Gaeolaelaps furcatus Joharchi & Ueckermann, 2021

Joharchi, Omid, Ueckermann, Edward A., Döker, Ismail, Khaustov, Vladimir A. & Hänel, Christine, 2021, Some free-living laelapid mites (Acari: Mesostigmata: Laelapidae) from Tristan da Cunha and Nightingale Islands, with description of a new species of Gaeolaelaps Evans & Till (Acari: Laelapidae) and the first afrotropical record of the genus Nidilaelaps Shaw, Zootaxa 5026 (2), pp. 271-285 : 275-279

Gaeolaelaps furcatus Joharchi & Ueckermann sp. nov.

( Figures 5–22 )

Type material: Holotype, female, Soggy Plain, Boggy drainage area in a “natural area” 37°14’S 12°29’W, 16 March 2005, alt. 2762 ft., C. Hänel coll., from peat moss (Plantae: Sphagnales : Sphagnum ). Paratypes, five females same data as holotype and six females, Soggy Plain, Boggy drainage area in a “natural area” 37°14’S 12°29’W, 16 March 2005, alt. 2762 ft., C. Hänel coll., from a bog grass, Scirpus sulcatus Elliott (Plantae: Cyperaceae ).

Diagnosis (adult female). Dorsal shield reticulate throughout, with 38 pairs of smooth setae, including two pairs of Zx setae, unpaired (Jx) and z3 setae absent; length of setae slightly increasing from anterior to posterior; shield with five pairs of discernible gland pores (gd1, gd5–6, and gd8–9). Sternal shield with reticulate ornamentation throughout, except central and posterior parts smooth (or faintly reticulated), ratio of shield length/width ≃ 0.78. Genital shield, with length/width ratio ≃ 2.35, with 7–8 cells posterior to inverted-V ridge. Anal shield well widened, with length/width ratio ≃ 0.72, distinctly broader than width of genital shield (≃ 1.5 times). Opisthosomal integument with eight pairs of smooth setae, peritremes relatively long, extending to mid-level of coxae I. Fixed digit of chelicera with six teeth, including an offset subapical tooth (gabelzhan) and movable digit of chelicera with three teeth. Tarsus IV with three (ad2, pd2, pd3) elongated setae, paradactyli on pretarsi (p.p) II–IV very elongated (see Fig. 18 ) and pulvillar lobe (p.l) well developed in shape of fork on ambulacra II–IV (see Fig. 18 ).

Description. Female (n=12) ( Figures 5–22 )

Dorsal idiosoma ( Figs 5 & 11 ). Idiosoma length 568–591, width 350–360 wide. Dorsal shield 568–591 long, 293–321 wide, shield distinctly reticulate ( Figs 5 & 11 ). Shield parallel-sided from r3 to level of S4, progressively tapering until S5, until rounded posteriorly and with 38 pairs of smooth setae: 21 pairs of podonotal setae (31–38), z3 absent, 17 pairs of opisthonotal setae (33–42), including two pairs Zx setae. Lengths of setae slightly increasing from anterior to posterior, j1 (27–29), z1 (22–24) shortest, and Z5 (58–61) longest, see Figures 5 & 11 . Shield with about 21 pairs of discernible pore-like structures, including 16 poroids (id1, id2, id4–id6, idm-idm6, is1, idx, idl1, idl3, idl4) and five gland openings (gd1, gd5–6, gd8–9), others indistinct, see Figures 5 & 11 .

