Lasioseius cheiroseioides, Mašán, 2023

Mašán, Peter, 2023, On some blattisociid mites (Acari: Mesostigmata: Lasioseius, Cheiroseius) from Slovakia, with notes on the genus Hyattella sensu Krantz, 1962, Zootaxa 5361 (2), pp. 159-180 : 160-168

Lasioseius cheiroseioides sp. nov.

( Figs 1–15 , 24 , 27 )

Material examined

Holotype female: SW Slovakia, Podunajská Rovina Flatland, Svätý Jur Town, Panónsky Háj Forest, oak forest ( Quercus spp. ), under the bark of an old oak, in galleries with larvae of Cerambyx cerdo Linnaeus ( Coleoptera : Cerambycidae ) , elevation 130 m, 21 March 2023 . Paratypes: one female, with the same data as the holotype; one female, SW Slovakia, Borská Nížina Lowland, Šaštín-Stráže Town, oak forest with admixed pines ( Pinus sylvestris ), in dying oak and galleries with larvae of C. cerdo , elevation 170 m, 5 June 2021 ; 25 females, SW Slovakia, Podunajská Rovina Flatland, Bratislava Capital, Rusovce Settlement, park, under the bark of an old oak, in galleries with larvae of C. cerdo , elevation 130 m, 26 June 2023. All type specimens were collected by the author, and deposited in the Institute of Zoology of the Slovak Academy of Sciences, Bratislava , Slovakia.

Description (Female)

Diagnosis. Podonotal and opisthonotal regions of dorsal shield with 21 and 15 pairs of setae, respectively. Dorsolateral soft cuticle with eight pairs of marginal setae and four pairs of submarginal setae. Setae z1, s2, and J5 shortest and needle-like, other setae of dorsal shield slightly thickened, finely tricarinate, and about as long as distance to each succeeding seta. Presternal area with a pair of platelets widely connected to anterior margin of sternal shield. Epigynal shield relatively large, longer than sternal or ventrianal shield. Ventrianal shield with four pairs of pre-anal setae (JV1–JV3 and ZV2). Opisthogaster with complete series of pre-anal setae (JV1–JV5 and ZV1–ZV5); JV5, ZV4, and ZV5 slightly thickened and tricarinate, other ventral setae short and needle-like. One pair of metasternal platelets and two pairs of metapodal platelets present. Spermathecal apparatus formed as pear-shaped structure. Epistome triramous. Fixed and movable digits of chelicerae with 8–9 and three teeth, respectively. Legs I and IV longer than dorsal shield; tarsi II and III with two flattened and curved macrosetae (ad2 and pl2 on tarsus II, ad2 and pd2 on tarsus III), tarsus IV with one such macroseta (ad2).

Dorsal idiosoma ( Figs 1 , 7 ). Idiosoma 670‒695 long and 410‒455 wide at level of r5 (three specimens measured), almost regularly oval, not completely covered by shield at lateral margins. Dorsal shield elongate and gradually narrowing behind humeral setae (r3), 665‒690 long and 390‒405 wide at widest point at level of r3, with 36 pairs of setae and conspicuous reticulate pattern on entire surface. Dorsal shield setae ( Fig. 14 ) relatively well developed and thick, almost spine-like, usually slightly inflated basally, and tricarinate (setal carinae smooth, without serration or denticulation); most dorsal setae similarly long, reaching base of following setae in longitudinal row or slightly beyond; only z1, s2, and J5 thin and distinctly shorter, z1 and s2 smooth or only imperceptibly tricarinate, J5 finely serrate; r3 longest. Podonotum of dorsal shield with 21 pairs of setae (j1–j6, z1–z6, s1–s6, and r2–r4), opisthonotum with 15 pairs of setae (J1–J5, Z1–Z5, and S1–S5); marginal setae r5, r6, R1 – R6 and four (often asymmetrically three) pairs of submarginal setae (UR) placed on soft cuticle adjacent to shield margin, each with base on small suboval and well-sclerotised platelet. The lengths of some selected dorsal setae are as follows: j1 54–59, j2 59–65, j3 66–72, j4 63–71, j5 64–68, j6 66–73, z1 30–37, s2 30–33, r2 51–55, r3 80–87, r4 63–67, r5 58–65, r6 49–57, other podonotal setae 64–72, J1 65–72, J2 61–68, J3 59–64, J4 57–62, J5 18–21, Z1 65–74, Z2 60–66, Z3 58–67, Z4 59–66, Z5 70–80, S1 61–66, S2 60–66, S3 61–69, S4 61–65, S5 53–59, R1 ‒ R6 40–50, and UR -setae 30–36.

