Georgiobia skuthiae, Zhovnerchuk & Auger, 2019

Zhovnerchuk, Olga & Auger, Philippe, 2019, Spider mites (Acari: Tetranychidae) from the Black Sea Biosphere Reserve (Ukraine): faunistic survey, reinstatement of the genus Georgiobia Wainstein, 1960 and description of a new species, Zootaxa 4559 (2), pp. 321-338 : 325-332

Georgiobia skuthiae n. sp.

( Figures 1–6 )

Type material. Holotype (female), 1 female, 1 deutonymph and 1 protonymph paratypes from Agropyron sp. ( Poaceae ), steppe area of Ukraine, Kherson region, Gola Prystan district, Black Sea biosphere reserve, Solenoozerny (46°30’35’’N, 31°54’04’’E, 1 m a.s.l., flood plain), 08/06/2008, coll. S. Pogrebnyak. Holotype and paratypes deposited in the collection I.I. Schmalhausen Institute of Zoology of National Academy of Sciences of Ukraine (Kyiv, Ukraine).

Diagnosis (female). Leg I very long, twice as long as body length, about 1.5 mm, with tarsus almost retrorse distally. Tarsal tectal setae (tc ’- tc ’’) absent, first primiventral setae (pv ’) absent on tarsus I. Dorsal body setae slender, stout, serrate, inserted on quite strong, granulate, tubercles; inner setae far longer than longitudinal distance to base of setae next behind. Integument with medioprodorsal striations with geometric alveoli; medial striation of hysterosoma transverse, longitudinal to wrinkled between inner and lateral setae. Macrosetae on tibia III and IV as long as or slightly longer than tibia III and IV, respectively. Peritreme ending in a well-developed suboval shaped anastomosis, stylophore emarginate.

Description. Female. Body length 730 (720) including gnathosoma, width 413 (410), gnathosoma 160 (155), v 2 - h 1 535 (565), sc 2- sc 2 310 (290), c 3 - c 3 335 (340).

Dorsum. Medial propodosomal plate area with distinct regular polygonal reticulate pattern resembling geometric alveoli filled with fine irregularly punctate striae ( Fig. 1 A–B). Lateral striation longitudinal. Rest of idiosoma with medial striation transverse. Striation longitudinal to wrinkled-longitudinal between first three pairs of dorsocentral and lateral setae, areas with more obvious wrinkled striation between dorsocentrals and dorsolaterals of each of the first three rows. Transverse striation between setae e 1 and f 1, irregular and punctate caudally beyond setae f 1-2.

Prodorsum with three pairs of setae, hysterosoma with ten pairs. Humeral setae (c 3) not in lateral position, moved behind first dorsolateral setae c 2. Dorsal setae relatively long, linear lanceolate, serrate, inserted on strong tubercles. All dorsal tubercles punctate, finely granulated, cone shaped ( Fig. 1 C ); tubercles of members of d 1 and e 1 setae obviously contiguous.

First, second and third pairs of dorsocentral hysterosomal setae surpass insertions of consecutive setae, setae c 1 and d 1 the longest; setae v 2, c 2, c 3 and h 1 similar in length, the shortest. Setae lengths: v 2 92 (90); sc 1 123 (121); sc 2 105 (117); c 1 168 (135); c 2 90 (98); c 3 76 (97); d 1 160 (150); d 2 130 (122); e 1 150 (145); e 2 130 (130); f 1 125 (113); f 2 100 (107); h 1 80 (98). Distances between setae: c 1 - c 1 55 (50), d 1 - d 1 43 (38), e 1 - e 1 48 (45), c 1 - d 1 115 (120), d 1 - e 1 105 (140), e 1 - f 1. 100 (105). Sacral setae f 1 in normal position, in line with other dorsocentral setae, not contiguous with f 2 setae.

Gnathosoma. Stylophore rounded, slightly emarginate anteriorly, longer than wide 130 (125) long 80 (90) wide. Tibial claw of palpus slightly surpasses tip of palptarsus ( Fig. 3 D ). Palptarsus quite short with six setae and one solenidion. Eupathidia ul’ ζ, ul’’ ζ and solenidion subequal in length, su ζ longer about 6. Peritreme anastomosed distally in a suboval enlargement, length 32 (30), width 15 (13) ( Fig. 3 E ).

