Mackiella reclinata Chetverikov, Craemer, Vishnyakov & Sukhareva, 2014, n. sp.

Mackiella reclinata n. sp. Chetverikov and Craemer

(Figs. 2–8, Tables 1, 3 & 4)

Description of external morphology. Female holotype. Idiosoma vermiform, whitish or pink, 218, 60 wide at the level of seta c2. Prodorsal shield subpentagonal-subcordate 41, 41 wide, with broad, thin frontal lobe (Figs. 2 A,E; 3A,B; 4A,B). Frontal lobe consists of roundish, subcordate apical part (Fig. 3 A b, 3B b) and subrectangular basal part (Fig. 3 A a, 3 B a), divided by lateral notch (Fig. 3 B d). Basal part 4, 16 wide; apical part 8, 12 wide. Large eyelike structures, partly surrounded by distinct, weakly tuberculate circular ridges, situated latero-posteriorly to tubercles of ve (Figs. 2 A; 4A,B c). Setae ve 8, directed anterolaterad, tubercles 26 apart; sc 12, directed up, tubercles 19 apart. Distance between tubercles of ve and sc 13. Shield ornamentation. Ridge-like median and admedian lines absent1. Weak outlines of indistinct longitudinal folds or wrinkles of cuticle can be seen in middle part of prodorsal shield on SEM images (Fig. 2 E, 2F, 3H). Two short submedian-I lines present in posterior 1/3 of prodorsal shield medial to tubercles of sc. Submedian-II line goes from rear shield margin laterally to tubercles of sc straight towards tubercles of ve. Submedian I and II lines accompanied by one–two slightly undulate striae. Small medioposterior fovea (“pit”) more or less distinctly discernable in all the studied females under CLSM an LM (Fig. 2 A; 4A,B).

1. Instead of ridge-like median and admedian lines present in many eriophyoids, the new species has 3-4 indistinct longitudinal indentations in the middle field of the prodorsal shield (vague under LM, better seen under SEM), which probably correspond to shallow cuticular apodemes separating bundles of extrinsic gnathosomal muscles of the chelicerae and the palpi.

Gnathosoma elongate, directed forward and slightly down, 23. Basal half of gnathosoma is covered by the frontal lobe (Fig. 3 B). Palpcoxal seta ep is clearly seen under CLSM and LM and presumably is placed on mesal surface of the palp, because during slide making procedures the palps usually move apart (Fig. 4 A,B). Basal segment of palp 10 wide with dense apodeme 6, left and right apodemes together form a “V” or “U”-like figure. Seta ep 1.5, palp genual seta d 5, seta v 1.5.

Leg I (Figs. 2 C, 3C) 32, tibia 7, l' 6, tibial solenidion φ 6; tarsus 6, ft' 3, ft ″ 11, u' 3, ω 8, without knob; empodium 7–8-rayed, 5. Leg II (Fig. 2 D,) 28, tibia 6, l', tarsus 5, ft' 3, ft ″ 18, u' 4, ω 7, without knob; empodium 7–8-rayed, 4 (4–5). Seta bv present on legs I–II. Femur I&II, genu I&II and tibia I&II distally with small spinules. Thin, distinct ridge present on ventral surface of femora I&II anterior to tubercle of seta bv (Fig. 2 C,D).

Coxisternal plates (Fig. 4 C,D) four shorter ridges between setae 1a, together vaguely forming a w-shape, and each plate with 2–4 thin, distinct ridges. Subcapitular plate ( Fig. 4 D e, 4E e, 4F e ) subtriangular, anteriorly rounded, with two thin longitudinal ridges (Figs. 4 E f, 4F f). Setae 1b 15, 11 apart; 1a 18, 11 apart; 2a 26, 27 apart. Prosternal apodeme indistinct; three complete and two incomplete coxigenital annuli anterior to epigynium.

External genitalia (Figs. 3 F, 4C,D,E). Genital coverflap oval-shaped, 12, 19 wide; putative rudimentary pregenital plate2 (sensu Chetverikov et al. 2014a, Figs. 6 C a, 6D a) situated anterior to basal genital coverflap (Fig. 3 F, coloured in yellow), setae 3a 13, 16 apart. Opisthosoma with 18 dorsal and 55 ventral annuli microtuberculated differently: dorsal annuli bear from 7–10 (anteriorly) to 1–3 (posteriorly) longitudinal ridges and about 2–4 short, thin elongate striae between each of the ridges; ventral annuli bear thin elongated microtubercles.

