Eotetranychus fraxini

Migeon, Alain, Malagnini, Valeria, Navajas, Maria & Duso, Carlo, 2007, Notes on the genus Eotetranychus (Acari: Tetranychidae) in Italy and France with a redescription of Eotetranychus fraxini Reck, new record for Italy and Western Europe, Zootaxa 1509, pp. 51-60 : 55-59

Redescription of Eotetranychus fraxini

Reck (1948a) described a new Schizotetranychus , and classified it into the subgenus Eotetranychus . Although the original description from Reck was rather imprecise, the provided shape of the aedeagus and the peritreme allowed us to identify our specimens from northern Italy as E. fraxini . This species is here redescribed, including all the measurements and morphological characters currently used

Schizotetranychus (Eotetranychus) fraxini ( Reck, 1948a) : 448, figures 2 and 11; ( Reck, 1948b): 374, figures 6, 17 and 31.

Schizotetranychus fraxini Reck 1948 : ( Bagdasarian, 1957): 124, figure 54; ( Reck, 1959): 56, figure 82; ( Ripka et al., 1993): 562.

Diagnosis. Eotetranychus fraxini can be distinguished from other Eotetranychus species by considering the shape of the male aedeagus and the short tarsus I.

Female (Figs 1 and 3)

Four specimens where measured and the results are presented in Table 2 .

Idiosoma (Fig. 1A): Length 248 μm, width 156 μm.

Gnathosoma: Palptarsus spinneret about three times as long as broad, sensilium shorter than the nearby setae (Fig. 1D). Peritreme bulbous distally (Fig. 1C). Stylophore rounded anteriorly.

Dorsum: Dorsal striae with minute lobes about as long as wide, longitudinal on prodorsum and transverse on opisthosoma. All body setae linear, lanceolate. Dorsal setae extending beyond the base of next row (Fig. 1A). The measurements of the dorsal setae are given in table 2.

Venter: Ventral striae transverse. Genital flap with transverse striae, area anterior to genital flap with transverse striae (Fig. 1B).

Legs: Empodia split into two claw-like structures, each one split near the middle into three pairs of hairs (Fig. 1E). Tarsus I short, about 2–2.5 time long as wide, distal duplex setae with sensory seta about 4.5 times longer than tactile seta ( Fig. 3 A). Chaetotaxy as follows (numbers of setae refer to tactile setae; sensory setae are given in parentheses and duplexes setae – 1 sensory coupled with 1 tactile – counted separately) – coxa, trochanter, femur, genu, tibia, tarsus:

I: 2, 1, 10, 5, 8 + (2), 13 + (2) + 2 duplexes ( Fig. 3 A)

II: 2, 1, 7, 5, 8, 13 + (1) + 1 duplex ( Fig. 3 B)

III: 1, 2, 4, 4, 6, 10

IV: 1, 1, 4, 4, 7, 10

Male ( Figs 2 and 4 )

Four specimens where measured and the results are presented in Table 2 . Some measurements could not be taken on all the specimens, because the male was laterally oriented, which is essential to examine the aedeagus.

Males are slightly smaller than females.

Idiosoma: Length 232 μm, width 108 μm.

Gnathosoma: Palptarsus spinneret about four times as long as broad, sensilium about as long as the nearby setae ( Fig. 2 A). Peritreme bulbous distally. Stylophore rounded anteriorly.

Dorsum: Striae as for the female. Setae as for the female. Measurements are given in table 2.

Venter: All striae transverse as for the female.

Legs: Empodia I split into two claw-like structures, each one with a central spur and two smaller ones ( Fig. 2 C). Empodia II to IV with three pairs of hairs like as in female ( Fig. 2 D). Tarsus I short, about 2 –2.5 time long as wide, distal duplex setae with sensory seta about 5.3 times longer than tactile seta ( Fig. 4 A). Chaetotaxy as follows (numbers of setae refer to tactile setae, sensory setae are given in parentheses): I: 2, 1, 10, 5, 8 + (3), 13 + (3) + 2 duplex ( Fig. 4 A)

Material examined. Colli-Euganei, Rocca Pendice (Padova), Italia, on Fraxinus ornus (Oleaceae) , 10 July 2001, 3 males and 3 females, 5 October 2001, 2 males and 2 females, V. Malagnini leg. . Previous records. Georgia (Tbilissi) and Hungary (Ujlak) respectively on Fraxinus excelsior and Fraxinus sp. .

Remarks. Reck (1948a) recorded a total of 18 setae on male tarsus I, 14 on male tarsus II and 10 on male tibia I. We detected instead 20, 16 and 11 respectively on our specimens. This variation could be due to the lack of one or two proximal ventral setae on tarsus I, as observed on some of the specimens studied here. Eotetranychus fraxini is characterised by a female genital flap with transverse striae, which is typical of the willamettei group of the genus Eotetranychus . It also possesses eight tactile setae on the female tibia II like the species of the tiliarium group. The most characteristic feature for both male and female is the shortness of the tarsus I, having length/width values of 2–2.5 instead of 3–3.5 for most of the species.

The discovery of this species in Northern Italy, suggests a wider distribution of E. fraxini from Georgia to Western Europe, which could match to the distribution of the host plant genus, which includes the entire Holarctic region.

Figures

FIGURE 2. Eotetranychus fraxini Reck, male: (A) dorsal view of the right palpetarsus; (B) lateral view of three adeagus; (C) lateral view of the empodium of the first leg; (D) lateral view of the empodium of the second leg. Scale bar: 10 μm.

FIGURE 3. Eotetranychus fraxini Reck, female: (A) lateral view of the tarsus and tibia of the first leg; (B) lateral view of the tarsus and tibia of the second leg. Scale bar: 10 μm.

FIGURE 4. Eotetranychus fraxini Reck, male: (A) lateral view of the tarsus and tibia of the first leg; (B) lateral view of the tarsus and tibia of the second leg. Scale bar: 10 μm.

Tables

TABLE 2. Measurements of Eotetranychus fraxini Reck, habitus, dorsal setae and distances between the base of the dorsal setae (all values are in μm).

	Female (n=4)		Male
	Mean Minimum	Maximum	Mean	Minimum Maximum Number
Idiosoma:
length	248 230	260	232	220 250 4
width	156 140	190	108	105 110 2
Dorsal setae:
v2	48 44	52	35	33 36 3
sc1	84 81	88	68	66 69 3
sc2	55 50	64	44	41 46 3
c1	69 68	71	55	50 60 3
d1	72 70	74	57	55 58 3
e1	70 65	76	50	49 50 3
f1	68 61	75	46	42 50 3
h1	52 46	60	26	26 26 3
c2	74 71	78	55	55 55 3
d2	72 69	76	61	60 61 3
e2	73 70	78	52	52 52 2
f2	51 39	63	36	33 38 3
c3	61 53	71	43	43 43 2
Distances:
v2–h1	227 218	232	158	155 160 3
sc2–sc2	131 127	140	54	- - 1
c1–c1	46 40	49	47	- - 1