Ventral idiosoma ( Figs 6 & 12–14 ). Tritosternum with paired pilose laciniae (83–90), fused basally (3–5), columnar base 33–35 × 18–23 wide; presternal area lightly sclerotised, punctate, with a few transverse curved lines, sternal shield length 127–135, maximum width 164–173, narrowest between coxae II (106–109), with reticulate ornamentation throughout, except central and posterior parts smooth (or faintly reticulated) ( Figs 6 , 12 & 13 ), posterior margin almost straight, anterior margin slightly concave, remnants of gland pores gv1 apparent near posterior shield margin; bearing three pairs of smooth setae (st1–3) (35–39), never reaching base of next setae, one pair of lyrifissures (slit-like) adjacent to setae st1, and a pair of poroids (oval) between st2 and st3. Metasternal setae st4 (31–33) and metasternal poroids located on soft integument; metasternal platelets absent. Endopodal plates between coxae I–II (bearing gland pores gvb) and II–III completely fused to sternal shield, endopodal plates III/IV elongate, narrow and curved. Genital shield tongue-shaped, slightly expanded posteriorly, past setae st5, length 198–205, maximum width 78–87, posterior margin rounded, surface reticulated with irregular, mostly longitudinal lines in anterior region, posteriorly with 7–8 cells enclosed behind an inverted-V shaped ridge; bearing a pair of simple setae st5 (28–31) ( Figs 6 , 12 & 13 ). Shield flanked by two pairs of minute, elongate paragenital platelets; paragenital poroids iv5 located on soft cuticle lateral to shield near seta st5. Anal shield widened (width ≃ 1.5 times the length), distinctly broader (≃ 1.5 times) than width of genital shield, rounded anteriorly, length 80–85, width 110–118, anterior half lineate-reticulate, para-anal setae and post-anal seta subequal in length (38–41), cribrum consisting of a terminal tuft with 3–5 irregular rows of spicules and a pair of anterior arms reaching level of posterior margin of anus ( Figs 6 & 12 ); anal gland pores (gv3) on anterolateral margin of anal shield. Soft opisthogastric cuticle with pair of oval metapodal plates (26–30 long × 6–10 wide), an additional small round metapodal platelet more medially (12–14 long × 2–4 wide) and eight pairs of smooth setae (Jv1–Jv5, Zv1–Zv 2, Zv4) (29–53), Zv1 (29–32) shortest, and Jv5 (50–53) longest and five pairs of poroids (four ivo & ivp). Exopodal platelets between coxae II–III subtriangular, those behind coxae III–IV narrow, elongate, abutting to parapodal platelets, never fused, parapodal platelets strip-like, extending narrowly behind coxae IV and surrounding coxa IV ( Fig. 6 ). Peritrematal shield well developed, bearing one gland pores (gd3) and one poroid (id3) at level near coxae II–III, poststigmatic extension of shield with two pairs of poroids (id7 & ip) and one pair of gland pores (gp) ( Figs 6 & 14 ); anterior region of peritrematal shield fused to anterior margin of dorsal shield behind setae z1 ( Fig. 11 ). Peritremes relatively long, extending to mid-level of coxae I ( Fig. 6 ).

Gnathosoma ( Figs 7–10 & 15–17 ). Epistome convex and irregularly denticulate ( Fig. 8 ). Hypostomal groove with six transverse rows of denticles, each row with 20–30 tiny denticles, with smooth anterior and posterior transverse lines ( Figs 7 & 15 ). Hypostome with four pairs of smooth setae, h3 (43–46)> h1 (37–39)> pc (30–32)> h2 (29–31) ( Fig. 7 ). Corniculi robust and horn-like, extending slightly beyond palptrochanter. Supralabral process with tri-tined apicoventral projection ( Fig. 9 ). Internal malae with one pair of smooth median projections, flanked by lobes with fimbriate anterior margin; labrum with pilose surface ( Fig. 7 ). Chaetotaxy of palps ( Fig. 16 ): trochanter 2, femur 5, genu 6, tibia 14, tarsus 15, all setae smooth; palpfemur with seta d3 thickened and al paddle-like; palpgenu with al1 stout, blunt, al2 thickened and apically club-shaped; palp tarsal apotele two-tined ( Fig. 16 ). Fixed digit of chelicera with an offset distal tooth (gabelzhan), followed by five variously sized teeth, a setaceous pilus dentilis, dorsal cheliceral seta prostrate, arthrodial membrane with a rounded flap and normal filaments; cheliceral dorsal and lateral lyrifissures distinct; movable digit with three teeth, two small distal teeth followed by a large proximal tooth ( Figs 10 & 17 ).

Legs ( Figs 19–22 ). Legs II (415–420) and III (370–384) short, I (553–563) and IV (535–545) longer. Chaetotaxy normal for free-living Laelapidae : Leg I ( Fig. 19 ): coxa 0–0/1, 0/1–0, trochanter 1–0/1, 1/2–1 (pd slightly thickened), femur 2–2/1, 3/3–2 (pd2 & pd3 thickened), genu 2–3/2, 3/1–2, tibia 2–3/2, 3/1–2. Leg II ( Fig. 20 ): coxa 0–0/1, 0/1– 0, trochanter 1–0/2, 0/1–1, femur 2–3/1, 2/2–1 (pd2 thickened and slightly longer than others), genu 2–3/1, 2/1–2, tibia 2–2/1, 2/1–2. Leg III ( Fig. 21 ): coxa 0–0/1, 0/1–0, trochanter 1–1/2, 0/1–0 (ad slightly thickened), femur 1–2/1, 1/0–1 (all dorsal setae slightly thickened), genu 2–2/1, 2/1–1, tibia: 2–1/1, 2/1–1 (pd2 slightly thickened). Leg IV ( Fig. 22 ): coxa 0–0/1, 0/0–0, trochanter 1–0/2, 0/1–1, femur 1–2/1, 1/0–1 (all dorsal setae slightly thickened and inserted on small tubercles), genu 2–2/1, 3/0–1, tibia 2–1/1, 3/1–2 (all ventral setae thickened). Tarsi II-IV with 18 setae (3– 3/2, 3/2–3 + mv, md); with some ventral and lateral setae thickened, see Figures 20–22 . On tarsus IV ad2 (63–67), pd2 (82–85), pd3 (58–62) elongated. All pretarsi with well-developed paired claws, paradactyli on pretarsi II–IV very elongated (see Fig. 18 ) and pulvillar lobe well developed in shape of fork on ambulacra II–IV (see Fig. 18 ).

