Opilioseius grallator, Lindquist, Evert E. & Moraza, Maria L., 2010

Lindquist, Evert E. & Moraza, Maria L., 2010, Revised diagnosis of the family Blattisociidae (Acari: Mesostigmata: Phytoseioidea), with a key to its genera and description of a new fungus- inhabiting genus from Costa Rica, Zootaxa 2479, pp. 1-21 : 15-18

Opilioseius grallator new species

( Figs 1–29 , 32–35 , 39, 40 )

Diagnosis. With the attributes of the genus. In addition, dorsal shield with setae z2, z5, j6 nearly as short as clunal setae J5, with s5 the longest, over half as long as dorsal shield, and with Z3 and Z4 subequally next longest, slightly longer than Z5; peritremes reaching only to level of setae z4; coxa II with seta av minute; leg IV with greatly elongated setae on genu (pd -1), tibia (ad -1), basitarsus (ad -4), and telotarsus (ad -3).

Description. ADULT FEMALE. Dorsal shield 290-350 long, 165–200 at its greatest width at level of setae r3; shield smooth, unornamented over entire surface ( Fig. 12 ); with 23 pairs of attenuated, mostly smooth setae, except J5 and few of longest setae sparsely, almost imperceptibly barbed basally. Dorsal setae of greatly different lengths, J5 shortest (4–6), z2, z5, j6 nearly as short (7–12), j1 moderately short (25–30), s5 longest (193–220), Z3 (125–145) and Z4 (125–138) subequally next longest, followed by Z5 (105–115), r3 (88–100), j5 (55–68); other setae of different moderate lengths (27–58) ( Fig. 12 ). Lateral soft cuticle with three pairs of simple r -R marginal setae (30–55). Peritrematal plates uniting with dorsal shield anteriorly at level of setae s1; peritremes shortened, reaching anteriorly to level of setae z4.

Tritosternum ( Fig. 5 ) with base twice as long (23–28) as wide, with laciniae free for about 0.8 of total length (70–79 excluding base), their fused area with a chevron of denticles. Presternal area with pair of weakly sclerotized plates consolidated with sternal shield ( Fig. 16 ). Sternal shield mid-lateral length from anterior edge of sternal/presternal margin to posterior margin 95–105, narrowest width 70–80, unornamented, weakly sclerotized; anterior margin deeply emarginate medially; lateral margins indented at level between lyrifissures iv1 and setae st2, and with weak endopodal extensions between coxae I–II and II–III; posterior margin slightly concave. Sternal setae st1-st4 of similar length (50–60), st4 on weakly sclerotized metasternal plates. Endopodal strips weakly developed between coxae III and IV. Epigynal shield 96-120 long, 80-95 wide at level of setae st5, unornamented, axe-shaped with truncate posterior margin and tapered, slightly concave lateral margins, with genital setae st5 (51–55) subequally as long as st1-st4. Paragenital poroids iv5 well removed on soft cuticle from posterolateral corners of epigynal shield. Ventrianal shield unornamented, smaller than epigynal shield, midlength 66–75, greatest width near convex anterior margin 55–65, with two pairs of opisthogastric setae JV2 (45-60), ZV2 (35–52), subequally short paranal (21–24) and postanal setae (18–20), and gland pores gv3 ( Fig. 16 ). Soft cuticle with six pairs of opisthogastric setae JV1 (40–43), ZV1 (40–45), ZV3 (24–30), JV4 (65–72), ZV4 (38–42), JV5 (80–87), flanked by posteriormost pair of marginal R setae. Peritrematal shield slightly wider than stigma at that level, bearing three poroids, three gland pores, and consolidated with slender exopodal strip curving behind coxa IV ( Figs 15, 16 ). Spermathecal apparatus with long (40–42), slender, thinly sclerotized calyx, and a minor duct arising from embolus near base of calyx, seeming to adhere to calyx wall and ending amidst folds of highly plicate and expandable vesicle ( Figs 14 a– b).

