Metatarsonemus shirishi Karmakar & Mondal, 2021

Mondal, Priyankar & Karmakar, Krishna, 2021, First record of Metatarsonemus (Acari: Tarsonemidae) from India with description of two new species, Zootaxa 4942 (2), pp. 229-251 : 238-250

Metatarsonemus shirishi Karmakar & Mondal sp. nov.

( Figs.13–29 ; 35–39 )

Diagnosis. Adult of both sexes: Sensory cluster on tibia I incomplete, missing ϕ1. Setae pl” absent on tarsus II. Female: setae v1 shorter than setae sc2; setae c1 slightly shorter than setae c2. Ventral surface of podosoma with fissures in two regions: a short triangular fissure laterad bases of seta 1a and 2a; a small subcircular unpaired fissure at posterior end of poststernal apodeme and a pair of angulate fissures at base of seta 3b; tegula short, wider than long. Male: setae v1 slightly shorter than setae sc2; setae c2 longer than c1 and d. Apodeme 5 present. Solenidion ω larger and more swollen on tarsus II than on tarsus I, approximately two times longer than basal width of tarsus II; leg IV with tibial tactile setae not longer than femorogenu.

Adult female (8 specimens measured).

Gnathosoma: subcircular, length 24 (22–26), maximum width 22 (20–22). Seta dgs 10 (9–10) and vgs 6 (5–6), both smooth; seta pp absent. Palpus short with 2 small subterminal setae and few dentate structures apically. Pharynx fusiform, 16 (14–16) long and 7 (6–7) wide at widest level, near about one third width of gnathosomal capsule.

Idiosoma ( Figs.13 , 14 ): length 185 (182–191), maximum width 111 (108–119) at level of c1. Dorsum: Prodorsal shield covering almost entire gnathosoma with a convex anterior and posterior margin. Stigma located on lateral margin of prodorsal shield, slightly closer to bases of v1 than sc1. Bothridial seta sc1 globose and spiny, located ventrolaterally, closer to base of sc2 than v1. Dorsal plates with margins perpendicularly striate. Length of setae: v1 19 (18–21), sc1 12 (12–13), sc2 33 (30–34), c1 23 (20–24), c2 18 (16–19), d 16 (15–17), e 11 (10–13), f 19 (17–20), h 13 (12–15). All setae setiform, seta sc2 thick and smooth, others serrated. Distances between setae: v1–v1 26 (24–27), sc2–sc2 50 (47–52), v1–sc2 23 (21–25), c1–c1 43 (41–48) c2–c2 75 (72–77), c1–c2 32 (30–34), d–d 35 (32–36), f–f 21 (18–21), e–f 12 (10–13), h–h 24 (22–26). Venter: coxisternal setae 1a 6 (6–7), near middle of apodemes 1 and just behind the point of fusion of apodemes 1 and prosternal apodeme; 2a 10 (10–11), close to mediad apodemes 2; 3a 18 (17–20), near anterior end of apodemes 3; 3b 10 (8–10), near posterior end of apodemes 4; all setae smooth; setae 1b and 2b vestigial, only pits visible. Apodemes 1 conspicuous with angular projections at base of gnathosoma, converging posteriorly with a medial bulge to faintly fuse with anterior end of prosternal apodeme.Apodemes 2 short with a medial node, not fused with prosternal apodeme. The latter diffused before meeting apodemes 1 but conspicuous beyond level of 1a, continuous with a median node up to level of proximal ends of apodemes 2, diffused and widened further from this point, extended up to sejugal apodeme. The latter convex, conspicuous throughout. Apodemes 3 extending diagonally from anterior end of trochanter III to about longitudinal level of insertion of 3a with proximal end foot like; apodemes 4 conspicuously united mediad poststernal apodeme from which it extends diagonally up to base of seta 3b. Poststernal apodeme conspicuous with two nodes, one anterior and one posterior to point of fusion with apodemes 4. Coxisternal plates with a set of fissures: a pair of triangular fissures, 5 (4–5) long, laterad bases of 1a and 2a; an unpaired subcircular fissure, 1 long, at posterior end of poststernal apodeme; and a pair of angulate fissures at base of seta 3b. All coxisternal plates smooth. Tegula nose shaped 3 (2–3) long and 14 (12–15) wide at level of lower margin of coxa IV; posterior margin rounded. A pair of ridges 6 long flanking tegula from both sides. Seta ps slender 7 (7–8), serrate.

