Eriocaenus equiseti ( Farkas, 1960 )

Petanović, Radmila U., Amrine Jr, James W., Chetverikov, Philipp E. & Cvrković, Tatjana K., 2015, Eriocaenus (Acari: Trombidiformes: Eriophyoidea), a new genus from Equisetum spp. (Equisetaceae): morphological and molecular delimitation of two morphologically similar species, Zootaxa 4013 (1), pp. 51-66 : 60-64

Eriocaenus equiseti ( Farkas, 1960)

( Figs. 4 D, 5A–D, 7 & 8)

Aceria equiseti Farkas, 1960: 316 –318, 317 ( Figs. 4–7 ) Eriophyes equiseti ( Farkas, 1960) : Farkas, 1965

Female (n=10). Body wormlike 213–374, 50–65 wide, white in colour. Gnathosoma 21–25, downcurved, dorsal pedipalp genual setae d 10–17, palpcoxal setae ep 3–5, apical setae v 1–3, cheliceral stylets 17–24. Prodorsal shield 30–34, 35–50 wide. Posterior part semi-elliptic, anterior half triangular, with pointed short lobe over gnathosoma. Prodorsal shield tubercles ahead of rear shield margin 15–18 apart, scapular setae sc 1–3, directed upward and slightly forward. Shield provided with numerous granules; some appear aligned in central part of shield between scapular tubercles, forming median, admedian and submedian lines; lateral fields covered with granules, irregularly distributed. Legs with all usual segments and setae. Leg I 38–45; femur 10–12, basiventral femoral setae bv absent; genu 5–8, antaxial genual setae l" 37–45; tibia 9–12, paraxial tibial setae l' 2–4; tarsus 7– 10, paraxial fastigial tarsal setae ft' 11–18, antaxial fastigial tarsal setae ft" 21–33, ventromesal seta u ′ 2–4; tarsal solenidion ω 6–8, rod-like, distally rounded; tarsal empodium 6–8, 5-rayed. Leg II 34–38; femur 7–12, basiventral femoral setae bv absent; genu 5–7, antaxial genual setae l" 17–23; tibia 7–9; tarsus 7–10, paraxial fastigial tarsal setae ft' 9–12, antaxial fastigial tarsal setae ft" 19–30, ventromesal seta u ′ 3; tarsal solenidion ω 6–8, rod-like, distally rounded; tarsal empodium 7–13, 5-rayed. Coxigenital area with 6–9 coxigenital annuli. Coxae with a pattern of numerous dashes; prosternal apodeme indistinct; subcapitular plate subtrectangular, anteriorly rounded; anterolateral setae on coxisternum I 1 b 4–9, 13–17 apart; proximal setae on coxisternum I 1a 9–23, 9–12 apart; proximal setae on coxisternum II 2 a 40–60, 24–31 apart. External genitalia 12–16, 20–24 wide, genital coverflap with 11–16 longitudinal striae in a single row, some striae sinuous; proximal setae on coxisternum III 3a 9–12, 13– 18 apart. Spermathecal apparatus similar to that described above for Eriocaenus ramosissimi . Opisthosoma with subequal annuli, 100–135 dorsal and 95–118 ventral annuli. Annuli with rounded microtubercles. Setae c2 35–43, 47–62 apart, on annulus 14–16; setae d 30–65, 34–46 apart, on annulus 31–41; setae e 2–4, 19–30 apart, on annulus 50–66; setae f 48–62, 32–38 apart, on annulus 84–104; setae h2 79–108, 11–13 apart; setae h1 3–6, 6–9 apart.

