Holostaspis flexuosa ( Michael, 1891 ) Babaeian & Mašán & Halliday, 2019

Babaeian, Esmaeil, Mašán, Peter & Halliday, Bruce, 2019, Review of the genus Holostaspis Kolenati, 1858 (Acari: Laelapidae), Zootaxa 4590 (3), pp. 301-341 : 312-316

Holostaspis flexuosa ( Michael, 1891) , comb. nov.

( Figs 19–32 )

Laelaps flexuosa Michael, 1891: 650 .

Loelaps (sic) flexuosus .— Wasmann, 1894: 198.

Myrmonyssus flexuosus .—Berlese, 1904b: 440; Freire, 2007: 218.

Myrmonyssus flexuosa .— Hunter & Hunter, 1963: 337.

Laelaspulus flexuosus .— Evans & Till, 1965: 284.

Myrmozercon flexuosa .— Shaw & Seeman, 2009: 54; Joharchi & Moradi, 2013: 253; Joharchi et al., 2015: 556.

Myrmozercon flexuosus .— Moreira, 2014: 325.

Specimens examined. Twenty females and four males—SW Slovakia, Little Carpathians Mountains, Horné Orešany Village, Majdan Settlement (48°28'10" N, 17°22'46" E), deciduous forest, under bark, in association with Camponotus sp. ( Hymenoptera , Formicidae ), altitude 260 m, June 13, 1994, coll. P. Mašán [some of these specimens have been misidentified and previously published under the name Hypoaspis (Holostaspis) isotricha by Mašán (2001)]; six females—SW Slovakia, Považský Inovec Mountains , Hrádok Village, Hrádocká Dolina Valley (48°41'26" N, 17°56'49" E), meadow, in wood, associated with Camponotus sp., altitude 290 m, May 28, 1993, coll. P. Mašán ; seven females and two males—SW Slovakia, Little Carpathians Mountains , Bratislava Capital, Železná Studienka Forest (48°11'36" N, 17°05'09" E), broadleaved deciduous forest, in wood, on ant bodies of Camponotus sp., altitude 255 m, April 22, 1991, coll. P. Mašán.

Diagnosis (female). Dorsal shield subpentagonal, abruptly tapering from level of S2, densely reticulate except smooth anteromedially, bearing 39 pairs of thickened setae and 4–5 unpaired accessory setae between J1–J4; dorsal setae increasing in length from anterior to posterior, with tips reaching bases of following posterior setae of opisthonotal region; vertical setae (j1) thickened, 25–30 µm long and shorter than other dorsal setae except z1 (12–15 µm). Sternal shield wider than long, mostly smooth except weakly reticulate anteriorly and laterally between st2–st3. Parapodal-exopodal platelets behind coxa IV expanded posteriorly. Epigynal shield relatively short, well distant from anal shield. Anal shield subtriangular, wider than long (L/W=0.7), with anteromedial margin convex, anterolateral angles slightly projecting, blunt; postanal seta thickened and approximately twice as long as adanals. Peritremes anteriorly reaching level of s1. Epistome with pointed apex. Fixed digit of chelicera with one tooth, movable digit edentate; Femur I with 14, genu III and IV each with ten and tibia III with nine setae.

Description. FEMALE (N=5) ( Figs 19–29 )

Dorsal idiosoma ( Fig. 19 ). Idiosoma 530–600 µm long and 375–410 µm wide; dorsal shield 440–480 µm long and 295–325 µm wide, widest at level of S2, densely reticulate throughout except smooth anteromedially, not completely covering dorsal surface, exposing a broad strip of soft integument laterally and posteriorly; bearing 39 pairs of setae: 22 pairs (j1–j6, z1–z6, s1–s6, r2–r5) in podonotal area and 17 pairs (J1–J5, Z1–Z5, Px2–Px3, S1–S5) in opisthonotal area and 4–5 unpaired accessory setae between J1–J5; with 21 pairs of discernible pore-like structures (five pairs of gland pores and 16 pairs of lyrifissures). Dorsal shield setae relatively long and thick (except z1), all with smooth margin ( Fig. 20 ), except seta Z5 with distal pilosity, setae progressively longer from anterior to posterior region of shield; lengths of some setae: j 1 25–30 µm, j5 39–43 µm, J4 48–54 µm, J5 39–44 µm, z 1 13–17 µm, Z5 64–70 µm, S4 52–58 µm, S5 53–58 µm.