2. This structure can also be the last coxigenital annulus formed as a relatively smooth ridge and fused with anterior margin of genital shield (J. Amrine pers. comm. January 2014)

Setal lengths: c2 23, d 12, e 16, f 31, h1 4, h2 74; number of ventral annuli: 9 from rear; prodorsal shield margin to c2, 9 between c2 and d, 3 between c2 and 3a, 15 between d and e, 18 between e and f, and 4 between f and h1.

Male (n=3, Table 1). Males shorter than females and generally similar to them. The most contrasting differences are number of empodial rays (6–7 rays in males and 7–8 in females) and structure of external genitalia. External genitalia (Fig. 5). Genital area flat, subtriangular, 15 (15–16) wide, flanked laterally by 2–3 short longitudinal microtuberculate cuticular folds (Fig. 5 E g). The male external genitalia (= epiandrium) includes two plates anterior to setae 3a (Fig. 5 Ea, 5Eb) flanking the gonopore (Fig. 5 Ed), and a subtriangular postgenital region (Fig. 5 E e). The plate anterior to the gonopore, is a narrow, smooth, ribbon-like genital coverflap3 (Fig. 5 E a, coloured green). Posterior to the gonopore, is a thin plate (Fig. 5 E b, coloured in pink), notched anteriorly, bearing two distinct small rounded cuticle folds (Fig. 5 E c) latero-posterior to the notch at the place where eugenital setae are usually located. Eugenital setae seemingly absent. Postgenital region situated between tubercles of 3a, limited posteriorly by an arch-shaped semi-annulus (Fig. 5 E f) and sparsely covered by microtubercles. Setae 3a, 13 (13–14), 14 (14–15) apart.

3. We consider this plate to be homologous to the male genital coverflap described in Loboquintus subsquamatus Chetverikov et Petanovic 2013 (Fig.6 and text on p.5), but nonhomologous to the pregenital plate described in males and females of Pentasetacus araucariae (Schliesske, 1985) (Chetverikov et al. 2014a, figs. 7Ba, 7Da).

Nymph (n=5, Fig. 6) and larva (n=1). Measurements of immatures are given in Table 1. In comparison to adults, immatures lack the frontal lobe of the prodorsal shield and have subequal numbers of ventral and dorsal opisthosomal annuli (immature annuli not dorso-ventrally differentiated). Two longitudinal areas lateral to the tubercles of opisthosomal setae c2, d and e have thickened annuli (Fig. 6 A, blue arrows). In immatures, setae ve are situated on the anterior-lateral wall of prosoma between coxae I and the thick ridge-like anterior-lateral margin of the prodorsal shield4 (Fig. 6 B), which may be homologous to the submedian line II of adults. Microtubercles of opisthisomal annuli irregular, more numerous in nymphs than in larvae. Laterally, opisthosomal annuli without microtubercles.

4. We also observed setae ve in the same location (below antero-lateral margin of prodorsal shield) in SEM and CLSM images of adults of Sierraphytoptus ambulans Chetverikov and Sukhareva 2009 and Phytoptus alchemillae Jocić, Petanović and Vidović, 2011.

Host plant. Phoenix reclinata L. (Arecaceae). Mites were found inside folded young leaves. No apparent damage was observed.

Type material. Female holotype (slide #76-13, modified Berlese medium with iodine), about 25 female paratypes, 20 males, 15 nymphs and 2 larvae (on 8 slides) deposited in National Collection of Arachnida—Acari (NCA– Acari), Plant Protection Research Institute (ARC – PPRI, South Africa). Paratypes: about 20 females, 10 males and 10 immatures on 20 slides (12 in Hoyer medium and 8 in modified Berlese with iodine) deposited in the Acarological Collection of the Zoological Institute of Russian Academy of Sciences (ZIN RAS). All specimens from SOUTH AFRICA: Pretoria, National Botanical Garden, 25°44′18.92″S, 28°28′16.98″E, 13 March 2013, coll. S. Neser, P. E. Chetverikov and C. Craemer.

Designation of holotype female. A small circle was drawn on the lower surface of the type slide #76-13 using a black permanent marker. The holotype female is in the center of this circle accompanied by two other mites (paratype female and male), situated near the border of the black circle (Fig. 7).