Insemination structures. Not seen, apparently unsclerotised.

Etymology. The name furcatus (Latin furcatus , forked) refers to the fork-shaped appearance of pulvillar lobes on ambulacra II–IV.

Differential diagnosis. The new species is unique within Gaeolaelaps by paradactyli on pretarsi II–IV very elongated (see Fig. 18 ) and pulvillar lobe well developed in shape of fork on ambulacra II–IV. The former character state is shared with the recently described species from Russia, G. euparadactylifer Joharchi, 2021 (in Joharchi et al., 2021). However, the new species can easily be distinguished from G. euparadactylifer by having long peritremes, extending to mid-level of coxae I (versus peritremes short, reaching to mid-level of coxae II in G. euparadactylifer ). Anal shield usually small, inversely pear-shaped or subtriangular, rarely rounded and wider than long, even wider than width of genital shield like in the new species with a length/width (= L/W) ratio of 0.7 at the broadest level and distinctly broader (≃ 1.5 times) than width of genital shield. The only known Gaeolaelaps species with nearly similar character states are Gaeolaelaps eupygidialis ( Karg, 2003) , G. transversanalis ( Karg, 2000) and G. orbiculatus Nemati & Mohseni, 2013 . Gaeolaelaps furcatus differs from G. eupygidialis , G. transversanalis and G. orbiculatus by having 38 pairs of dorsal setae (z3 absent), fixed and movable digits of chelicera with six and three teeth, respectively, versus all these three species with 39 pairs of setae on dorsal shield (z3 present), and chelicera with two teeth on movable digit and more than six teeth in G. eupygidialis , G. transversanalis and four teeth in G. orbiculatus on fixed digit. Gaeolaelaps furcatus resembles G. kargi ( Costa, 1968) and G. praesternalis ( Willmann, 1949) , due to the dorsal shield having 38 pairs of setae (z3 absent) and long peritremes extending to coxa I. Gaeolaelaps furcatus differs from them by having larger size of body (568–591) and tarsus IV with three elongated setae, while in G. kargi and G. praesternalis size of body much smaller (less than 460), tarsus IV with two elongated setae in G. kargi and without elongated setae in G. praesternalis . Dorsal shield setae relatively long in G. kargi , some of them reach to the base of next setae, while in Gaeolaelaps furcatus dorsal shield setae relatively shorter and none of them reach base of next. Gaeolaelaps nolli ( Karg, 1962) may be similar to Gaeolaelaps furcatus Joharchi & Ueckermann in general appearance, but G. nolli has a short peritremes nearly extending to mid-level of coxae II. Overall Gaeolaelaps furcatus can be easily distinguished from all other members of Gaeolaelaps by the following combination of characters: (1) dorsal shield oval shaped and with 38 pairs of setae (z3 absent) ( Figs 5 & 11 ); (2) peritremes long, reaching to mid-level of coxae I; (3) tarsus IV with three noticeably long setae (macrosetae) (ad2, pd2, pd3); (4) paradactyli on pretarsi II–IV well elongated (see Fig. 18 ) and pulvillar lobe well developed in shape of fork on ambulacra II–IV (see Fig. 18 ); (5) anal shield widened, wider than length, distinctly broader than width of genital shield (≃ 1.5 times) ( Figs 6 & 12 ) (6) fixed digit of chelicera in female with six teeth ( Figs 10 & 12 ); (7) movable digit with three teeth, two small distal teeth followed by a large proximal tooth ( Figs 10 & 12 ).

Figures

FIGURES 5–10. Gaeolaelaps furcatus Joharchi & Ueckermann sp. nov., female. 5, dorsal idiosoma; 6, ventral idiosoma; 7, subcapitulum; 8, epistome; 9, supralabral process; 10, chelicera.

FIGURES 11–18. DIC micrographs of Gaeolaelaps furcatus Joharchi & Ueckermann sp. nov., female. 11, idiosoma in dorsal view; 12, idiosoma in ventral view; 13, sternal & genital shields; 14, details of peritrematal shield; 15, subcapitulum, hypostomal groove; 16, distal portion of palp, with a focus on apotele; 17, chelicera; 18, pretarsus III, pretarsal paradactyli (p.p), pulvillar lobe (p.l).

FIGURES 19–22. Gaeolaelaps furcatus Joharchi & Ueckermann sp. nov., female. 19, leg I (trochanter-tibia); 20, leg II; 21, leg III, enlarged section not to scale; 22, leg IV, enlarged section not to scale. Abbreviations: pretarsal paradactyli (p.p), pulvillar lobe (p.l).