Ventral idiosoma ( Fig. 21 ). Tritosternum with short columnar base (17–25 µm) and pilose laciniae (62–70 µm). Sternal shield subrectangular, 95–112 µm long and 129–138 µm wide, widest at level of coxae II–III (198–207 µm), bilobed anteriorly and concave posteriorly, smooth medially and with few, irregular lineation-reticulation in anterior and lateral areas; setae with tips not reaching bases of following ones (st1 35–40 µm, st2 and st3 35–37 µm); lyrifissures iv1 and iv2 slit-like. Metasternal setae (st 4 26–30 µm) and associated lyrifissures iv3 placed on soft integument; endopodal platelets III–IV subtriangular, narrow and usually with anterior part fused to posterolateral margins of sternal shield (rarely free). Epigynal shield tongue-shaped, relatively short and wide, moderately expanded behind coxa IV and bulging laterally at level posterior to st 5, 243–250 µm in length and 161–174 µm in width, 136–141 µm at level of st5; anterior hyaline margin curved, reaching level of st1; posterior portion with small incision on each lateral margin and lineate ornamentation pattern forming usually eight elongate cells; genital setae (st5 35–37 µm) placed close to mediolateral margins of the shield and associated lyrifissures iv5 on soft integument; soft integument between iv5 and Zv1 each with 1–2 minute adgenital sclerites, right one partially fused to genital shield. Parapodal platelets surrounding coxa IV well expanded posteriorly. Metapodal platelets suboval, rather small, 25–27 µm long. Anal shield triangle-shaped, 64–68 µm long and 87–95 µm wide, with short anterolateral angles obtusely pointed, anterior margin moderately convex, with weak semicircular sculptural lines on anterior portion; postanal seta 45–51 µm long, thickened and longer than adanal setae (26–33 µm); cribrum with wide band of spicules, reaching level slightly anterior to postanal seta. Lateral and opisthogastric soft integument with 18 pairs of thick setae, each with base inserted on small and rounded sclerite; setae Jv1 –Jv3, Zv1 and Zv2 shorter and smooth, remaining setae long and sparsely pilose distally. Poststigmatic section of peritrematal shield narrow, relatively long, reaching posterior margin of coxa IV, and tapered posteriorly.

Gnathosoma ( Figs 22–25 ). Epistome subtriangular, pointed apically, often with some irregularities as in Fig. 22 . Corniculi weakly sclerotised, relatively stout, bluntly pointed; internal malae short, with tips reaching slightly beyond corniculi, and finely serrate laterobasally; labrum long, blade-like and with pilose surface ( Fig. 23 ). Deutosternal furrow with almost parallel lateral margins, with six transverse rows of denticles (each with 8–12 denticles). Lengths of hypostomal and palpcoxal setae: h 1 25–27 µm, h 2 15–20 µm, h3 37–42 µm, pc 22–27 µm. Palp setation 2-5-6-14 -15, as in Fig. 24 . Shape and dentition of chelicera as in Fig. 25 ; lengths of cheliceral articles: the second segment 87–92 µm, fixed digit 27–30 µm and movable digit 25–27 µm.

Legs ( Figs 26–29 ). Legs setation as in other species in the genus, except for the following four segments, each with one additional seta: femur I with 14 setae (2 3/ 2, 2/3 2; one additional av), genu III with ten setae (2 2/1, 2/1 2; one additional pl), genu IV with ten setae (2 2/1, 3/0 2; one additional pl), and tibia III with nine setae (2 1/1, 2/1 2; one additional pl). Tarsi I–IV each with a pair of claws and pulvillus. Lengths of legs: leg I 426–446 µm, leg II 297–309 µm, leg III 322–347 µm, leg IV 483–497 µm.

Setae ad1 on femur II, al on trochanter III, ad1 on femur III, ad on trochanter IV and ad1, ad2 on femur IV thickened.

MALE (N=3) ( Figs 30–32 )

Idiosoma. Dorsal shield 377–400 µm long and 240–260 µm wide ( Fig. 30 ). Separate presternal shield absent. Sternitogenitoventral shield 280–288 µm long, with irregular posterolateral margin, bearing 8–9 pairs of setae (st1–st5, Jv1, Jv2, Zv1 and Zv2; sometimes Zv2 asymmetrically off the shield) and four pairs of lyrifissures; anteromedial area smooth and without sculpture, anterolateral areas with weak, short and sparse lines, posterior area distinctly reticulate ( Fig. 31 ). Anal shield free, relatively distant from sternitogenitoventral shield. Other idiosomal characters similar to those in female.

Gnathosoma . Fixed digit of chelicera with one small tooth close to terminal hook, pilus dentilis not discernible; movable digit not distinct, fully transformed into long, curved spermatodactyl (78–82 µm), progressively tapering into a blunt apex; dorsal seta conspicuous, markedly enlarged ( Fig. 32 ). Other gnathosomal structures similar to those in female.

