Zygoseius lindquisti, Ahadiyat, Ali & Beaulieu, Frederic, 2016

Ahadiyat, Ali & Beaulieu, Frederic, 2016, Two new mite species of the genus Zygoseius Berlese from Mexico (Acari, Mesostigmata), ZooKeys 629, pp. 11-49 : 26-44

Taxon classification Animalia Mesostigmata Pachylaelapidae

Zygoseius lindquisti sp. n. Figures 15, 16, 17, 18, 19, 20, 21, 22, 23-26, 27, 32, 33, Plate 2

Diagnosis.

Dorsal shield oval, densely micropunctate, with relatively distinct reticulation and lineation, except more weakly reticulated medially between setae j4-6. Edges of lateral parts of dorsum smooth. Dorsal setae smooth, except J4 and J5 with a few barbs basally; all setae less than 35 long; setae z6, s6, and all opisthonotal setae (except J5 and Z5) 1.5 –2× as long as other setae. Sternal shield densely micropunctate, except in the regions of setal insertions. Epigynal shield conspicuously punctate in anterior 2/3, punctae lighter posteriorly. Ventrianal shield distinctly lineate in anterior half, reticulate laterally and posteriorly; setae JV2 slightly longer than other setae on shield. Peritrematal shield micropunctate throughout, punctae larger in poststigmatic region. Soft lateral and opisthogastric cuticle with nine pairs of setae. Epistome bifurcate, thin projections slightly converging, about twice as long as distance between their bases, sparsely serrated in apical half. Hypostomal setae h1 about twice as long as h2, and subequal to h3. Femur I with seta pd2 thickened. Spermathecal apparatus with a small, kidney-shaped spermatheca directly connected to a globular, large sperm reservoir, followed by a long spermatic canal with diverging walls.

Description

Female (n = 2). Dorsal idiosoma (Figs 15, 32). Dorsal shield oval, 396-413 long, 278-283 wide (length/width ratio: 1.40-1.48), completely covering idiosoma; edges of lateral parts of dorsum smooth, with no marginal serration; shield densely micropunctate throughout, distinctly reticulate-lineate, more weakly reticulate medially, especially between setae j4-j6 and posterad setae Z3-4 and around and posterad J5. Dorsal shield with 37 pairs of setae, 23 and 14 pairs on podonotal and opisthonotal regions, respectively; lacking setae J3. Dorsal setae less than 35 long, all smooth, acuminate, slightly swollen basally, except J4-5 finely pilose basally (Fig. 17A, B). Opisthonotal setae about twice as long as podonotal setae (Table 1). Dorsal idiosoma with 23 pairs of pore-like structures, including seven gland openings and 16 poroids.