Legs ( Figs.15–18 ): lengths (femur to tarsus): leg I 41 (39–46), leg II 38 (36–41), leg III 41 (38–43), leg IV 26 (25–30). Number of setae (solenidia in parentheses) on femur, genu, tibia and tarsus, respectively: leg I: 4-4- 6(1)+8(1), leg II: 3-3-4-5(1), leg III: 1+3-4-5, leg IV: 1+1-1+1. Solenidion ω of tibiotarsus I 3 long, stout and capitate. Sensory cluster of tibia I incomplete, solenidion φ1 missing; solenidion φ2 3, stout, clavate; famulus k 4 (3–4), inserted approximately at same level. Seta d of tibia I 20 (18–22) long, smooth. Solenidion ω of tarsus II proximal, 4 (4–5) long, stout, capitate; seta pl” absent. Seta d of femur II 6 (6–7) long, serrate; seta d of tibia II 8 (8-10) long, smooth. Femur I and II with ventral flanges. Femorogenu IV 18 (16–19); tibiotarsus IV 8 (7–10). Length of setae of leg IV: v’F 10 (9–10), v’G 16 (15–17), v’Ti 22 (21–24) and tc” 31 (28–34); all setae smooth.

Adult male (4 specimens measured).

Gnathosoma: subtriangular, length 20 (22–26), maximum width 19 (22–25). Setae dgs 9 (9–10) and seta vgs 7 (6–7), both smooth; seta pp absent. Palpus short with 2 small subterminal setae and few dentate structures apically. Pharynx fusiform, 14 (14–18) long and 6 (6–7) wide at widest region, almost equal to one third width of gnathosomal capsule.

Idiosoma ( Figs.19 , 20 ): length 128 (125–137), maximum width 70 (68–73). Dorsum: Prodorsal shield trapezoidal. Length of setae: v1 18 (17–19), v2 15 (14–17), sc1 26 (25–27), sc2 21 (20–22), c1 16 (15–17), c2 21 (20–24), d 12 (10–12), f 13 (11–14). All setae setiform, thickened and serrate. Distances between setae: v1–v1 10 (8–10), v2–v2 19 (18–21), v1–v2 8 (8–10), sc1–sc1 26 (25–29), sc2–sc2 37 (34–40), sc1–sc2 8 (7–9) v2–sc2 16 (14–17), c1–c1 54 (52–56), c2–c2 63 (59–65), c1–c2 33 (30–34), d–d 29 (27–32), f–f 18 (16–20). Seta c1 closer to d than c2. Venter: coxisternal setae 1a 6 (6–7) long, located at longitudinal level mediad apodemes 1 and behind level of point of fusion of apodemes 1 and prosternal apodeme; 2a 9 (8–10) located below the anterior end of apodemes 2; 3a 14 (13–15), near anterior end of apodemes 3; 3b 12 (11–13), near anterior end of distal half of apodemes 4; all setae smooth; setae 1b and 2b vestigial, only pits visible. Apodemes 1 conspicuous, converging posteriorly to fuse with prosternal apodeme. The latter interrupted in region where it would meet with apodeme 2. Sejugal apodeme conspicuous, almost straight and uninterrupted throughout. Apodemes 3, 4, and poststernal apodeme conspicuous, connected to each other anteriorly by diffused convex lines. Apodeme 5 split conspicuously at the level posteriad setae 3b and extend posteriorly to distal end of coxisternal plates 4. Coxisternal plates 2 with tiny punctations at posterior half.

Legs ( Figs. 21–24 ): length (femur to tarsus): leg I 45 (47–53), leg II 37 (43–50), leg III 37 (46–53), leg IV 54 (52–59). Number of setae (solenidia in parentheses) on femur, genu, tibia and tarsus: leg I: 4-4-6(1)-9(1), leg II: 3- 3-4-5(1), leg III: 1-3-4-5, leg IV: 1-3-1(1)-3 Solenidion ω of tarsus I 4 (4–5), stout, clavate. Sensory cluster of tibia I incomplete, solenidion φ1 absent; solenidion φ2 2 clavate; famulus k 3 (2–3) rod like, inserted in transverse line with φ 2. Seta d of tibia I 12 (12–14), serrate. Solenidion ω of tarsus II proximal, 10 (9–12) long, stout, capitate, always bent posteriorly. Seta d of tibia II 9 (9–11), smooth. Seta v’ of trochanter IV 10 (9–11), smooth; femorogenu IV, 34 (32–39) long and 14 (13–17) wide at v’F level, without flange, posterior margin convex and anterior margin concave. Setae v’F 7 (6–18), smooth; v’G 20 (18–21), serrate; l’G 14 (14–16) smooth; tibia IV 17 (15–19), solenidion φ 4 (3–5), bacilliform, v’Ti 32 (30–35), serrate; tarsus IV 4 (4–5), tc” 4, pv” 3 and u’ 4. Claw well developed, stout, unciform, 14 (12–15) long, 8 (6–9) wide basally.

Larva (3 specimens measured)

( Figs. 25– 29 ; 39 ),

Gnathosoma. Slightly longer than wide, length 23 (21–23), width 21 (19–22). Pharynx length 11 (8–11), width 6 (5–7). Setae dgs 10 (8–10) and vgs 4 (3–4), smooth.