Male (n=3). Body wormlike, 190–215, 57–60 wide. Gnathosoma 22–25, palp coxal setae ep 2, apical setae v 2, dorsal pedipalp genual setae d 9–13, cheliceral stylets 18–22. Prodorsal shield shape and design similar to female, 30–31, 34–38 wide. Prodorsal shield tubercles ahead of rear shield margin, 15–16 apart, scapular setae, sc 1, directed upward and slightly forward. Leg I 30–34; femur 7–8, basiventral femoral setae bv absent; genu 5–6, antaxial genual setae l" 31–35; tibia 6–7, paraxial tibial setae l' 3–3; tarsus 7, paraxial fastigial tarsal setae ft' 19–16, antaxial fastigial tarsal setae ft" 17–23; ventromesal seta u ′ 3–4, tarsal solenidion ω 7–8, distally rounded; tarsal empodium 6, 5-rayed. Leg II 27–31; femur 6–7, bv absent; genu 5–6, l" 15–19; tibia 5–6; tarsus 6, paraxial fastigial tarsal setae ft' 6, ft" 17–22; ventromesal seta u ′ 2–3, tarsal solenidion ω 7, distally rounded; tarsal empodium 5–6, 5-rayed. Coxigenital area 7–11 coxigenital annuli, similar to female. Anterolateral setae on coxisternum I 1 b 4–9, 13–15 apart; proximal setae on coxisternum I 1a 13–16, 9–10 apart; proximal setae on coxisternum II 2a 29–48, 22–27 apart. Genitalia 17–18 wide, proximal setae on coxisternum III 3a 5 –8, 14–17 apart. Opisthosoma with subequal annuli: 82–97 dorsal and 83–94 ventral annuli. Annuli with microtubercles similar to female. Setae c 2 24–30, 41–46 apart, on annulus 13; setae d 30–43, 36 apart, on annulus 26–28; setae e 2, 23–24 apart, on annulus 42–48; setae f 40–44, 30–33 apart, on annulus 71–85; setae h2 73–84, 10–12 apart; setae h1 4, 6–8 apart.

Nymph (n=4). Body wormlike 135–216, 44–59 wide. Gnathosoma 15–21, downcurved, palpcoxal setae ep 3–4, dorsal pedipalp genual setae d 5–6, cheliceral stylets 14–20. Prodorsal shield shape and design similar to adult female, 28–30, 31–35 wide. Scapular setae sc 1–2, 11–16 apart directed upward and slightly forward. Leg I 22–30; femur 6–8, basiventral femoral setae bv absent; genu 3–5, antaxial genual setae l" 22–24; tibia 4-5; paraxial tibial setae l ′ 3 tarsus 4–5, paraxial fastigial tarsal setae ft' 13, antaxial fastigial tarsal setae ft" 17–19; ventromesal seta u’ 2, tarsal solenidion (ω) 5, distally rounded, tarsal empodium 5, 4–5-rayed. Leg II 21–26; femur 5–7, basiventral femoral setae bv absent; genu 3–4; antaxial genual setae l" 11–13; tibia 4–5; tarsus 4–5, paraxial fastigial tarsal setae ft' 11, antaxial fastigial tarsal setae ft" 11–14; tarsal solenidion ω 5–6, distally rounded; tarsal empodium 4–5, 4–5-rayed. Coxigenital area with 17–21 coxigenital annuli. Anterolateral setae on coxisternum I 1 b 2–3, 8–14 apart; proximal setae on coxisternum I 1a 5 –6, 8–10 apart; proximal setae on coxisternum II 2a 19– 34, 20–23 apart. Proximal setae on coxisternum III 3a 2 –4, 6–9 apart. Opisthosoma with 102–110 dorsal annuli, 90–100 ventral annuli. Setae c 2 17–21, 37–44 apart, on annulus 14–19; setae d 23–26, 28–35 apart, on annulus 33– 39; setae e 1,16–22 apart, on annulus 51–66; setae f 20–34, 24–28 apart, on annulus 81–90; setae h2 33–50, 10–11 apart; setae h1 2–3, 5–7 apart.