Ventral idiosoma (Figs 16, 33). Tritosternum with a trapezoidal base, 23-28 long, 12-14 wide proximally, 4-6 wide apically, and a pair of laciniae (61-64 long). Laciniae with barbs relatively short and blunt (Fig. 18). Sternal shield 98-102 long, 66-71 wide (length/width ratio: 1.44-1.48), bearing two pairs of poroids and three pairs of smooth, subequal setae st1-3 (Table 1); shield anterolateral arms long, contiguous to subtriangular exopodal plate between coxae I and II; anterior margin with distinct median notch and two subtriangular projections; posterior margin truncate; shield densely micropunctate throughout, except smooth around sternal setae. Complex of metasternal and endopodal elements arc-shaped, mostly smooth, punctate in restricted areas, bearing simple setae st4 and poroids iv3. Epigynal shield trapezoidal, 85-87 long, 22-24 long from st5 to posterior margin, 81-84 wide (length/width ratio: 1.03-1.07), conspicuously punctate in anterior 2/3, punctae lighter posteriorly; shield with transverse convex line passing behind setae st5; anterior hyaline portion rounded, indistinct; shield closely abutting ventrianal shield; three pairs of suboval to subcircular sigillae medially, posterior ones larger, oval. Setae st5 smooth, inserted near shield lateral margins. Poroids iv5 near posterolateral margins of epigynal shield. Ventrianal shield subpentagonal, broad, 153-154 long, 189-196 wide (length/width ratio: 0.79-0.81), with straight anterior margin; distinctly lineate in anterior half, reticulate laterally and posteriorly; cells micropunctate inside and along cell margins; shield bearing five pairs of pre-anal and three circum-anal setae, all smooth; setae JV2 slightly longer than other setae; other setae subequal, except ZV1 shorter (Table 1); para-anal setae inserted at level of anterior margin of anal opening; gland openings gv3 on posterolateral margins of shield at level of posterior margin of anus; cribrum well-developed, 2-3 rows of spicules, extending along posterior shield margin between gv3 openings; anal opening 25-26 long, 21-22 wide, subtriangular to subcircular, located in posterior fifth or fourth of shield. Peritreme 191-198 long, densely covered with aciculae, extending anteriorly near seta z1, with one gland pore (gp) at mid-level of coxa II. Peritrematal shield wide, fused to exopodal, parapodal and metapodal elements, extending well behind posterior level of coxae IV; shield micropunctate, with larger punctae in poststigmatic region, with four pore-like structures (id3, gd3, id7, gv2). Exopodal element between coxae II–III fused with other exopodal-peritrematal elements (Fig. 19). Soft lateral and opisthogastric integument plicate, bearing nine pairs of setae, 15-30 long, slightly thickened basally, marginal setae as the longest. Soft cuticle with five pairs of poroids, including four ivo, idR3, and an oval platelet bearing two pore-like structures, at level of posterior margin of peritrematal shield.

Gnathosoma. Epistome (Fig. 20) bifurcate, with two slender projections (16-20 long), forming a U shape at their bases (separated by 8-10), slightly converging; distal halves of projections sparsely serrated on inner margin (in one specimen) or both inner and outer margins (in other specimen), margins proximally smooth; basal margin finely serrated laterally; a transverse series of blunt to sharp tubercles posteromedially, and fewer series laterally. Corniculi (Fig. 21) short, 24-26, horn-like. Internal malae (Fig. 21) finely developed, reaching slightly beyond corniculi; anterolateral margins fimbriate, inner margins smooth; labrum fine, shorter than internal malae, finely fimbriate distally. Hypostomal and capitular setae (Fig. 21) smooth, needle-like, h3 (21-about 28) and h1 (21-25)>pc (about 13-17)>h2 (8-9). Deutosternum (Fig. 21) with 6-7 transverse rows of denticles, followed posteriorly by a smooth ridge; posteriormost row of denticles widest; two anteriormost (1st and 2nd) and posterior-most (5th and/or 6th) rows with larger denticles; numbers of denticles from anterior to posterior rows: 8-10, ~ 9, 10-11, ~ 10-11, 12-14, 15-18. Cheliceral teeth not clearly discernable (digits oriented dorsoventrally); first cheliceral segment 35-44 long, second segment and fixed digit unclear; movable digit 27-29; width of second segment 17-21. Palp (Fig. 22) 105-113 long, dorsal surfaces of femur and genu with some sigillae; trochanter 13-18 long, femur 34-36, genu 27-29, tibia 23-26; apotele 3-tined. Palp chaetotaxy: from trochanter–tibia 2-5-6-14 setae; trochanter 0 0/1 0/1 0, femur 1 2/0 1/0 1, genu 2 2/0 1/0 1; tibia as in Fig. 22. All palpal setae smooth, tapered; av (v2, sensu Evans 1963b) on trochanter strongly bent inwards (Fig. 27); al on femur, al1-2 on genu and one of al setae on tibia short and spatulate; genu with stout spur dorsodistally (see arrow, Fig. 22).