Ventral idiosoma ( Figs 2 , 12, 13 ). Tritosternum with short columnar base and two laciniae; laciniae separated along their entire length, each with sparse, fine and short pilosity. Presternal area with a pair of relatively small and partially to completely fused platelets widely connected to anterior margin of sternal shield; each platelet with usually three fine transverse lines; area of fusion of the two platelets weakly sclerotised. Sternal shield subquadrate, 160‒180 long and 130‒145 wide at narrowest point between coxae II, with smooth surface, antrolateral angles well developed and laterally directed, posterior margin almost straight, three pairs of subequal and apically attenuated setae (st1‒st3), and two pairs of poroids (iv1 and iv2). Each metasternal seta (st4) and associated poroid (iv3) on a small and suboval or drop-like metasternal platelet posterior to posterolateral margins of sternal shield. Endopodal platelets reduced and not well-sclerotised, indistinct. Epigynal shield relatively large, elongate, 255‒275 long, 108‒ 115 wide at widest point posterior to setae st5, 92‒97 wide at level of st5, and 126‒138 wide at widest anterior part, with narrowly convex anterior margin reaching level between setae st2 and poroids iv2, moderate medial constriction, and nearly straight posterior margin; surface largely smooth, except for a pattern of fine lines in anterior part and two diagonal lines converging anteriorly in posterior part; setae st5 on shield surface near posterolateral margins; genital poroids (iv5) on soft cuticle posterior to st5. Four postgenital sclerites present, weakly sclerotised. Exopodal platelets fused into long and narrow plates, each parallel to peritrematal shield; parapodal part of exopodal platelets IV narrowly connected to short poststigmatic part of peritrematal shields. Peritremes relatively broad, with anterior ends reaching about level of paravertical setae (z1); peritrematal shields narrow, developed along outer side of peritremes, and fused with podonotal part of dorsal shield at level of setae s1. Two pairs of suboval metapodal platelets posterior to coxae IV, anteromedial pair conspicuously smaller than posterolateral pair (23–28 long). Ventrianal shield relatively small, inversely pear-shaped, slightly wider than long (192‒212 long and 209‒222 wide at widest anterior part), abruptly narrowed behind setae JV3, almost straight anteriorly and convex anterolaterally and posteriorly; with four pairs of pre-anal setae (JV1‒JV3 and ZV2) in addition to three circum-anal setae and gland pores gv3 near posterolateral margins at level between setae ad and pa; postanal seta longer than adanal setae (pa 44‒47, ad 25–31), JV2 distinctly longer than other pre-anal setae; anus small (25‒30 x 21‒24 in size), placed in posterior part of shield; pre-anal surface with reticulate pattern dominated by transverse lines, remaining surface without conspicuous ornamentation and smooth, except for narrow cribrum along posterior margin. Soft opisthogastric cuticle with six pairs of pre-anal setae (JV4, JV5, ZV1, and ZV3‒ZV5). All ventral setae smooth and needle-like, except for the more robust tricarinate setae JV5, ZV4, and ZV5, with the following lengths: st1 and st2 45–50, st3 46–54, st4 44–52, st5 38–44, JV1 40–45, JV2 46–58, JV3 34–39, JV4 24–28, JV5 50–57, ZV1 25–30, ZV2 36–39, ZV3 29–37, ZV4 33–37, and ZV5 41–45.

Sperm induction structures. Spermathecal apparatus ( Fig. 15 ) well developed, unusually large (total length 75‒80), and pear-shaped, with a well-sclerotised neck, an almost regularly spherical vesicle or saccule (33‒36 in diameter), and with a long, thin, and convoluted duct leading from an indistinct atrium to a slightly thickened terminus.

Gnathosomal structures ( Figs 6 , 8‒11 ). Corniculi horn-like, normal in size and spacing; internal malae each formed as a pointed projection with imperceptibly serrated lateral margins, projecting far beyond corniculi; hypognathal groove with seven rows of denticles, rows similar in width, with many denticles and connected laterally by longitudinal lines; subcapitular setae ( Fig. 8 ) smooth and needle-like, h2 shortest, the others similar in length, but pc slightly longer than h1 and h3 (h1 56–59, h2 21–23, h3 55–58, pc 58–62). Anterior margin of epistome triramous, rami with denticulate distal or apical margins; lateral rami about half as long as median ramus but much wider than median ramus ( Fig. 9 ). Middle article of chelicerae unusually long (240‒250; cheliceral digits only about 1/4 length of middle article); cheliceral digits similar in length and size, dentate; movable digit 63‒68 long, tridentate (all teeth in distal part of digit); fixed digit with eight or nine teeth, including two small subterminal teeth near terminal hook, 4‒5 medial teeth slightly larger than a pair of most proximal teeth; pilus dentilis short and small, spine-like; dorsal seta relatively long and thin ( Fig. 6 ). Palp trochanter with two long setae, both with thickened base and attenuated distal part; palptarsal claw two-tined.