Idiosoma . Length 156 (145–159), width 79 (73–82). Prodorsal shield smooth, surrounded by striated cuticle. Setae v1 16 (13–17), sc1 13 (10–14), sc2 31 (28–33) and v2 vestigial, all setae setiform and smooth. Distance between setae v1–v1 10 (9–12), v2–v2 9 (7–9), sc1–sc1 31 (30–34), sc2–sc2 28 (28–32), v1–sc2 32 (31–37). Setae c1 16 (12–16), c2 15 (13–16), d 19 (17–20), e 18 (16–19), f 16 (15–18), h1 19 (17–19), h2 15 (14–18), all setae slightly barbed and setiform. Setae ps1 3 (2–3), ps2 7 (5–7), both fine and smooth. Distance between setae c1–c1 48 (45–50), c2–c2 59 (47–60), c1–c2 19 (17–24), d–d 24 (23–27), e–e 33 (30–35), e-f 10 (8–10), f–f 15 (14–18), h2–h2 23 (22–25). Coxisternal setae smooth, 1a 6 (4–7), 2a 8 (5–8), 3a 12 (12–14), 3b 9 (8–10); 1b and 2b vestigial, only pits visible. Distance between setae 1a–1a 11 (11–14), 2a–2a 22 (21–25), 3a–3a 24 (23–29), 3b–3b 27 (25–31). Longitudinal striae present between coxisternites III.

Legs. Leg lengths (femoral base to tarsal tip): I 32 (24–33), II 31 (25–32), III 26 (23–35). Leg I with rudimentary claws; legs II–III with small claws. Setal counts for legs I–III (femur to tarsus): 4-4-6(1)-7(1), 3-3-4-5(1), 1-3- 4-5. All setae smooth.

Differential diagnosis: This new species is most similar to Metatarsonemus caissara Lofego & Cavalcante, 2019 having an incomplete sensory cluster on tibia I, pl” absent on tarsus II, coxisternal plate 1 with a set of fissures, tegula wider than long and the male with tiny to coarse punctations on coxisternal plates. Females of M. shirishi differ from M. caissara having much longer dorsal seta sc2 (30–34 vs 16–17), c1 (23–24 vs 11), d (15–17 vs 11), f (17–20 vs 11–12) and presence of coxisternal fissure near base of seta 3b which is absent in the latter. They also differ by shape of coxisternal fissures laterad the bases of 1a and 2a (small triangular in M. shirishi vs elongated curve in M. caissara ), shape of tegula (posteriorly nose shaped in M. shirishi vs posteriorly rounded in M. caissara ), ridges flanking the tegula linear and more than 5 long (compared to shorter angular ridges in M. caissara ) length of ventral seta 3a (17–20 in M. shirishi vs 13–14 in M. caissara ), sclerotization of ventral plate below sejugal apodeme (smooth in M. sirishi vs perpendicular striation in M. caissara ). Males of M. shirishi differ from M. caissara by longer prodorsal setae v2 (14–17 vs 8–10), sc1 (25–27 vs 11–12), sc2 (20–22 vs 17–18) and shorter prodorsal seta d (10–12 vs 21–22); presence of apodeme 5 (compared to its absence in M. caissara ), 3a slightly longer than 3b (compared to 3b nearly half the length of 3a in M. caissara ), coxisternal plates 3 and 4 smooth (compared to ornamentation with punctations in M. caissara ), solenidion distinctly longer on tarsus II (9–12 vs 6–7), and texture of seta v’Ti on genu IV (smooth vs serrate), width of femorogenu at the level of v’G nearly half the length of v’G (compared to width of femorogenu at the level of v’G nearly 1.5 times longer than length of v’G in M. caissara ).

Type material: Holotype female, male; 12 paratype females and 5 paratype males, from barks of Albizia lebbeck, Kalyani (22°59’20”N; 88°27’52”E; 9m MSL), State of West Bengal, 21/IX/2020, P. Mondal and K. Karmakar.

Etymology: The specific epithet shirishi derived from the Bengali word Shirish refers to the local name of Albizia lebbeck , the habitat of the holotype.

Figures

FIGURE 13. Metatarsonemus shirishi n.sp., (female). Dorsal surface.

FIGURE 14. Metatarsonemus shirishi n.sp., (female).Ventral surface.

FIGURES 15–18. Legs of Metatarsonemus shirishi n.sp., (female). 15.—leg I, 16.—leg II, 17.—leg III, 18.—leg IV.

FIGURE 19. Metatarsonemus shirishi n.sp., (male). Dorsal surface.

FIGURE 20. Metatarsonemus shirishi n.sp., (male). Ventral surface.

FIGURES 21–24. Legs of Metatarsonemus shirishi n.sp., (male). 21.—leg I, 22.—leg II, 23.—leg III, 24.—leg IV.

FIGURES 25–26. Metatarsonemus shirishi n.sp., (larva). 25.—Dorsal surface, 26. Ventral surface.

FIGURES 27–29. Legs of Metatarsonemus shirishi n.sp., (larva). 27.—leg I, 28.—leg II, 29.—leg III.

FIGURES 35–39. Metatarsonemus shirishi n.sp., 35.—Female dorsal surface, 36—Female ventral surface, 37.—Female ventral surface, 38.—Male ventral surface, 39.—Larva dorsal.