Hyposternus ceylonicus, Joharchi & Halliday, 2021

Joharchi, Omid & Halliday, Bruce, 2021, A new genus and species of Laelapidae Canestrini from Sri Lanka (Acari: Mesostigmata), Zootaxa 5048 (3), pp. 391-406 : 393-402

Hyposternus ceylonicus sp. nov.

( Figures 1–34 )

Type material: Holotype, female, Sri Lanka, Sabaragamuwa Province, Polgampola , 06°27’ N, 80°12’ E, alt. 42m, 24 January 2019, O. Joharchi, S.G. Ermilov & A.A. Khaustov coll., from forest soil-litter near the Thambadola Ella waterfall . Paratypes, two females, one male and four protonymphs, same data as holotype (in TUMZ) .

Description. Adult female (n=3) ( Figures 1–16 , 18–21 )

Dorsal idiosoma ( Figs 1 , 8, 10 ). Dorsal shield 683–721 long, 376–390 wide, covering entire dorsal idiosoma, oval-shaped, slightly extending onto ventrolateral aspect of idiosoma, faintly reticulated, with 38 pairs of setae, 21 pairs of podonotal setae, z3 absent, 17 pairs of opisthonotal setae, including two pairs of Zx setae, a supernumerary seta Jx present between setae J2-J2-J3-J3, r6 on lateral soft cuticle. All setae slender, smooth and pointed (22–27), much shorter than distance to following setal base, except j1 (32–35) longer and thicker than other podonotal setae; Z5 (60–63) strongly thickened and elongated. Dorsal shield with about 23 pairs of discernible pore-like structures, including 16 poroids (id1, id2, id 4– id6, idm 1– idm6, is1, idx, idl1, idl3, idl4) and seven gland openings (gd1–2, gd4–6, gd8, gd9) ( Figures 1 , 8, 10 ).

Ventral idiosoma ( Figs 1 , 9, 11 ). Tritosternum with paired pilose laciniae (108–115), fused basally (4–6), columnar base 33–35 × 19–21 wide; pre-sternal platelets absent, apparently fused with sternal shield. Sternal shield length 180–189, maximum width 185–190, narrowest between coxae II (126–137), strongly desclerotised, represented by lateral and anterior margins, anterior margin undulating, median posterior margin absent, anterolateral edges fused to endopodal elements to form arms projecting between coxae I–II. Shield remnants capturing gland pores gvb; bearing three pairs of smooth setae (st1 58–60, st2 52–54, st3 47–49) on lateral remnants, setae short, not reaching base of next seta, one pair of reduced lyrifissures adjacent to setae st1, and a pair of reduced poroids between st2 and st3; gland pores gv1 apparently absent ( Figs 1 , 9 , 12 ). Metasternal setae st4 (40–42) and associated poroids located on soft integument. Endopodal plates II/III completely fused to sternal shield, endopodal plates III/IV elongate, narrow and curved. Genital shield tongue-shaped, slightly expanded posteriorly behind setae st5, length 241–244, maximum width 100–107, anterior margin convex, abutting posterior area of sternal shield, posterior margin slightly tapered, surface reticulated with irregular longitudinal lines in anterior region, posteriorly with 6–8 irregular cells behind an inverted-V shaped ridge; bearing a pair of simple setae st5 (28–30) ( Figs 2 , 9, 11 , 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 elongate, somewhat truncate anteriorly, length 152–158, width 76–84, lineate-reticulate in anterior half, post-anal seta (47–51) longer and thicker than para-anal setae (27–31), cribrum consisting of a terminal tuft with 4–5 irregular rows of spicules and a pair of anterior arms extending slightly beyond post-anal seta; anal gland pores (gv3) on anterolateral margin of anal shield ( Figs 2 , 9, 11 , 14 ). Soft opisthogastric cuticle with one pair of small oval metapodal plates and 15 pairs of smooth and very thick setae (Jv1–Jv5, Zv1–Zv 5), Jv1–Jv3, Zv1–Zv2 (20–30), Zv3 (50–53), Jv4–Jv5, Zv4–Zv5 (60–70), including two and three pairs of R and UR setae (20–30), respectively ( Figs 2 , 9, 11 , 14 ). Exopodal platelets between coxae II–III small, subtriangular; parapodal platelets well developed, curved, surrounding coxa IV, gland pores gv2 on median apices of parapodal platelets. Peritreme narrow, maximum width 10–13 µm, extending anteriorly to mid-level of coxa I; peritrematal shield narrow, maximum width 15–17 µm, expanded anteriorly, fused to dorsal shield at level of s1, free from exopodal shields, bearing five pore-like structures, a lyrifissure ip and a gland pore gp at level of coxa II, two lyrifissures ip and a gland pore gp on post-stigmatic section ( Figs 2 , 9, 11 ).