Larva (n=3). Body wormlike 78–147, 40–47 wide. Gnathosoma 16–17, downcurved, cheliceral stylets 13– 15. Prodorsal shield shape and design similar to adult female, 21–23, 17–20 wide. Scapular setae sc minute, 14 apart. Leg I 19–20; femur 4, basiventral femoral setae bv absent; genu 3; antaxial genual setae l" 16, tibia 3; tarsus 3; tarsal solenidion 3, distally rounded, tarsal empodium 3, 4-rayed. Leg II 16–19; femur 4, basiventral femoral setae bv absent; genu 2–3, antaxial genual setae l" 7–10; tibia 3; tarsus 2, paraxial fastigial tarsal setae ft' 3, antaxial fastigial tarsal setae ft" 7; tarsal solenidion ω 4, distally rounded; tarsal empodium 4, 4-rayed. Coxigenital area with 21 coxigenital annuli. Anterolateral setae on coxisternum I 1 b 6–12 apart; proximal setae on coxisternum I 1a 2, 7–8 apart; proximal setae on coxisternum II 2a 11–13, 18–19 apart. Proximal setae on coxisternum III 3a 1, 5 apart. Opisthosoma with 83 dorsal and 74–75 ventral annuli. Setae c 2 7–8, 33–35 apart, on annulus 18; setae d 4– 9, 22–26 apart, on annulus 31; setae e minute, 18–21 apart, on annulus 44; setae f 19–24 apart, on annulus 64; setae h 2 23–26, 8–9 apart; setae h1 2, 5 apart.

Material examined. All specimens collected in Serbia. Two females on microscope slides: #T245/1 and #T245/2, collected from Equisetum arvense (Equisetaceae) , Mitrovac, Tara mountain (43o55'08.8"N, 19o28' 26.5"E, elevation 1096 m) by M. Andjelković and R. Petanović on 21 September 2013; one female on slide #T246/ 1 collected from Equisetum telmateia, Bioska (43o51'48.2"N, 19o39'30.6"E, 654 m) on 18 September 2013 by M. Andjelković and R. Petanović. Six males and three females on slides #480/1–7, collected from E. telmateia, Mt. Goč-Gvozdac, Dobre vode (43o33'29.3"N, 20o44'56.5"E, elevation 860 m) on 29 June 2013 by M. Andjelković; 25 females on slides # 1421/1–3, 5–8, 10–23, 25, 26, 34, 35; 3 males on slides #1421/28–30; 3 nymphs on slides #1421/9, 26, 31 and 1 larva on slide #1421/32 collected from E. arvense, Dići on 5 July 2013 by D. Smiljanić and R. Petanović; 5 females on slides #1440 /1–5; 16 males, 5 nymphs and 3 larvae on slides #1440/6–22 collected from E. arvense, Dići on 18 September 2013 by M. Andjelković and R. Petanović; 5 females on slides #1428/1–5 collected from E. telmateia, Monastery Velika Remeta, Mt. Fruška Gora on 28 August 2013 by M. Andjelković. All above mentioned slides are deposited in the Department of Entomology and Agricultural Zoology, Faculty of Agriculture, University of Belgrade, Serbia. One female, 3 nymphs and 1 larva (on slide #1421/a) are deposited in the Acarological Collection of the Zoological Institute of the Russian Academy of Sciences ( ZIN RAS). In addition, four type specimens of Aceria equiseti Farkas, 1960 were examined from the Hungarian Natural History Museum, Department of Zoology, Budapest, Hungary, on microscope slides # HNHM Erioph-753, 754(Hp/B), 755 and 756, collected ex Equisetum arvense L. by H. Farkas at Börzsöny-Gyöngye, Hungary on 24.VII 1959.

Relation to plant host. The mites collected from Serbia were found living under scale-like leaves which were joined together to form a special envelope or “ohrea”. Browning or russeting of these plant parts were observed. The symptoms were probably noticed because of the dense colony of mites present. In the original description, damage symptoms were not specified. Perhaps this may have been because of a low number of mites. More than likely the same damage symptoms could be found in Hungary.

