Sessiluncus aegypticus Nasr & Afifi, 1986

Kazemi, Shahrooz, Nasr, Abdelrady Korashy, Ramadan, Mahmoud Mohamed & Klompen, Hans, 2021, Review of the genus Sessiluncus (Acari: Mesostigmata: Ologamasidae), description of male and redescription of female of Sessiluncus aegypticus, and notes on some morphological characters of the genus, Zootaxa 5061 (2), pp. 271-299 : 278-283

Sessiluncus aegypticus Nasr & Afifi, 1986

Sessiluncus aegypticus Nasr & Afifi, 1986: 18 .

Sessiluncus aegypticus .—Zaher 1986: 31; Rajaei et al. 2012: 412; Kazemi & Rajaei 2013: 125; Castilho et al. 2016: 100 ; Alatawi et al. 2018: 384 .

Diagnosis (female and male). Dorsal shield with 37 pairs of short setae; glandular opening gd8 absent, gd9 present. Presternal platelets free, though abutting sternal shield. Sternal seta st1 barbed, other sternal setae smooth and shorter than st1. Ventrianal shield slightly longer than wide. Poststigmatic region of peritrematal shield well developed, wide, obliquely truncate, reaching beyond posterior level of coxa IV. Peritreme straight, extending to anterior level of coxa II. Corniculus without inner tooth. Setae h1–h3 and pc barbed. Lateral transverse ridges connected to deutosternal groove smooth. Movable and fixed digits of chelicera in female with three and four teeth, respectively, and with two and five teeth in male. In female, trochanter II with a small projection posterolateral dorsally; femur III with a small rounded ventral projection; trochanter IV with three anterolateral projections, including one large dorsal projection and two smaller ones ventrally, and one large posterolateral spur-like projection. Male with large spur-like seta av on femur II; seta av on genu and tibia II knob-like, but av on tibia II with a sharp apex; femur III with one large ventral cuticular spur.

Description. Adult male (n=2) ( Figures 1–8 , 10–12 , 25–27 , 29 , 37 )

Dorsal idiosoma ( Figures 1 , 25 ). Dorsal shield suboval, 473–494 long, 279–292 wide, anterior region of shield somewhat truncate, with a blunt, somewhat serrate, protrusion on each anterolateral shield corner, flanking either a narrow sclerotised strip anterior to dorsal shield ( Figures 1 , 3 ) or a series of narrow discrete platelets ( Figure 9 ). Dorsal shield covering entire dorsal idiosoma and slightly extending ventrally posterolaterally, reticulate throughout, except for anteromedian area between setae j1–j4 and area posterior to seta J4; with 37 pairs of short setae: j1 (32– 35), j2 (31–34) and Z5 (27–29) barbed, z2, z4, s2, s4 smooth (26–29), others 18–25 long, mostly smooth; shield with 17 pairs of poroids, including id1–id2, id4–id6, idm1–idm6, idl1–idl4, is1, idx; in addition to one pair of pcs between idm2 and idm3; four pairs of gland pores (gd1, gd5, gd6, gd9).

Ventral idiosoma ( Figures 2 , 26–27 ). Tritosternal base trapezoidal, short, 22–24 long, 22–24 wide at base and 9–10 wide at apex, sparsely pilose laciniae free, 48–51 long. One pair of presternal platelets well sclerotised, free, flanking base of tritosternum. Sternal shield reticulate throughout, 179–184 long, 110–115 wide, fused to endopodal platelets between coxae I–IV and also fused to continuous exopodal strip anteriorly via the endopodal shield between coxae I–II (area bearing gland pores gvb) and posteriorly via the parapodal shield behind coxae I–IV; male genital opening in anterior region of shield, anterior margin of shield irregularly straight, with two small lateral processes flanking presternal platelets, posterior margin of shield straight; shield with five pairs of setae, st1 (36–38) barbed and longest, st2 (31–33), st3 (26–29), st4 (27–28) and st5 (25–26) smooth, and three pairs of poroids (iv1–iv3); setae st2 (79–85) farther apart than pairs of st1 (62–65), st3 (68–76) and st4 (65–74). Ventrianal shield 202–208 long, 207–211 wide, reticulate throughout except for smooth posterior area around anal opening, bearing six pairs of opisthogastric setae and circumanals: Jv1–Jv3 smooth (22–25), Zv1 (26–28) and Zv2 (20–23) barbed, Zv3 smooth (26–28), para-anal (pa) (22–23) and postanal (ps) (24–26) setae barbed, with four pairs of poroids, including iv5 and four pairs of ivo; cribrum narrow, with minute spicules, narrowly extending laterally to level of postanal seta ( Figure 27 ). Opisthogastric soft cuticle with two pairs of setae Jv4 (20–22) and Jv5 (24–25), and three pairs of poroids, idRp, ivo and ivp. Peritrematal shield well developed laterad peritreme, anteriorly fused to dorsal shield and posteriorly free; with two crenate protrusions on lateral margin of shield, at posterior level of coxa II and anterior level of coxa III ( Figures 2 , 26 ), bearing one gland pore between crenate projections and one poroid anteriad anterior crenate projection, in addition to one gland pore anterior to the tip of peritreme; poststigmatic shield region slightly wider, obliquely truncate, extending beyond posterior margin of coxa IV, with one poroid and one moderately large gland pore ( Figure 26 ). Peritreme more or less straight, extending to anterior level of coxa II.