Venter. Striation transverse between 1 st (1a) and 2 nd (3a) pairs of setae, with irregular pattern medially, obliquelongitudinal laterally between 2 nd and 3 rd (4a) pairs of setae, transverse between members of 4a, transverse anterior to aggenital (ag) pair of setae, then longitudinal between ag setae ( Fig. 3F ). Sacculus of spermatheca not seen. Three pairs of pseudanal setae (ps 1-3) and two pairs of ventrocaudal (h 2-3) setae present.

Legs. Leg I about twice as long as body length, legs II to IV less than half the body length. Leg I 1615 (1515) long (measured from femur to tarsus), leg II 310 (315), leg III 275 (275), leg IV 335 (345). Length of segments of leg I as follows: trochanter 30 (24), femur 700 (680), genu 55 (55), tibia 640 (575), tarsus 220 (200). Tibia and tarsus I bow-shaped, the latter almost retrorse distally, both with ribbed aspect ( Fig. 2 A–B). Leg setal counts as follows ( Figs. 2 A–B, 3 A–C):

I 2 ¯ 1 ¯ 9 ¯ 2 – 13 + (1) – 11 + (1) + 2 duplexes;

II 2 ¯ 1 – 6 ¯ 2 –7 ¯ 11 + 1 duplex;

III 1 ¯ 1 – 2 – 3 ¯ 5 ¯ 8 + (1);

IV 1 ¯ 1 – 2 – 3 ¯ 5 – 8 + (1).

True claws and empodia pad-like, the latter with two rows of tenent hairs. Leg I empodial pad and pad-like true claws similar in length ( Fig. 2 C ); empodial pads II–IV about twice as long as true claw pads ( Fig. 2 D ).

Tarsi without tectal setae (tc ’- tc ’’), first primiventral setae (pv ’) absent on tarsus I, present on other tarsi. Tarsus I with two distal duplex setae inserted near each other. Solenidia members of duplex setae subequal, 92 and 91, tactile members also subequal, 6 and 5. On leg II, duplex solenidion 42 (44), tactile setae 8 (8). On tarsi III and IV solenidia 17 (18) and 11, respectively. Long, strong, stout, serrate seta present on tibia III and IV, far less developed on tibia II ( Fig 3 A–C). On tibia III, macroseta and leg segment subequal in length, 82 (80) and 82(79), respectively ( Fig. 3 B ); on tibia IV, macroseta slightly longer than respected segment, 101 (106) and 99 (95), respectively ( Fig. 3 C ). Tarsi III and IV with solenidion not associated with tactile (ft ’); solenidion III, 17 (18) about ¼ the length of tactiles, solenidion IV 11 about ½ the length of tactiles.

Proximal coxisternal seta 1b slender 56 (50), distal coxisternal seta 1c shorter 19 (21), serrate, stout ( Fig. 2E ).

Deutonymph (n=1), ( Fig. 4 ). Body length 500 including gnathosoma, width 290, gnathosoma 80, v 2 - h 1 400, sc 2- sc 2 215, c 3 - c 3 232.

Dorsum. Medial prodorsal striation resembling that of female, with geometric alveoli filled with fine irregular striae becoming punctate close to setae v 2, lateral striation longitudinal ( Fig. 4 B ). Overall hysterosomal striation pattern transverse between members of setae c 2 to f 2, longitudinal laterally. Humeral setae (c 3) not in lateral position, moved posterior to first dorsolateral setae c 2. Dorsal setae as in female, inserted on strong tubercles ( Figs. 4 A–C). Dorsal tubercles cone shaped with irregular striation punctate but not finely granulated ( Fig. 4 C ); tubercles of members of setae d 1, e 1 and of f 1 obviously contiguous. First, second and third pairs of dorsocentral hysterosomals much longer than distances between consecutive setae, setae c 1 and d 1 setae the longest while setae h 1 the shortest ( Fig. 4 A ). Setae lengths: v 2 82; sc 1 110; sc 2 114; c 1 154; c 2 104; c 3 96; d 1 146; d 2 122; e 1 134; e 2 108; f 1 108; f 2 94; h 1 66. Distances between setae: c 1 - d 1 60, d 1 - e 1 100, e 1 - f 1 80 (distances between members of c 1, d 1 and e 1 setae were not assessed because of the mounting effect and setal insertions on strong tubercles that caused large variations).

Gnathosoma. Peritreme anastomosed distally, 16 long ( Fig. 4D ).