Additional identified material. About 3 females from slide series #1351 deposited in ZIN RAS. All specimens from SOUTH AFRICA: Eastern Cape, Ntlakwe; 31°0′38″S, 30°2′17″E; 7 March 2013, coll. S. Neser, P. E. Chetverikov and C. Craemer.

Distribution. Specimens of M. reclinata n. sp. are at present known only from South Africa. The host plant, Phoenix reсlinata, is native to the African continent and the southern tip of the Arabian Peninsula. Currently, it is locally naturalized in many African and Mediterranean countries and can be found growing wild in nature (Barrow 1998). It is widely cultivated throughout the world including North and South America, and thus future surveys could reveal a wider distribution for M. reclinata n. sp.

Etymology. The specific epithet, reclinata, is a feminine noun in apposition, corresponding to the species name of the host plant.

Differential diagnosis. The new mite species is morphologically most similar to Mackiella phoenicis Keifer, 1939. These two species can be easily separated on the basis of the following characteristics: shape of the frontal lobe of prodorsal shield, microtubercle pattern of the dorsal opisthosomal annuli, ornamentation of coxae and measurements of selected characters (Table 3). In addition, the two species inhabit different host plants which significantly differ in geographical distribution.

CHARACTER M. reclinata n. sp. M. phoenicis Keifer, 1939 Shape of frontal lobe of Frontal lobe divided into two parts: subrectangular basal part and Frontal lobe entire, squarish prodorsal shield subcordial apical part (Figs 2 A; 3A,B; 4A,B)

Coxal ornamentation Distinct longitudinal lines and additional short striae (Figs 4 C, 5C) Coxae smooth Remarks. In his paragraph about type material, Keifer (1939, p.148) mentioned “ Type slide, …two paratype slides… and one jar bearing preserved mites”. Currently, the Keifer collection is kept at the USDA (USA, Maryland, Beltsville, curator R. Ochoa). Unfortunately, the first author did not find the type material during two visits to this collection (in August 2012 & March 2013). As type material was not available for study, the differential diagnosis is based on comparison with the original description only.

Structure Morphometrics Mean±SD Min–max CV (SD/Mean) * for abbreviations and measurements see Table 2 and Fig. 1.

Description of female internal genitalia (Figs. 1, 8, Tables 1, 4). A distinct longitudinal bridge (appearing as two brightly autofluorescing plates) is clearly seen under the genital coverflap in all studied females (Fig. 8 B b). The short posterior (postspermathecal) part of the bridge (Figs 8 B a, 8D a) is connected to a small cuticular triangular plate (Fig. 8 A c) extending anteriorly from the medio-posteror genital rim (Figs 8 A d, 8B d). Two subtriangular-suboval openings (leading to the spermathecal tubes) are situated in a small depression close to the medioposterior genital rim (not shown in the images). The proximal segment of the tube is short (about 0.5–1.0 µm), directed ventro-dorsally; the distal segment broad, sausage-like, directed anteriad (Figs 8 A e, 8C e, 8D e). Spermathecae (Fig. 8 D g) ovoid or teardrop-shaped (asymmetry index>1/2), directed laterad or posterolaterad, situated inside the space of the anterior angle of the anterior genital apodeme (Fig. 8 C h). Two zigzag-shaped coverflap hinges (Figs 8 C i, 8D i) attach laterally to the anterior genital apodeme connecting it to the lateral genital rim and the coverflap. The anterior genital apodeme consists of two parts (posterior and anterior) oriented in almost perpendicular planes. The posterior part (Fig. 8 B j) of the apodeme is subtrapezoidal-subtriangular, situated mainly in the horizontal-plane, extending anteriad and slightly inward; anterior part (Figs 8 B k, 8D k) of the apodeme is bent inward narrowing to a small apical plate bearing two terminal denticles (Figs 8 A l, 8D l), perpendicular to the longitudinal body axis. Anteriorly, the horizontal apodeme ends at the level between 1st and 2nd entire coxigenital annuli. The lateral and medial rami of coxal II apodeme are more or less discernible in all studied specimens; the lateral ramus is directed postero-laterad to the lateral arm of the anterior genital apodeme; the medial ramus is directed posterad or medio-posterad and ends at the level of the spermathecae. All measurements are given in Table 4.