Legs. Each with well-developed pretarsus and ambulacral apparatus, including pulvillus with three rounded lobules and two claws (claws of tarsi I distinctly smaller than those of tarsi II‒IV); legs I and IV longer and legs II and III shorter than idiosoma: legs I 690–710, legs II and III 575–590, and legs IV 740–815 long. Leg setae smooth and acicular, mostly similar in shape and length, except modified setae formed as elongate, flattened, and distally curved macrosetae (ad2 on tarsi II‒IV, pl2 on tarsi II, and pd2 on tarsi III). Chaetotactic formulae for each leg segment as follows: leg I – coxa (2), trochanter (6), femur 2-3/1, 2/2-2 (12), genu 2-3/2, 3/1-2 (13), tibia 2-3/2, 3/1-2 (13); leg II – coxa (2), trochanter (5), femur 2-3/1, 2/2-1 (11), genu 2-3/1, 2/1-2 (11), tibia 2-2/1, 2/1-2 (10); leg III – coxa (2), trochanter (5), femur 1-2/1, 1/0-1 (6), genu 2-2/1, 2/1-1 (9), tibia 2-1/1, 2/1-1 (8); leg IV – coxa (1), trochanter (5), femur 1-2/1, 1/0-1 (6), genu 2-2/1, 3/0-1 (9), tibia 2-1/1, 3/1-2 (10).

Etymology

The specific name is derived from the generic name “ Cheiroseius ” and the Greek suffix “- oides ” (resembling), referring to the fact that this new species resembles some species of the genus Cheiroseius in general appearance (well-sculptured dorsal shield, elongated legs) and in some specific characters (e.g., presence of specialised macrosetae on the tarsi II‒IV, shape of the epistome).

Taxonomic notes

Lasioseius cheiroseioides is easily recognised, especially by the presence of specifically formed macrosetae (ad2 on tarsi II‒IV, pl2 on tarsi II, and pd2 on tarsi III), the conspicuously elongate middle article of the chelicerae (the cheliceral digits are about 1/4 as long as the middle article), the elongate legs (of which the first and fourth pairs are longer than the idiosoma), and the three pairs of marginal setae on the dorsal shield (r2‒r4).

Of the more than 200 valid species of the genus Lasioseius , only a few species have been described that have developed modified macrosetae on the tarsi II‒IV, but most often it is only an unpaired macroseta on tarsus IV. The homology of the specialised macrosetae in individual species of Lasioseius was studied and reviewed by Lindquist & Moraza (2016). These authors pointed out a certain general pattern in the chaetotaxy of the elongate and usually more or less strap-like tarsal macrosetae: tarsus II with two modified macrosetae (ad2 and pl2), tarsus III with one macroseta (ad2), tarsus IV with 0‒1 macroseta (either al2 or pl2, rarely pd2). However, the pattern described above varies in several respects, and only some of the macrosetae listed may be present. Lasioseius cheiroseioides is unusual in the presence of two macrosetae, namely pd2 on the tarsus III and ad2 on the tarsus IV. Also, the flattened (strap-like) and distally whip-like form of the macrosetae in the new species is rarely expressed in members of the genus [ L. epicrioides ( Krantz, 1962) , L. americanellus ( De Leon, 1964) , L. elegans Fain, Hyland & Aitken, 1977 , and L. chelaserratus Naeem, Dobkin & OConnor, 1985].

Lasioseius cheiroseioides is most similar to L. ningxiaensis Bai, Ma & Yan, 2014 [in Bai et al. (2014); = L. multisetus Ma & Bai, 2006 ], a species found in China in the same habitat as the new species (galleries of cerambycid larvae). Both species can be easily distinguished from each other, especially by the placement of the anteromarginal setae r5 and r6, which may be located on the dorsal shield in L. ningxiaensis or on the soft cuticle in L. cheiroseioides .

Some important morphological structures of L. ningxiaensis are not described in sufficient detail, but undoubtedly it can be considered as the closest relative of L. cheiroseioides and together with L. lacunosus Westerboer, 1963 , it could be placed in a complex of related species that share atypical or little specific characters for the genus, at least like the chaetotaxy of the tarsi II‒IV and the form and dentition of the chelicerae.