Venter. Ventral striation transverse between 1 st (1a) and 2 nd (3a) pairs of setae, with irregular pattern between 2 nd and 3 rd (4a) pairs of setae and transverse from setae 4a to aggenital (ag) setae.

Legs. Leg I slightly shorter than body length, legs II to IV less than half the body length. Leg I 440 long (measured from femur to tarsus), leg II 172, leg III 176, leg IV 190. Length of segments of leg I as follows: femur 172, genu 32, tibia 144, tarsus 91. Leg setal counts as follows:

I 2 ¯ 1 ¯ 6 ¯ 2 – 9 + (1) – 9 + (1) + 2 duplexes;

II 2 ¯ 0 – 3 ¯ 2 –3 ¯ 7 + 1 duplex;

III 1 ¯ 1 – 2 – 2 ¯ 3 ¯ 6 + (1);

IV 1 ¯ 0 – 1 – 2 [1] ¯ 3 – 6.

True claws and empodia pad-like as in female. First primiventral setae (pv ’) absent on tarsus I, present on other tarsi. Tarsi without tectal setae (tc ’- tc ’’). Large strong serrate seta present on some leg segments ( Fig. 4A ), the longest on femur I, half the length on other segments: on femur I 120, on genu I 66 (twice as long as leg segment), on tibia III and IV 40 and 56 (slightly longer than leg segment), respectively. Tarsus III with short solenidion, about 1/3 the length of distal tactile setae.

Protonymph (n=1), ( Fig. 5 ). Body length 370 including gnathosoma, width 220, gnathosoma 70, v 2 - h 1 280, sc 2 153, c 3 – c 3 164.

Dorsum. Prodorsal striation longitudinal becoming punctate close to setae v 2, medial alveoli pattern almost absent (difficult to see), lateral striation longitudinal ( Fig. 5 B ). Overall hysterosomal striation pattern transverse between members of setae c 2 to f 2, longitudinal laterally. Humeral setae (c 3) not in lateral position, moved behind first dorsolateral setae c 2. Dorsal setae relatively long, linear lanceolate, serrate, inserted on strong tubercles ( Figs. 5 A, C ). Dorsal tubercles cone shaped with irregularly broken striation ( Fig. 5 C ). First, second and third pairs of dorsocentral hysterosomal setae surpass insertions of consecutive setae, setae c 1 the longest, setae h 1 the shortest ( Fig. 5 A ). Setae lengths: v 2 62; sc 1 80; sc 2 84; c 1 126; c 2 74; c 3 62; d 1 114; d 2 82; e 1 98; e 2 76; f 1 74; f 2 64; h 1 46. Distances between setae: c 1 - d 1 44, d 1 - e 1 64, e 1 - f 1 66 (distance between members of c 1, d 1 and e 1 setae were not assessed because of the mounting and setal insertions on strong tubercles that cause large variations).

Gnathosoma. Peritreme ending in a reduced anastomosis.

Venter. Ventral striation entirely transverse between 1 st (1a) and 3 rd (ag) pairs of ventral setae.

Legs. Leg I obviously shorter than body length, 224 long; legs II to IV about ¼ the body length: leg II 130, leg III 125, leg IV 135. Length of segments of leg I as follows: femur 80, genu 28, tibia 60, tarsus 56. Leg setal counts as follows:

I 2 ¯ 0 ¯ 3 ¯ 2 ¯ 5 + (1) – 5 + 2 duplexes;

II 1 ¯ 0 – 2 ¯ 2 –3 ¯ 7 + 1 duplex;

III 1 ¯ 0 – 2 – 1 ¯ 3 ¯ 6;

IV 0 ¯ 0 – 2 – 1 ¯ 3 – 6.

True claws and empodia as in deutonymph. First primiventral setae (pv’) absent on tarsus I, tarsi I to tarsi III without tectal setae (tc ’- tc ’’). Large strong serrate setae present on some leg segments, the longest on femur I, half the length on genu I and far smaller on tibia III and IV ( Fig. 5 A ): on femur I 108 (longer than leg segment), on genu I 48 (less than twice as long as leg segment), on tibia III and IV 18 and 24, respectively.

Male. Not known

Etymology. The specific epithet “skuthiae” refers to the old Greek name of the region located in the north of the black sea, ΣκΥΘΊα (= Scythia), the location were the new species was collected, meaning from Skuthia after latinisation.