Differential diagnosis and remarks. The new mite species, E. ramosissimi is morphologically very similar to E. equiseti ( Farkas, 1960) and it is not easy to separate them according to qualitative morphological characters. However, they can be distinguished based on the number of rays on the empodia (7-rayed in E. ramosissimi and 5- rayed in E. equiseti ) and measurements of selected characters such as: body length; number of annuli in the coxisternal area; length of Leg I and Leg II, length of antaxial genual setae l" on Leg II, length of tibia+tarsus I, length of tibia+tarsus II, length of setae c2 and length of setae d ( Table 1 ). Selected characters were compared using the holotype female of E. ramosissimi alongside ranges of measurements of individual females of E. equiseti ( Farkas, 1960) (type specimens examined for this paper) and the original description by Farkas (1960). Two characters, i.e. the number of annuli in the coxisternal area and the length of antaxial genual setae l" on Leg II, which were not measured by Farkas (1960) for the original description of E. equiseti , were obtained herein from the type specimens borrowed from Hungarian Natural History Museum. In addition, both species inhabit different host plants belonging to two different plant subgenera, i.e. E. arvense and E. telmateia belong to the subgenus Equisetum L., but E. ramosissimum belongs to the subgenus Hippocheate (Milde) Baker.

Molecular differences. Sequencing yielded a 1032 bp long fragment of the 28S rDNA, including the D2 region. The sequence analyses showed diagnostic differences between the type species E. equiseti and the new species, E. ramosissimi . It is known from the literature that the levels of D 2 28S rDNA differentiation between morphologically similar mite species ranged from 0.2–2.1% for the host-associated wheat curl mite, Aceria tosichella ( Skoracka et al. 2013) . A mean sequence divergence for cryptic species within hazelnut bud mite, Phytoptus avellanae s.l., was 3.5%, while for stream and lake populations of the water mite species, Hygrobates nigromaculatus , D2 sequence differentiation was 7.5% ( Martin et al. 2010). In accordance with D2 sequence divergence of other mite species, the average pairwise genetic distance between E. ramosissimi and E. equiseti was 4%. The sequences differed in 48 nucleotide positions, including 7 bp insertions in the E. equiseti sequence. A high level of nucleotide substitutions in nuclear ribosomal sequences supports the conclusion made by morphological observations, that E. ramosissimi and E. equiseti are two different species.

* New measurements obtained from E. equiseti type specimens (borrowed from the Hungarian Natural History Museum).

Figures

FIGURE 4. Eriocaenus ramosissimi n. sp. (DIC images): A. Dorsal view of whole mite; B. Dorsal view of anterior section; C. Anterior section of male, ventrally; E. Genital coverflap; F. Internal female genitalia; D. Genital coverflap of E. equiseti.

FIGURE 5. Eriocaenus equiseti (SEM), female: A. Dorsal view of anterior section; B. Epigynium; C. Tarsal empodium, Leg. I, lateral view; D. Tarsal empodium, Leg I dorsal aspect; F. E. ramosissimi n. sp., tarsal empodium Leg I.

FIGURE 6. Location of Eriocaenus ramosissimi n. sp. on Equisetum ramosissimum, showing a group of mites inside the scale-like leaves which are joined together to form a special envelope known as an “ ohrea.

FIGURE 7. Semi-schematic drawings of Eriocaenus equiseti (Farkas) female: AD. Antero-dorsal view; AL. Antero-lateral view; CG. Coxal-genital region; em. Empodium; GM. Genital region, male; IG. Internal genitalia, female; L 1. Leg I; LO. Lateral opisthosoma; PM. Postero-lateral mite (telosoma). Scale bar: 25 µm, (except for em = 5 µm).

Tables

TABLE 1. Morphological differences observed between specimens of Eriocaenus ramosissimi n. sp. and Eriocaenus equiseti (populations from Serbia and original description).

CHARACTER	E. ramosissimi n. sp.	E. equiseti (Farkas, 1960) (specimens from Serbia)	E.equiseti (Farkas, 1960) , (original description; type specimens from Hungary)
Number of rays on empodia	7	5	5
Number of annuli in coxisternal area	5 (4–7)	6–9	6*
Length of body	245 (219–274)	213–374	210
Length of Leg I	39 (27–42)	38–45	45
Length of Leg II	32 (27–36)	34–38	38
Length of antaxial genual setae l" on Leg II	14 (12–15)	17–23	20*
Length of tibia+tarsus I	15(13–17)	16–22	20
Length of tibia+tarsus II	13 (11–15)	14–19	16
Length of setae c2	20 (17–27)	35–43	40
Length of setae d	34 (21–51)	30–65	44