Gnathosoma ( Figs 3–7 , 15–16 ). Epistome subrectangular, anterior margin somewhat truncate, irregularly denticulate ( Fig. 6 ). Hypostomal groove with six transverse rows of denticles, each row with 10–20 small denticles, with smooth anterior and posterior transverse lines, groove greatly wider anteriorly. Hypostome with four pairs of setae, rostral seta (h1) longest, palpcoxal seta thickened, subulate, h1 (39–41)> h3 (28–30)> pc (19–21)> h2 (13–15) ( Figs 3 & 15 ). Corniculi robust, horn-like, extending slightly beyond mid-level of palpfemur. Supralabral process with a thick and undivided apical projection ( Fig. 5 ). Internal malae shorter than corniculi, composed of a pair of smooth median projections, and lateral fimbriate elongate projections, labrum with pilose surface ( Fig. 3 ). Chaetotaxy of palps ( Fig. 4 ): trochanter 2, femur 5, genu 6, tibia 14, tarsus 15, all setae smooth and needle-like except setae d1, d2, al on palpfemur and al1 on palpgenu thickened, al2 on palpgenu paddle-like, palp tarsal claw two-tined ( Fig. 4 ). Fixed and movable digits of chelicera bidentate, reduced dentition, fixed digit with short and relatively thick pilus dentilis, dorsal cheliceral seta conspicuous, prostrate, relatively thick, arthrodial membrane with a rounded flap and normal filaments; cheliceral lyrifissures indistinct ( Figs 7 & 16 ); movable digit 46–49 µm, middle segment including fixed digit 134–138 µm, narrowing and tapered apically.

Legs ( Figs 18–21 ). Legs II (500–521) and III (515–547) short, I (710–730) and IV (713–744) longer. Length of segments: coxa I 80–84, trochanter I 49–53, femur I 135–139, genu I 116–119, tibia I 130–134, tarsus I 200– 205, coxa II 48–51, trochanter II 49–53, femur II 100–103, genu I 75–78, tibia 76–79, tarsus I 142–147, coxa III 48–51, trochanter III 112–115, genu III 71–73, tibia III 70–73, tarsus III 155–161, coxa IV 53–57, trochanter IV 94–97, femur 153–157, genu IV 101–104, tibia IV 113–117, tarsus IV 200–206. Chaetotaxy normal for free-living Laelapidae : Leg I ( Fig. 18 ): coxa 0 0/1, 0/1 0, trochanter 1 1/1, 0/2 1 (ad thickened), femur 2 3/1, 2/3 2 (ad1, pd2, al1 slightly thickened, ad1 longest, 51–54), genu 2 3/2, 3/1 2 (almost all setae elongated, 50–62), tibia 2 3/2, 3/1 2 (almost all setae elongated, 70–87). Leg II ( Fig. 19 ): coxa 0 0/1, 0/1 0, trochanter 1 0/1, 0/2 1 (al thickened), femur 2 3/1, 2/2 1 (ad1 long, 66–70), genu 2 3/1, 2/1 2, tibia 2 2/1, 2/1 2. Leg III ( Fig. 20 ): coxa 0 0/1, 0/1 0, trochanter 1 1/1, 0/2 0, femur 1 2/1, 1/0 1 (ad1 long, 66–71), genu 2 2/1, 2/1 1 (pd2 thickened), tibia: 2 1/1, 2/1 1 (all ventral setae, al1 & pl thickened). Leg IV ( Fig. 21 ): coxa 0 0/1, 0/0 0, trochanter 1 1/1, 0/1 1 (ad slightly thickened), femur 1 2/1, 1/0 1 (ad2 thickened, ad1 macroseta, 97–101), genu 2 2/1, 3/0 1 (av slightly thickened), tibia 2 1/1, 3/1 2 (av thickened). Tarsi II–IV with 18 setae (3 3/2, 3/2 3 + mv, md); most setae on ventral and lateral faces thickened or spine-like ( Figures 19–21 ). Setae ad2–3 and pd2–3 (75–80) slightly longer than others on tarsus IV.All pretarsi with well-developed paired claws, rounded pulvilli and normal ambulacral stalk.