Gnathotectum with anterior margin irregularly convex to nearly truncate, denticulate ( Fig. 11 ). Cheliceral shaft, excluding basal section, 85–87 long, with stout digits; dorsal face of fixed digit with blunt protuberance at base of short, basally thick, dorsal seta ( Fig. 10 ); fixed digit with minute (1.5–2.0) pilus dentilis, with row of 9 or 10 coarse teeth along entire masticatory surface and offset subapical tooth ( Figs 8, 10 ); movable digit (30–35) with row of 5 or 6 similarly coarse teeth along apical half of masticatory surface, followed basally by series of several indentations that accommodate more basal teeth of fixed digit; movable digit with two paraxial grooves running proximally and ventrally, one on apical third, leading from base of subapical tooth, one on mid-third, leading from base of second tooth ( Figs 8, 9 ). Corniculi with medial edges and pointed apices well separated but parallel; internal malae slightly longer than corniculi ( Fig. 1 ). Deutosternum with anterior five rows of denticles each with 5-7 fine teeth, the first, third and fifth rows flanked by arched denticulate extensions ( Fig. 1 ), sixth and seventh rows widened, multidenticulate. Subcapitulum with lateral hypostomatic setae hp2 subequally as long as anterior pair hp1 (25–30); medial pair hp3 longer (30–35), basal pair pc longest (39–42). Palpal length 105–110, not elongated. Palptrochanter setae slender, inner seta slightly longer than outer one; palpfemur with seta pl (30–35) the longest of palpal setae, and with seta al spatulate, with flat tip; palpgenu with setae al -1 and al -2 spatulate, with rounded tips ( Figs 6, 7 ).

Legs IV the longest (810–875, excluding pretarsus) of legs, about 2.4-2.7 as long as dorsal shield ( Fig. 39 ); other leg lengths: I 705–730, II 458–490, III 498–540. Legs II, III, IV with tarsus 3.2–3.7, 3.9–4.1, 3.6– 3.7 times, respectively, as long as tibia. Tarsi II–IV with pair of apical setal processes ad -1, pd -1 minute (8– 10), less than 0.2 the length of pretarsus to base of claws (50–55 for II-III, 80–85 for IV) ( Fig. 21 ). Leg I segment length ratios, femur: genu: tibia: tarsus, about 1.0: 0.8: 0.95–1.0: 2.0–2.1; tarsus (265–268) longer than femur (125–139), genu (100–111), and tibia (123–130); length of pretarsus I to base of claws 20–26. Coxae II–IV each with a raised boss on ventral surface ( Fig. 16 ); coxal setae simple, moderately long (30–40), except coxa II av short (5–6). Legs I to IV with chaetotactic formulae of segments as described for genus. Legs I and II ( Figs 17, 18 ) without notably long setae, except tibia I ad -3 (52–60) and basitarsus II ad -4 (38– 45) slightly elongated; genu I setae pd -2, pd -3 with blunt bent tips, stouter and shorter (17–20) than neighboring ad setae. Leg III with tibial ad -1 (42–50) and pd -2 (55–72) somewhat elongated ( Fig. 19 ), and basitarsal ad -4 slightly so. Leg IV with femoral setae v and al -1 somewhat elongated (60–70), v stiff, aligned proximal to al - 1 in an anterolateral position ( Fig. 20 ); genual seta pd -1 (235–260) and tibial seta ad -1 (220– 280) greatly elongated, tibial pd -1 (80–85) slightly so; basitarsal seta ad -4 (212–242) and telotarsal seta ad -3 (202–225) greatly elongated, basitarsal pd -4 (95–100) slightly so ( Fig. 21 ).

ADULT MALE. Dorsal shield 224–290 long, 185-200 at its greatest width at level of setae r5; shield form, ornamentation, and setation as in female except more expanded anterolaterally so as to bear setae r5 and to be more broadly united to peritrematal shields at level of setae r3 ( Fig. 32 ). Form and proportionate size of dorsal shield setae as in female, except setae collectively about 15-20 percent shorter, e. g., z2, z5, j6 (5–10), s5 (153– 162), Z3, Z4 (100–105), Z5 (68–70), r3 (73–80), j5 (40–52). Lateral soft cuticle without any R -marginal setae. Peritremes as in female, reaching anteriorly to level of setae z4-s4.