Using my own available specimens of L. lacunosus from Slovakia, it is possible to shed more light on the individual similarities between members of this species complex. Lasioseius lacunosus has homologous macrosetae on the tarsi II‒IV like the new species, but they are relatively shorter, which might be related to the relatively shorter legs compared to the body. The middle article of the chelicerae is analogous in the conspicuously elongated form, the dentition of both digits, and some other structures: the movable digit is tridentate, with teeth on the distal part of the masticatory surface, and the fixed digit is oligodentate, with a group of 4‒5 small teeth on the medial masticatory surface; the pilus dentilis is short and stout, but the dorsal seta is long and thin. In addition, the distal part of the middle article of the chelicerae has a conspicuous, peculiar, and longitudinally oriented slit-like furrow found in both species ( Fig. 20 ). The epistome is very similar in both species, triramous, with apical denticulation or strong serration, and the medial ramus is widened apically and narrower than the lateral ones. The species have the full number of j / J, z / Z, s / S, and r / R rows of setae, with different arrangement of anteromarginal setae on/off the dorsal shield: the shield with r2‒r 4 in L. cheiroseioides and r2‒r 5 in L. lacunosus (r2‒r 6 in L. ningxiaensis ). The same number of four pairs of submarginal setae (UR) are located on the soft cuticle adjacent to the shield margin (UR setae are not shown or annotated in L. ningxiaensis ). The most important difference between L. cheiroseioides and L. lacunosus is the number of pre-anal setae on the ventrianal shield in addition to the three circum-anal setae, four pairs in L. cheiroseioides (JV1‒JV3 and ZV2) and six pairs in L. lacunosus (JV1‒JV4, ZV2, and ZV3).

Another feature of significant differential value that would also support the validity of this group as a separate taxon within the genus (in a new or revised taxonomic concept of the genus) is the unusual presence of slightly enlarged and spurred legs II in males ( Figs 21, 22 , 30 ). In males, the anteroventral seta (av) on the femur II is modified into a relatively conspicuous and well-sclerotised spur ( Fig. 21 ), as is av2 on the tarsus II ( Fig. 22 ). A similar spur-like av2 is described only in males of the two unrelated species L. furcisetus Athias-Henriot, 1959 and L. corticeus Lindquist, 1971 . Male legs II are well spurred only in L. kshamae Bhattacharyya, 2003 , but without modified seta av2 on the tarsus.

Figures

FIGURE 7. Lasioseius cheiroseioides sp. nov., dorsal idiosoma of female. Scale bar: 100 µm.

FIGURES 1–6. Lasioseius cheiroseioides sp. nov., female. 1. Dorsal idiosoma; 2. Ventral idiosoma; 3. Tarsus II, dorsal view; 4. Tarsus III, dorsal view; 5. Tarsus IV, dorsal view; 6. Cheliceral digits, lateral view. Scale bars: 100 µm (Figs 1‒5), 25 µm (Fig. 6).

FIGURES 8‒11. Lasioseius cheiroseioides sp. nov., female. 8. Ventral gnathosoma; 9. Epistome; 10. Chelicera, dorsal view, with chelicera of Lasioseius epicrioides for comparison (on the left); 11. fixed digit of chelicera, dorsal view. Scale bars: 25 µm.

FIGURES 12‒14. Lasioseius cheiroseioides sp. nov., female. 12. Ventral shields; 13. Sternal and metasternal shields, with anterior part of epigynal shield; 14. Detail of posterolateral dorsal setae. Scale bars: 50 µm (Figs 12, 13), 25 µm (Fig. 14).

FIGURES 15–17. Lasioseius spp., females. 15. L. cheiroseioides sp. nov., sperm-reception structures, lateral view; 16. L. lacunosus, dorsal idiosoma; 17. L. lacunosus, ventral gnathosoma. Scale bars: 25 µm (Fig. 17), 50 µm (Fig. 15), 100 µm (Fig. 16).

FIGURES 23–26. Lasioseius spp., females. 23. L. lacunosus, ventral shields; 24. L. cheiroseioides sp. nov., dorsal shield sculpture of hexagonal area; 25. L. lacunosus, dorsal shield sculpture of hexagonal area; 26. L. epicrioides, dorsal shield sculpture of posteromedial area. Scale bars: 50 µm (Fig. 23), 25 µm (Figs 24‒26).

FIGURES 27–31. Lasioseius spp., dorsoventral habitus. 27. L. cheiroseioides sp. nov. (female); 28. L. epicrioides (female); 29. L. diffindatus (female); 30. L. lacunosus (male); 31. L. lacunosus (female). Scale bar: 300 µm.

FIGURE 18–22. Lasioseius lacunosus. 18. Chelicera (male), lateral view; 19. Epistome (male); 20. Chelicera (female), lateral view; 21. Femur II (male), ventral view; 22. Tarsus II (male), ventral view. Scale bars: 25 µm (Figs 18‒20), 50 µm (Figs 21, 22).