Legs (Figs 23-26). Lengths of legs: I 295-307, II 257-261, III 233-241, IV 307-309. Lengths of femora: I 60-63, II 49-52, III 48-53, IV 64-66; genua: I 44-45, II 42 -44, III 24-27, IV 31-34; tibiae: I 42-45, II 33-36, III 28-29, IV 36-38; tarsi: I 66-72, II 68-73, III 63-65, IV 88-91; ambulacra: I 21-25, II 21-22, III 19-20, IV 20-22. Chaetotaxy of leg segments I–IV normal for Zygoseius (sensu Halliday 1997): coxae 2-2-2-1, or I–III (0 0/1 0/1 0), IV (0 0/1 0/0 0); trochanters 6-5-5-5, or I (1 0/1 1/2 1); II (1 0/1 0/2 1), III–IV (1 1/1 0/2 0); femora 13-11-6-6, or I (2 3/1 2/3 2), II (2 3/1 2/2 1), III–IV (1 2/1 1/0 1); genua 13-11-8 or 9-9, or I (2 3/2 3/1 2), II (2 3/1 2/1 2), III (2 2/1 2/0 1 in one specimen, or 2 2/1 2/1 1 in another specimen), IV (2 2/1 3/0 1); tibiae 13-10-8-8, or I (2 3/2 3/1 2), II (2 2/1 2/1 2), III–IV (2 1/1 2/1 1); tarsi II–IV 18-18-18, all as 3 3/2 3/2 3 + md and mv. All setae on legs I–IV simple, relatively short and tapered, except: femur I with pd1-2 thickened, pd2 thicker (lengths: pd1 10-12, pd2 11-12); tarsi II–III with apical setae al1, av1, pv1, pl1 and subapical setae av2, pv2 and md short, spur-like; tarsus IV with setae al1, av1, pv1, pl1 and md short, spur-like; tarsi II–IV with mv longer and slightly slender. Trochanter III with small cuticular spur posterolaterally, and trochanter IV with two cuticular spur posterolaterally. Ventral surfaces of coxae II–IV and trochanters I–II, anterolateral surface of trochanter IV, and dorsal surfaces of femora and tibiae I–IV, genua and basitarsi II–IV with some sigillae. All ambulacra with a pair of well-developed hooked claws. Pulvilli not discerned.

Spermathecal apparatus (Plate 2). Spermatheca small, 6-8 wide, somewhat kidney-shaped, with no stalk, directly connected to a globular, large sperm reservoir (diameter 17-21), followed by a long spermatic canal (27-34 long). Sperm reservoir presenting a narrow central duct; spermatic canal with distinct walls, diverging basally.

Male and immature stages.

Unknown.

Material examined.

Holotype: Female. Mexico, Chiapas State, 6 miles NE of San Cristóbal de Las Casas, from flood debris in creek, 15 May 1969, coll. Evert E. Lindquist. Paratype: Female, same data as holotype. The holotype and paratype are deposited at the Canadian National Collection of Insects, Arachnids and Nematodes (CNC), Agriculture and Agri-Food Canada, Ottawa, Canada.

Etymology.

The species is named in honor of Evert E. Lindquist, for his invaluable endeavors on the systematics of Mesostigmata over the years. The specimens of this new species were collected by him.

Remarks.

The dorsal seta of trochanter I in Zygoseius papaver and Zygoseius lindquisti is inserted in a posterior position. We herein call this seta d (Figs 10, 23), although in the chaeto tactic formula, we indicated it as posterodorsal, given its clear posterior position, as in Halliday (1997). Evans (1963a, fig. 1i) indicated ‘ad’ for this dorsal seta, as illustrated for Pergamasus ( Parasitidae ). In the text, however, he called it ‘d’, for Pergamasus and for other gamasines. We have examined adult specimens of other Zygoseius spp., as well as of Pachylaelaps ( Pachylaelapidae ), Gaeolaelaps ( Laelapidae ), Asca ( Ascidae ), Proctolaelaps ( Melicharidae ), Parasitus and Pergamasus ( Parasitidae ), and the dorsal seta of trochanter I was usually inserted in a slightly to moderately posterior position, and rarely on the mediodorsal line or in a (slightly) anterior position.