Tritosternum as in female, including chevron of denticles on fused basal portion of laciniae. Ventral shields unornamented, as in female. Sternitigenital shield mid-lateral length 132–140, width 80 at level between coxae II, with five pairs of setae of similar lengths (40–47) and two pairs of poroids; lateral margins slightly indented between coxae II, deeply incised between bases of setae st3 and st4, and again behind st4, partly delineating metasternal and genital portions of shield ( Fig. 33 ). Endopodal strips alongside coxae II–III and III–IV weakly developed, free from sternitigenital shield. Ventrianal shield mid-length (70–75), greatest midlateral width (83–94) at level of setae JV2, with irregularly convex lateral margins, bearing the only four pairs of opisthogastric setae present, JV1, ZV2, JV2, JV5 plus the circumanal setae; form and relative size of these setae as in female, but collectively about 25 percent shorter. Metapodal plates indiscernible.

Gnathotectum ( Fig. 28 ) similar to that of female. Cheliceral fixed digit with minute pilus dentilis and row of 6-8 coarse teeth ( Fig. 25 ); movable digit (27–28) with two or three teeth, or these are indentations to receive some of apposed teeth of fixed digit; spermatodactyl a complex structure, which in dorsoventral view seems to have a pointed spearlike process (21) covering the twisted apex of the main dactyl shaft (length 16 to concave apex) that bears the sperm transfer tube ( Figs 25–27 ). Corniculi (28–29) more slender and widely spaced basally, with their apices more flared than in female; internal malae slightly longer and more acute apically than in female ( Fig. 29 ). Subcapitulum with rows of deutosternal denticles and relative lengths of setae as in female. Palpal structures similar to those in female.

Relative leg lengths, excluding pretarsi, similar to those of female, I (607–616), II (397–410), III (434– 446), IV (695–744). Leg I segment length ratios, leg coxal structures and setae (including short av on coxa II and slightly spinelike pd-2 and pd-3 on genu I), and relative leg setal lengths as in female except setae collectively about 15–25 percent shorter.

DEUTONYMPH. Dorsal shield weakly sclerotized, 261 long, 148 at its greatest width at level of setae s5; shield without discernible lateral incisions, its form and setation as in female except less expanded anterolaterally so that setae s1 and r3 on soft cuticle, and anterior apices of peritrematal shields ending freely ( Fig. 34 ). Form and proportionate size of dorsal shield setae as in female, except setae collectively about 15- 20 percent shorter. Lateral soft cuticle with four pairs of marginal setae, r3, r5, R4, R5. Peritrematal shield a thin strip, reaching anteriorly to level of setae st1, and extending posteriorly from stigma only to bear poroid ip3 and gland pore gp3; peritreme reaching anteriorly to mid-level of coxae III.

Tritosternum as in female, including chevron of denticles on fused basal portion of laciniae. Intercoxal shield so poorly sclerotized that its delineation hardly perceptible, with four pairs of setae and two pairs of poroids, st1-st3 of similar lengths (38–44), st4 shorter (26), poroids iv3 absent; setae st5 (35) on soft cuticle ( Fig. 35 ). Endopodal strips alongside coxae II-III developed, fused to intercoxal shield. Anal shield weakly sclerotized, oval (its anterior margin folded on specimen at hand), midlateral width (52) at level of setae ZV2; paranal setae slightly longer than postanal seta. Eight pairs of opisthogastric setae on soft cuticle, ZV3, ZV4, shortest, JV5 longest. Metapodal plates indiscernible.

Gnathotectum, chelicerae, subcapitulum, and palpal structures as in adult female.

Relative leg lengths, excluding pretarsi, I (527), II (377), III (453), IV (615); pretarsi, I (28), II-III (41), IV (70). Leg I segment length ratios, leg coxal structures and setae (including short av on coxa II), and relative leg setal lengths as in adult female except setae collectively about 25–30 percent shorter.