Remarks. The following ecological, geographic and morphological features suggests that the specimens that we examined are conspecific with those described by Michael (1891) as Laelaps flexuosa : (1) host-specific association with ants of the genus Camponotus ; (2) distributed in Central Europe; (3) dorsal shield not completely covering dorsal idiosoma (original illustration does not show lateral strips of uncovered soft integument, but old illustrations are usually not accurate in all details); (4) form (subpentagonal) and size of idiosoma; (5) proportion between idiosoma and legs, and between the legs I–IV; (6) position and number of dorsal setae are relatively similar (if dorsal shield setae and those placed dorsally on marginal soft integument are counted together); (7) setae progressively longer from anterior to posterior region of shield; (8) clunal setae (Z5) apparently longest; (9) setae J5 reaching well beyond the posterior margin of the shield; (10) number and position of unpaired setae; (11) movable digit of male chelicera fully transformed into long and curved spermatodactyl; (12) dorsal seta on male chelicera conspicuously enlarged; (13) femur I with five ventral setae (2 3/2, 2/3 2), tibia III and genu IV with two posterolateral setae (2 1/1, 2/1 2 and 2 2/1, 3/0 2, respectively), as additionally described by Evans & Till (1965) (as Laelaspulus flexuosus , pp. 284–286), probably based on original specimens of Michael’s mite collection in London.

The species was described by Michael (1891) in Laelaps Koch, 1836 . It has sometimes been tentatively considered as a member of Myrmonyssus Berlese, 1903 by Berlese (1904b), Hunter & Hunter (1963), and Freire (2007), or Myrmozercon Berlese, 1902 by Shaw & Seeman (2009), Joharchi & Moradi (2013), Moreira (2014), and Joharchi et al. (2015). Evans & Till (1965) treated Laelaps flexuosa in the genus Laelaspulus , a taxon originally established as a subgenus of Myrmonyssus by Berlese (1904b). At present, both Myrmonyssus and Laelaspulus are considered to be synonymous with the older name Myrmozercon ( Rosario & Hunter, 1988; Shaw & Seeman, 2009). Recently, Shaw & Seeman (2009) placed L. flexuosa in Myrmozercon , based only on the brief initial description of Michael (1891), with several illustrations of the female dorsal idiosoma with legs, gnathosoma and male chelicera, and also on the leg chaetotaxy subsequently given by Evans & Till (1965). We have placed L. flexuosa in Holostaspis , primarily because of the following combination of features: (1) claws on legs I–IV well developed, large; (2) dorsal shield setation holotrichous, with 39 pairs of setae, including two pairs of Px setae; (3) peritremes longer, anteriorly reaching beyond middle of coxa II; (4) deutosternal grove with six transverse rows of denticles; (5) palp trochanter with two ventral setae, including v2; (6) female cheliceral digits similar in size, with fixed digit only slightly shorter than movable digit.

The systematic position of this species in Holostaspis makes the definition of the genus more difficult in some respects, and is probably is only provisional until related genera are more fully revised. Holostaspis flexuosa could be excluded from Holostaspis because some of its character states differ from those of other Holostaspis species: (1) five ventral setae on femur I (only four setae in congeners); (2) two posterolateral setae on genua III–IV and tibia III (only one posterolateral seta in congeners, except H. michaeli ); (3) dorsal shield relatively smaller, not completely covering dorsal idiosoma (this is also the case of H. iranica ); (4) epigynal shield a bit wider and shorter than usual, distant from anal shield (longitudinally elongate and reaching near the anal shield in congeners); (5) genital setae st5 inserted farther medially on the the epigynal shield (st5 inserted on or close to lateral margin of epigynal shield in congeners); (6) in male with a free anal shield (anal plate fused with anterior elements into a holoventral shield in other species with known males, namely H. montana and H. oophila ); (7) parapodal platelets moderately expanded behind coxa IV (narrow and crescent-shaped in congeners); (8) poststigmatic sections of peritrematal shields moderately elongate, with their ends reaching slightly beyond posterior margins of coxa IV (short and not reaching the posterior margin of coxa IV in most congeners, but more notably extended and expressed in H. iranica ); (9) movable digit of male chelicera fully transformed into spermatodactyl (movable digit well developed, including a terminal hook, masticatory surface with teeth and long spermatodactyl in H. montana ); (10) dorsal seta of fixed digit of male chelicera conspicuous (not seen in H. montana ). Note that the male of two species have been described, and the chelicera only for two species, therefore differences 6, 9–10 have limited significance.

Figures

FIGURES 19–25. Holostaspis flexuosa, female. 19. Dorsal idiosoma; 20. Enlarged view of a dorsal seta; 21. Ventral idiosoma; 22. Epistome; 23. Ventral gnathosoma; 24. Palp, right side, ventral view; 25. Chelicera.

FIGURES 26–29. Holostaspis flexuosa, female. 26. Leg I; 27. Leg II; 28. Leg III; 29. Leg IV.

FIGURES 30–32. Holostaspis flexuosa, male. 30. Dorsal idiosoma, left portion; 31. Ventral idiosoma; 32. Chelicera.