Gnathosoma ( Figures 3–4 , 29–30 ). Anterior margin of gnathotectum with a median triangular projection, flanked by two shorter acute projections, and sometimes with 1–2 denticles in between ( Figures 3 , 29 ). Labrum triangular and finely fringed, almost reaching anterior apex of corniculus; with one pair of denticulate paralabra near the base of the labrum; a long directed stylus arising anteriorly from each paralabrum, laying beneath the labrum and extending to anterior labrum tip. Corniculus horn-like; internal malae with a pair of narrow, long and smooth median projections, flanked by oblique, densely fringed margins; subcapitular setae barbed, h1–h3 subequal, 24–29 long, longer than pc (19–20); deutosternal groove with nine denticulate rows: most anterior row convex to subtriangular, second row straight to slightly concave, both with similar width, third row with markedly larger teeth only medially, fourth to seventh rows with same width and usually bearing minute sparse denticles, eighth row narrower, with distinct teeth, ninth row narrow, as wide as third row, and groove ending by a smooth ridge; with smooth lateral transverse ridges connected to deutosternal groove posteriorly. Second segment of chelicera stout, 152–159 long, including fixed digit (72–74 long), bearing four teeth, distalmost tooth minute, pilus dentilis short, setiform; movable digit of chelicera almost half as long as second segment of chelicera, 74–76 long, with three teeth; dorsal cheliceral seta setiform, smooth; dorsal and antiaxial poroids distinct ( Figures 4 , 30 ). Palp length 164–172; palp chaetotaxy 2-5-6-14-15; setae on trochanter, femur and genu slightly pilose in apical half, setae al on femur and al1 on genu densely barbed in apical half, d2 on femur and pl on genu smooth, al2 on genu apically blade-like, all setae on tibia and tarsus smooth, except al on tibia slightly pilose; palptarsus apotele 3-tined.

Legs ( Figures 5–8 , 10–12 , 37 ). Tarsus I with four relatively long subapical setae; ambulacrum I sessile, sheath broadly fused to tarsus and only long enough to contain retracted claw complex ( Figure 5 ); legs II–IV each with three small apicoventral projections on tarsus, and relatively long ambulacral stalk, 34–40 long ( Figures 10–12 ). Length of legs: I 488–507, II 361–391, III 301–326, IV 409–426. Lengths of femora I 103–115, II 70–76, III 65–73, IV 88–94; genua I 68–72, II 54–62, III 41–44, IV 56; tibiae I 79–83, II 62–68, III 41–47, IV 62–65; tarsi I 138–144, II 97–100, III 79, IV 103–106. Setation of legs I–IV normal for the genus, genu IV with one seta pl (2, 2/1, 3/0, 1). Leg setae simple, mostly slightly pilose, relatively short to moderately long. Modified setae ( Figure 37 ): av on femur II as a large spur ( Figure 6 ); av on genu and tibia II knob-like, av on tibia apically tapered ( Figure 7 ). Femur III with a large ventral cuticular spur ( Figures 8 , 37 ).

Figures

FIGURE 2. Sessiluncus aegypticus Nasr & Affifi, male, ventral idiosoma.

of the species, but they stated 7 pairs in the text. We herein referred to their illustration (page 722, figure 1A). 2 Based on Bhattacharyya (1965), one ventral seta on genu and tibia

FIGURES 3–9. Sessiluncus aegypticus Nasr & Affifi, 3–8. Male; 9. Female. 3. Gnathotectum, followed posteriorly narrow sclerotised band; 4. Chelicera; 5. Tarsus I; 6. Femur II; 7. Genu–tibia II; 8. Femur III; 9. Gnathotectum, followed posteriorly narrow sclerotised band (in specimen from Iran).

FIGURES 10–12. Sessiluncus aegypticus Nasr & Affifi, male. 10. Tarsus II; 11. Tarsus III; 12. Tarsus IV.

FIGURES 25–26. Sessiluncus aegypticus Nasr & Affifi, female. 25. Dorsal idiosoma; 26. Ventral idiosoma.

FIGURES 27–28. Sessiluncus aegypticus Nasr & Affifi. 27. Male, ventrianal shield; 28. Female, sternal region.

FIGURES 29–36. Sessiluncus aegypticus Nasr &Affifi.29. Male, gnathotectum; 30. Male, chelicera; 31. Female, subcapitulum (inset); 32. Female, dorsal (inner) view of hypostom; 33. Female, palp; 34. Female, chelicera; 35. Female, trochanter IV; 36. Female, femur III. Abbreviations: lb, labrum; plb, paralabrum.

FIGURES 37–40. 37. Sessiluncus aegypticus Nasr & Affifi, male, modified seta and spur on legs II & III, respectively; 38– 40. Sessiluncus hungaricus, female. 38. Dorsal shield, posterolateral region; 39. Sternal shield, and posterior horse-shoe-like extension of the shield (inset); 40. Peritrematal shield and antrolateral part of ventrianal shield.