Insemination structures. Not seen, apparently unsclerotised.

Description. Male (n= 1) ( Figures 17 , 22–23 )

Dorsal idiosoma. Dorsal shield 391 long, 205 wide; ornamentation, chaetotaxy, length and form of setae as in female.

Ventral idiosoma ( Figs 17 , 22 ). Sternal, genital, endopodal, ventral and anal shields fused into holoventral shield, 301 long from anterior to posterior margins of shield, 88 wide at level of st2, 94 at st3 level and 94 at broadest point (behind parapodals), anterolateral edges of shield fused to endopodals between coxae I-II; shield reticulate throughout, except smooth median area between setae st 2– 4; with 10 pairs of smooth setae (st 1– 5, Jv 1– Jv3, Zv 1– Zv2) excluding circumanals, post-anal seta (28) longer and thicker than para-anals (21), bearing four pairs of poroids and three pairs of gland pores (gvb, gv2, gv3), iv1 slit-like; cribrum with 3–4 irregular rows of spicules, restricted to region posterior to post-anal seta; metapodal platelets narrow and fused to shield. Soft opisthogastric cuticle with five pairs of short and thick setae, shorter and finer than those of female. Peritremes and peritrematal shields similar to those in female ( Figs 17 , 22 ).

Gnathosoma . Epistome and subcapitulum similar to female. Fixed digit of chelicera with one tooth, a thorn-like pilus dentilis, dorsal seta conspicuous, relatively thick. Movable digit of chelicera with one blunt tooth, spermatodactyl stout and slightly curved dorsally, with truncate tip, free portion of spermatodactyl about as long as movable digit ( Fig. 23 ). Palps similar to those of female.

Legs. Chaetotaxy as in female.

Description. Protonymph (n= 4) ( Figs 24–29 , 30–34 ).

Dorsal idiosoma ( Figs 24 & 30 ). Whitish, oval, with podonotal (252–269 long 214–226 wide) and pygidial (118–130 long 169–175 wide) shields, three pairs of mesonotal scutellae, the largest 33–37 long 9–13 wide, and seven pairs of setae located between podonotal and pygidial shields (s6, J1, J2, Z1, Z2, S2, S3) ( Figs 24–25 , 30–31 ). Podonotal shield weakly reticulated, only distinct in lateral regions, with 11 pairs of simple setae (j1 –6, z2–5, s 4–5) (r2–3, r5 on lateral soft cuticle) and six pairs of pore-like structures, including three pairs of poroids (id4–6), and three pairs of gland pores (gd1–2, gd4). All setae similar in length (23–30) except j1 slightly longer (30–33). Pygidial shield faintly reticulated throughout, with eight pairs of simple setae (J3 –5, Z3–5, S4–5) and pore-like structures, including seven pairs of poroids (idm3–6, idx, idl3–4), and one pair of gland pores (gd8). All setae similar in length (23–30) except Z5 about twice as long (58–61) as other setae ( Figs 24 , 30 ).

Ventral idiosoma ( Figs 25 & 31 ). Tritosternum with paired pilose laciniae (89–95), fused basally (4–6), columnar base 23–26 16–19 wide. Sternal shield indistinct, sternal area with three pairs of smooth setae (st1 31–33, st2 26–28, st3 23–25) and sternal poroids located on soft integument, metasternal setae st4 absent. Anal shield subtriangular, elongate, length 96–99, width 58–61, post-anal seta (36–39) much longer and thicker than para-anal setae (23–26), cribrum consisting of irregular rows of spicules extending slightly beyond post-anal seta; anal gland pores (gv3) on anterolateral margin of anal shield ( Figs 25 & 31 ). Opisthogastric cuticle with five pairs of thorn-shaped setae (st5 11–13, Jv1–2 16–19, Jv5 51–53, Zv2 16–19), five pairs of ivo, a pair of ivp and gv2, and three pairs of small platelets. Peritreme short, located in the region of coxae III/IV ( Fig. 25 ), peritrematal shield lightly sclerotised, reduced to a small fragment between coxae II-III, bearing a pore (gp), and a distinguishable platelet bearing the peritreme. Post-stigmatic section not developed, a lyrifissure ip and a gland pore gp on soft cuticle.