Type material. All specimens from samples collected on the area of the La Selva Biological Station, Heredia Province, COSTA RICA (10° 26' 1" N, 84° 1' 2" W, elevation 50–150 m): HOLOTYPE: adult female, 150 m along Surá trail, ex “Hongo” (fungus), 21 February 1995, coll. ALAS. PARATYPES: 9 adult females, with same data as holotype; 8 adult females, 4 adult males, with same data as holotype except fungus determined as Coriolopsis , and coll. E.E. Lindquist; 1 adult female, 1 deutonymph, with same data as holotype except 9 March 1995; 1 adult female, Arboleda area, ex Hongo, 28 March 1995, coll. ALAS; 2 adult females, 645 m along Suampo trail, ex fungus, 18 April 1995, coll. ALAS; 2 adult females, 345 m along Holdridge trail, ex fungus, 18 April 1995, coll. ALAS; 5 adult females, ca 300 m along Occidental trail, ex polypore fungi on canopy-shaded log, 13 November 1992, coll. E.E. Lindquist.

Etymology. The specific epithet, grallator , is masculine and based on the Latin “ gralla ”, meaning “stilt”, and indicates “one that walks on stilts”.

Remarks. Resembling minute opilionid-like creatures ( Fig. 39 ), these spindly-legged mites move slowly along the undersurfaces of the fungal fruiting bodies (sporocarps), which consist of a series of parallel laminae. The apices of all six of legs II to IV invariably rest on the tips of the laminae, like tiny feet on the joists of a subflooring. In feeding, they protrude their gnathosoma down between the laminae, without taking legs III–IV off the tips of the laminae. Whether they feed on fungal matter or on some of the various microarthropods (other mites, springtails, tiny beetles) that move between the laminae, was not ascertained (R.K. Colwell, personal observations, 13 March 1995).

Full-sized eggs within adult female Opilioseius grallator are remarkably large relative to the female’s idiosoma ( Fig. 40 ). Maximum length of eight eggs ranged from 250 to 300 µm, and were 0.74 to 0.85 the maternal females’ dorsal shield lengths of 312 to 337 µm, bearing in mind that the dorsal shield is fully developed, extending from just anterior of the vertical setae j1 to just posterior to the clunals J5. Females have an abundance of soft pliable cuticle between the dorsal and ventral shields, and a small ventrianal shield, which permit considerable idiosomatic expansion to accommodate such large eggs. One slide preparation of a female in lateral view shows a tremendous dorsoventral opisthosomatic distension that accommodates the greatest length of the egg at vertical right angles to that of her idiosoma, thus orienting the smallest egg dimension (width) for issue from the genital opening. Subsequent oviposition of such large eggs, whose greatest widths range from 192 to 210 µm, through a genital orifice whose width between the coxae of legs IV appears to be 130–150 µm, must depend on considerable egg flexibility and resilience (see Evans 1992), as there is no evidence of maternal idiosomatic rupture. Few data are available in the literature concerning this aspect of egg size among free-living mesostigmatic mites. Fully adequate metric data for egg size, i.e. egg mass or volume compared to adult female mass or volume, are not available. However, egg length/dorsal shield length ratios of 0.48 to 0.57 are evident in the phytoseiids Typhlodromalus peregrinus (Muma) and Phytoseius hawaiiensis Prasad , a family with relatively large egg sizes ( Muma 1969; Sanderson & McMurtry 1984). A similar ratio of 0.45 to 0.48 is evident from the mature, newly-laid egg length versus the maternal dorsal shield length of Blattisocius patagiorum Treat given by Treat (1966). Other than Opilioseius grallator , the relatively largest eggs we've encountered are one in a female of Zercoseius spathuliger Berlese with length ratio of 0.67, and those of two undescribed species of Aceodromus , with length ratios of 0.51 to 0.63 from Brazil and 0.60 to 0.70 from the La Selva area in Costa Rica, the highest ratio being from an obviously mature egg containing a pharate larva. We are unaware of any other non-parasitic mesostigmatans having a fully developed dorsal shield (i.e., bearing setae j1 to J5) that have such proportionately large eggs.