In his diagnosis of the genus Zygoseius , Halliday (1997) indicated one pv and one pl setae on trochanter IV, whereas Evans (1963a) indicated two pv and no pl (as we did, herein). Indeed, pv1 is inserted much more posteriorly than pv2 (although not necessarily posterolaterally), and this situation is similar to that of pv1-2 of trochanters II–III ( Evans 1963a; Figs 11-13, 24-26).

In addition to poroid idR3, between setae R3 and R4, the soft opisthogastric cuticle has a sclerotized complex of two pore-like structures, posterolaterad the peritre matal-metapodal shield. These structures may be two openings of the same underlying gland complex; alternatively, they may be a gland opening and an associated poroid (note that both of these structures are sometimes visible in lateral view when the soft cuticle is folded, instead of the normal ventral view). It is unclear whether this gland opening is homologous to the one (gp) typically found in the poststigmatic region of peritrematal shields in many Mesostigmata (e.g. Lindquist and Moraza 2016). This double pore-like structure also occurs in Zygoseius papaver sp. n., as well as in Zygoseius ampullus and Zygoseius metoecus ( Halliday 1997), and Zygoseius sarcinulus (AA, personal observations).

Zygoseius lindquisti sp. n. shares certain morphological features with Zygoseius incisus Karg, 1998 and Zygoseius margaritatus Karg & Schorlemmer, 2009, including: (1) an epistome with two thin projections, about twice as long as distance between their bases, sparsely serrated, mostly in apical half; (2) the ratio J4 setae inserted well farther apart from each other than J1 setae (ratio of distance J4 –J4/J1– J1= 1.42-1.57 in Zygoseius lindquisti sp. n.); (3) J1-2 setae slightly shorter than distance between insertions of J1 and J2 (length J1-2 setae/J1-2 distance= 0.8-0.9 in Zygoseius lindquisti sp. n.); (4) ventrianal shield with short setae, including JV1-2; (5) the length of seta Z5 (20-26 in Zygoseius lindquisti sp. n.). It also has a spermathecal apparatus similar to Zygoseius margaritatus , although the latter has a more elongate, egg-shaped spermatic reservoir followed by a spermatic canal more constricted distally. The spermathecal apparatus of Zygoseius incisus is distinct, with a narrow elongate spermatic canal. The species Zygoseius lindquisti sp. n. can further be distinguished from the two species by (1) the dense micropunctation on its dorsal, sternal and genital shields, and its ventrianal shield lineate anteriorly and reticulate laterally and posteriorly; (2) its relatively broad dorsal shield (396-413 long, 278-283 wide; vs 430 long, 260 wide in Zygoseius incisus , 336-392 long, 231-256 wide in Zygoseius margaritatus ); (3) its relatively wide ventrianal shield (153-154 long, 189-196 wide; vs. 160 long, 170 wide in Zygoseius incisus , 140 long, 182 wide in Zygoseius margaritatus ); (4) many longer setae in the opisthonotal region (e.g. J1, J4, S5).

The new species also has a spermathecal apparatus similar to Zygoseius furciger . Based on the two females examined, however, Zygoseius lindquisti sp. n. has a sperm reservoir globular with enlarged spermatic canal throughout, whereas the sperm reservoir of Zygoseius furciger ranges from globular to oval with spermatic canal constricted distally (in proximity to sperm reservoir). The detailed description of Halliday (1997) allows to easily distinguish the new species from Zygoseius furciger , by (1) its sternal shield faintly lineate and densely micropunctate (reticulate and with punctae along cell margins in Zygoseius furciger ); (2) smaller dorsal shield (396-413 long; vs 418-518 in Zygoseius furciger ); (3) some setae in opisthonotal region slightly longer (e.g. J1, J4); (4) hypostomal setae h1 and h3 subequal in length (h3 about 1.5 × as long as h1 in Halliday, 1997); (5) deutosternum with 6-7 rows of denticles (eight rows in Zygoseius furciger ).