Gnathosoma ( Figs 32–34 ). Epistome subrectangular, anterior margin straight, irregularly denticulate ( Fig. 33 ). Hypostomal groove with six transverse rows of denticles, each row with 13–20 tiny denticles ( Fig. 32 ), with smooth anterior and posterior transverse lines, groove greatly wider anteriorly ( Fig. 32 ). Hypostome with four pairs of setae, h3 (23–25), h1 (25–29), h2 (12–14), palpcoxal pc (14–16) thickened, subulate ( Fig. 32 ). Corniculi robust, horn-like, extending slightly beyond mid-level palpfemur. Supralabral process with a thick and undivided apical projection ( Fig. 33 ). Internal malae shorter than corniculi, composed of a pair of smooth median projections, and lateral fimbriate elongated projections, labrum with pilose surface. Palps and chelicera similar to the adult ( Fig. 34 ).

Legs ( Figs 26 29 ). Legs II (372 382) and III (347 360) short, I (525 535) and IV (460 489) longer. Chaetotaxy: Leg I ( Fig. 26 ): coxa 0 0/1, 0/1 0, trochanter 1 0/1, 0/1 1, femur 2 2/1, 2/1 2 (ad1 longest), genu 1 2/1, 2/1 1, tibia 1 2/1, 2/1 1. Leg II ( Fig. 27 ): coxa 0 0/1, 0/1 0, trochanter 1 0/0, 0/2 1 (al thickened), femur 1 2/1, 2/1 1 (ad1 macroseta), genu 1 2/0, 2/0 1, tibia 1 1/1, 2/1 2. Leg III ( Fig. 28 ): coxa 0 0/1, 0/1 0, trochanter 1 1/1, 0/1 0, femur 1 2/1, 1/0 0 (ad1 macroseta), genu 1 2/0, 2/0 1, tibia: 1 1/1, 2/1 1. Leg IV ( Fig. 29 ): coxa 0 0/1, 0/0 0, trochanter 1 1/1, 0/1 0 (ad thickened), femur 1 2/0, 1/0 0 (ad1, ad2 thickened & ad1 macroseta), genu 1 2/0, 2/0 0, tibia 1 1/1, 2/1 1. Tarsi II-IV with 17 setae (3 3/2, 3/2 3 + md); most setae on ventral and lateral aspects thickened (or spine-like). All pretarsi with well-developed paired claws, rounded pulvilli and normal ambulacral stalk.

Etymology. The species name refers to the name of Sri Lanka (previously known as Ceylon), the country of origin of this species.

Remarks. Hyposternus ceylonicus sp. nov. may be distinguished from other laelapids by the diagnostic features of the genus mentioned above and further emphasized in the Discussion below. In addition, the short setae of the dorsal shield (especially in contrast to elongate Z5), including a single Jx seta and two pairs of Zx setae, and a faintly ornamented dorsal shield may aid in identifying the new species, including from any undescribed related species that may be discovered in the future.

Figures

FIGURES 1–7. Hyposternus ceylonicus gen. nov, sp. nov., female. 1, dorsal idiosoma; 2, ventral idiosoma; 3, subcapitulum; 4, palp; 5, supralabral process; 6, epistome; 7, chelicera.

FIGURES 8–11. DIC micrographs of Hyposternus ceylonicus gen. nov, sp. nov., female. 8, general view dorsally; 9, general view ventrally; 10, idiosoma in dorsal view; 11, idiosoma in ventral view.

FIGURES 12–17. DIC micrographs of Hyposternus ceylonicus gen. nov, sp. nov., female. 12, sternal shield; 13, genital shield; 14, anal shield and portion of opisthogaster; 15, subcapitulum; 16, chelicera (note that the movable digit of left chelicera has been moved from its natural position). Male: 17, idiosoma in ventral view.

FIGURES 18–21. Hyposternus ceylonicus gen. nov, sp. nov., female.18, leg I (trochanter-tibia); 19, leg II; 20, leg III; 21, leg IV.

FIGURES 22–23. Hyposternus ceylonicus gen. nov, sp. nov., male. 22, ventral idiosoma; 23, chelicera.

FIGURES 24–29. Hyposternus ceylonicus gen. nov, sp. nov., protonymph. 24, dorsal idiosoma; 25, ventral idiosoma; 26, leg I (trochanter-tibia); 27, leg II (trochanter-tibia); 28, leg III (trochanter-tibia); 29, leg IV (trochanter-tibia).

FIGURES 30–34. DIC micrographs of Hyposternus ceylonicus gen. nov, sp. nov., protonymph. 30, idiosoma in dorsal view; 31, idiosoma in ventral view; 32, subcapitulum; 33, supralabral process & epistome; 34, chelicera.