 x microscope slide preparations ex S. oleraceus , curled leaf edges, Sydney, coll. Anonymous, 4.xi.1940 ( ASCT 00113290; ASCT 0013291; ASCT 00113293; ASCT 00113294; ASCT 00113295). WA: 1 x microscope preparation ex S. oleraceus, Site 14 #A1, Lake Goollelal, Kingsley, S 31°48.223΄, E 115°48.741΄, coll. K. McCarren, 16.i.2007; 1 x microscope preparation ex S. oleraceus, Site 15 #A4, near Myalup, S 33°07.259΄, E 115°43.363΄, coll. K. McCarren, 31.i.2007; 1 x microscope preparation (broken) ex S. oleraceus, Site 26 #A2, Tambellup, S 34°02.831΄, E 117°38.492΄, coll. K. McCarren, 1.ii.2007; 1 x microscope slide preparation (broken) ex S. hydrophilus , curled leaves, Star Swamp (north of Perth), S 31°51.531΄, E 115°45.501΄, K. McCarren, 18.i.2007; 1 x microscope slide preparation ex S. hydrophilus , curled rosette leaves, Star Swamp, S 31°51.531΄, E 115°45.501΄ K. McCarren, 18.i.2007.

Etymology. The species name thalgi is a word (gender unknown) for sowthistle in the traditional Ngarrindjeri language of the Lower Murray region of South Australia ( Clarke 2007). It is here used as a noun in apposition.

Diagnosis. The new species, Aceria thalgi , is close to Aceria sonchi ( Nalepa 1902) , however, there are several important differences. Aceria thalgi can be distinguished by the appearance of lines on the prodorsal shield and number of rays on the empodium (6-rayed in the new species as opposed to 5-rayed in A. sonchi ). The damage symptoms attributed to both species are disparate. In Italy ( Nalepa 1902, 1905) and northern Spain ( Liro & Roivainen 1951), A. sonchi was described as causing thick walled, irregular galls, 2-3 mm diameter, on the upper and lower surfaces of leaves with gall entry through a conical protuberance on the leaf upper surface. This is in stark contrast to the damage symptoms of severe curling and rolling of leaf edges caused by the new species on Sonchus species in Australia ( Fig. 7 ).

Figures

FIGURE 2. Aceria thalgi sp. n. D Dorsal view of female mite; V Ventral view of female showing genitalia and coxae.

FIGURE 3. Aceria thalgi sp. n. SA Lateral view of anterior region of female; ES Lateral view of dorsal and ventral annuli region. API Apodeme of internal female genitalia; GF Coxigenital region of female; GM Coxigenital region of male; L 1 Lateral view of Leg I; L 2 Lateral view of Leg II; E Tarsal empodium and solenidion.

FIGURE 5. Aceria thalgi sp. n. DNY Dorsal view of nymph; VNY Ventral view of nymph.

FIGURE 7. Damage symptoms by Aceria thalgi sp. n. showing leaf rolling and curling of A Sonchus oleraceus, B S. asper and C S. hydrophilus. D Enlarged image of diseased leaf of S. oleraceus. Flowerhead damage on E S. oleraceus and F S. asper. Scale bar = 5 mm.

FIGURE 4. A – D Light micrographs of Aceria thalgi sp. n. as viewed under 100 X oil immersion. A Prodorsal shield of female; B Coxigenital region of female; C Prodorsal shield of male; D Coxigenital region of male. Scale bar = 10 μm.

FIGURE 6. A – B Light micrographs of Aceria thalgi sp. n. nymph as viewed under 100 X oil immersion. A Prodorsal shield; B Coxigenital region. Scale bar = 10 μm.