Remarks. Initially we were reluctant to create a new species because of the similarities between the leg setal counts and that of the striation patterns of the medial part of the propodosoma found in G. skuthiae n. sp. and in G. shirakensis despite other obvious morphological differences. Following a careful search of the descriptions of other species belonging to the genus Georgiobia , particularly African ones, and after a comparison with some type specimens of G. shirakensis from Reck’s collection, we concluded that the Ukrainian specimens reported here constitute a new species.

Georgiobia skuthiae n. sp. and G. shirakensis have identical leg setal counts but the latter is also identical to G. crassata regarding this criterion. However, G. shirakensis and G. crassata clearly differ according to the size and shape of their dorsal setae. Moreover, G. skuthiae n. sp. and G. shirakensis are also very close to African species of Georgiobia according to the medial propodosomal striation pattern (geometrical alveoli pattern present). Therefore we concluded that both leg setal counts and medial prodorsal striation are too consistent for species separation in this genus, but other morphological traits can distinguish species of Georgiobia : here, the body size, the length of the forelegs, the length and the relative lengths of tibial macrosetae III and IV, the lengths of dorsal setae, and the shape of the stylophore are distinctive.

Body and leg I are longer in G. skuthiae n. sp. compared to G. shirakensis . These species can also be separated by the length of their dorsal setae: except for sacrals (f 1 and f 2) and clunals (h 1) which are subequal in length in both species, the dorsal body setae are obviously longer in G. skuthiae n. sp. (setae sc 2 more than ⅓ longer). Moreover, in G. skuthiae n. sp. the stout macrosetae present on tibia III and IV are about twice as long as in G. shirakensis (80 vs. 41); macrosetae are as long as tibia III and IV, vs. ½ and ¾ to ¼ the length, in G. skuthiae n. sp. and G. shirakensis , respectively. Finally, the stylophore is emarginated only in the new species.

The tarsal leg chaetotaxy of Georgiobia , as seen in G. skuthiae n. sp., is singular for two reasons: 1) the fundamental tectal setae (tc ’- tc ’’) are absent on all the tarsi ( Figs. 3 A–C). This type of setal reduction is not a real novelty as it is observed in the closely related genus Aplonobia and was previously reported by Wainstein (1958b) in three species of Georgiobia but also in other genera like Mesobryobia and Petrobia Murray, 1877 ; 2) in the distal part of the ventral side of tarsus I, one seta is missing and one is unpaired ( Fig. 2-A ). According to the possible location of this missing seta and by homology with the setal ontogeny of tarsi I and II, it seems that the setal reduction concerns a fundamental primiventral seta. Indeed, on the underside of tarsus I, the eupathidial seta usually not closely paired with pv ’’ and located near the level of the duplex setae is lacking ( Fig. 6 ). We conclude that the missing seta must be the seta pv ’.

Figures

FIGURE 1. Georgiobia skuthiae n. sp., female. A. dorsal aspect, B. detail of medial propodosomal striation, C. dorsal body seta (e 2). Scale bars = 100 µm (A), 10 µm (B), 25 µm (C).

FIGURE 2. Georgiobia skuthiae n. sp., female. A. tarsus I, B. tibia I, C. empodium and claws I, D. empodium and claws II, E. coxisternal setae 1b, 1c (from left to right). Scale bars = 25 µm (A–B), 10 µm (C–E).

FIGURE 3. Georgiobia skuthiae n. sp., female. A. tarsus and tibia II, B. tarsus and tibia III, C. tarsus and tibia IV, D. palptarsus and palptibia, E. peritremal enlargement, F. ventral striation. Scale bars = 25 µm (A–C), 10 µm (D–E), 50 µm (F).

FIGURE 4. Georgiobia skuthiae n. sp., Deutonymph. A. dorsal view, B. detail of prodorsal striation, C. tubercles striation, D. peritreme. Scale bars: 100 µm (A), 25 µm (B–D).

FIGURE 5. Georgiobia skuthiae n. sp., Protonymph. A. dorsal view, B. detail of prodorsal striation, C. tubercles striation. Scale bars: 50 µm (A), 25 µm (B, C)

FIGURE 6. Schematic representation of the underside of tarsi I and II showing setal insertions in the protonymphs, deutonymphs and adult female of Georgiobia skuthiae n. sp.