These stilt-legged mites coexist with a remarkable variety of other blattisociid mites occupying the same fungi. Although slide preparations and identifications were not made of any of the trombidiform or sarcoptiform (oribatid and astigmatan) mites that may occupy the same fungi, we have determined material of the following mesostigmatic taxa from just one of the several samples from which Opilioseius grallator was recovered: an undescribed blattisociid genus with one species (which we plan to describe next), 11 species of Lasioseius , four species of Cheiroseius , five species of Dendrolaelaspis , two species of Cosmolaelaps , and one each of Asca , Hypoaspis , Parasitus , and an undetermined (perhaps undescribed) genus of Veigaiidae . Of these 27 species, 16 were abundant (nine Lasioseius , three Cheiroseius , four Dendrolaelaspis ), indicating they were regular members of that particular bracket fungal guild.

Figures

FIGURES 1 – 11. Opilioseius grallator n. sp., adult female: 1, subcapitulum; 2 a – 2 b, corniculi; 3, two views of corniculus and salivary stylet, dorsal view; 4, paralabral processes; 5, tritosternum, showing denticulate chevron at base of laciniae; 6, palpus, dorsolateral view; 7, detail of seta al of palpfemur; 8, chelicera, lateral antiaxial view; 9 a, separate ventrolateral view of movable digit; 9 b, separate paraxial lateral view of movable digit; 10, separate paraxial view of fixed digit; 11, gnathotectum.

FIGURES 12 – 13. Opilioseius grallator n. sp., adult female: 12, idiosoma, dorsal aspect with detail of peritrematal shield; 13, enlarged separate views of dorsal setae denoted.

FIGURES 14 – 16. Opilioseius grallator n. sp., adult female: 14 a – b, detail of spermatheca showing minor duct arising from embolus at base of calyx; 15, detail of peritrematal shield, free from exopodal strip alongside legs II – IV except where they join at mid-level of leg IV; 16, idiosoma, ventral aspect with detail of glandular pores on coxa I.

FIGURES 17 – 22. Opilioseius grallator n. sp., adult female: 17 – 20, legs I-IV, excluding tarsi: 17, leg I, dorsal view; 18, leg II, posterolateral view; 19, leg III, posterolateral view; 20, leg IV, posterolateral view with detail of elongate setae on genu and tibia; 21, tarsus IV, dorsal view; 22 a – b, details of distal structures of tarsus IV: 22 a, ventroapical tarsal process below base of pretarsus, and distal minute tarsal setae ad - 1, pd - 1; 22 b, pretarsal claws, paradactyli and pulvillus.

FIGURES 23 – 31. 23 – 29, Opilioseius grallator n. sp., adult: 23, tarsus I, right leg, dorsal view; 24, tarsus I, detail of tarsal seta “ S ” and associated setae; 25 – 29, male: 25, chelicera, paraxial view; 26 a separate, lateroventral view of movable digit; 26 b, separate, lateroventral view of movable digit with scale over dentate region; 27 a spermatodactyl with ventral scale; 27 b, ventral cheliceral scale; 28, gnathotectum; 29, subcapitulum. 30 – 31, Podocinum sp., adult: 30, tarsus I, right leg, dorsal view; 31, tarsus I, detail of tarsal seta “ S ” and associated setae.

FIGURES 32 – 33. Opilioseius grallator n. sp., adult male: 32, idiosoma, dorsal aspect, with laterally expanded detail of peritrematal shield fused to podonotal dorsal region; 33, idiosoma, ventral view.

FIGURES 34 – 38. 34 – 35, Opilioseius grallator n. sp., deutonymph: 34, idiosoma, dorsal aspect; 35, idiosoma, ventral aspect. 36 – 38, leg III, tarsal apex and pretarsus, showing different forms of ventroapical tarsal processes and conjectured acrotarsal demarcation: 36, Adenoseius sp. (Sejidae), anterolateral view; 37, Euzercon sp. (Euzerconidae), ventral view; 38, Arctacarus rostratus Evans (Arctacaridae), ventral view. Abbreviation: acr mar, acrotarsal margin.

FIGURES 39 – 40. Opilioseius grallator n. sp.: 39, photomicrograph of adult female, dorsoventral habitus view; 40, photomicrograph of gravid adult female, showing relative size of fully developed egg and maternal idiosoma, dorsoventral habitus view.