Tarsonemus mondouriensis Karmakar and Ganguly

Mondal, Priyankar, Ganguly, Moumi, Karmakar, Krishna & de Moraes, Gilberto J., 2022, Two new species of Tarsonemus (Acari: Tarsonemidae) from the Indo-Gangetic plains of West Bengal, India, with brief notes on their bioecology, Journal of Natural History 55 (41 - 42), pp. 2569-2588 : 2578-2584

Tarsonemus mondouriensis Karmakar and Ganguly sp. nov.

( Figures 13–24, 30–33)

Diagnosis

Adult of both sexes. Pharynx fusiform, with thick muscular walls. Sejugal apodeme conspicuous laterally, curved inwards and characteristically indented at junction with prosternal apodeme. Sensory cluster on tibia I complete. Setae pl” present on tarsus II. Setae pv” absent on tarsus III. Female: Anterior small hood-like extension of prodorsal shield covering almost half of gnathosoma; setae sc2 more than twice length of v1; setae c1 nearly half length of c2; setae d, e, f and h weakly barbed; dorsal plates ornamented with faint punctations and margins perpendicularly striate. Apodemes 4 with a submedial node diffusely meet narrow poststernal apodeme; the latter weakly bifurcated anteriorly. Leg I with strongly curved claw, seta d smooth and longer than length of tibiotarsus I; tc” twice length of v’Ti on leg IV, both setae smooth. Male: Gnathosomal capsule with transverse sclerotisation posterior to pharynx; dgs and vgs of equal length. Dorsal setae barbed except sc2 and c2; setae sc1 nearly thrice length of sc2 and slightly more than twice length of v1; c2 almost twice length of d and f. Dorsal plates ornamented with faint punctations. Seta 3b almost twice length of 2a and nearly equal to length of 3a. Coxisternal plates adorned with minute longitudinal striations. Solenidian ω on tarsi I and II similar in length; femorogenu IV more than twice longer than wide basally; distal inner margin of femorogenu IV conspicuously concave; v’Ti slightly longer than two-thirds length of femorogenu IV; claw 1.5 times longer than combined length of tibia and tarsus IV.

Adult female (6 specimens measured).

Gnathosoma: subtriangular, length 36 (34–39), maximum width 33 (30–35). Setae dgs 14 (12–16) and vgs 9 (8–10), both smooth; seta pp indiscernible. Palpi short with 2 small subterminal setae and a pair of dentate structures apically. Pharynx fusiform, muscular, 24 (22–25) long and 9 (8–10) wide at widest level, nearly one-fourth width of gnathosomal capsule. Cheliceral levers with characteristic lateral projections directed posteriorly.

Idiosoma ( Figures 13, 14): length 230 (221–235), maximum width 150 (146–157) at level of c1. Dorsum: Prodorsal shield anteriorly with a small hood-like extension covering one-third of gnathosoma with posterior margin slightly convex. Stigma located on lateral margin of prodorsal shield, closer to bases of v1 than sc1; atria sac-like, often banana shaped. Bothridial seta sc1 globose and spiny, located ventrolaterally almost equidistant from sc 2 and v1. Dorsal plates with faint punctations and margins perpendicularly striate. Length of setae: v1 37 (36–39), sc1 15 (14–17), sc2 77 (75–80), c1 17 (16–19), c2 32 (31–34), d 13 (11–14), e 15 (13–16), f 17 (17–20), h 18 (17–19). All dorsal podosomal setae setiform, pointed; setae d, e, f and h weakly barbed, others smooth. Distances between setae: v1–v1 25 (22–26), sc2–sc2 50 (47–52), v1–sc2 38 (35–39), c1–c1 82 (80–86) c2–c2 112 (108–114), c1–c2 30 (28–33), d–d 40 (37–41), f–f 27 (25–28), e–f 33 (29–33), h–h 50 (48–52). Venter: coxisternal setae 1a 10 (9–11), near middle of apodemes 1 and slightly above level of point of fusion of apodemes 1 and prosternal apodeme; 2a 9 (8–10) mediad apodemes 2; 3a 19 (17–20) near proximal end of apodemes 3; 3b 12 (10–14) located at distal end of apodemes 4; all setae smooth. Seta 1b and 2b absent, only pits visible. Apodemes 1 conspicuous, converging posteriorly to fuse with anterior end of prosternal apodeme. Apodemes 2 conspicuous, narrowed proximally and clearly separated from prosternal apodeme. The latter conspicuous throughout entire length and prominently fused with sejugal apodeme. Sejugal apodeme conspicuous, laterally curved inwards and characteristically indented at junction with prosternal apodeme. Apodemes 3 extending diagonally from anterior end of trochanters III towards base of 3a with proximally truncated ends; apodemes 4 with a medial node, diffusedly meeting poststernal apodeme from which they extend diagonally up to base of seta 3b. Poststernal apodeme straight and conspicuous for most of its length but weakly bifurcate anteriorly. Coxisternal plates smooth; fused coxisternal plate III and IV does not overlap sejugal apodeme. Tegula triangular, 3 (3–5) long and 9 (8–10) wide at level of lower margin of coxa 4. Seta ps slender 10 (8–11), weakly barbed.

Legs ( Figures 15–18): lengths (femur to tarsus): leg I 57 (52–58), leg II 54 (50–56), leg III 58 (54–59), leg IV 43 (42–46). Number of setae (solenidia in parentheses) on femur, genu, tibia and tarsus, respectively: leg I: 4-4-6(2)+8(1), leg II: 3-3-4-7(1), leg III: 1+3-4-5, leg IV: 1+1-1+1. Claw of leg I strongly hooked. Tibiotarsus I with solenidion ω 6 (5–6) clavate; seta pv’ 19 (17– 21) and pv” 11 (9–13); both setae smooth, attenuated; seta pl” 9 (8–11) slender, tapering towards end. Sensory cluster of tibia I complete, solenidia φ1 3 and φ2 4 (3–4), clavate; famulus k 5, inserted at same level as solenidia. Seta d of tibia I 35 (32–37) long, smooth; seta v’ 6 (5–8), slender, attenuated. Genu I with seta l’ 6 (5–7), smooth, attenuated; v” on femur I 10 (8–13), smooth, setiform. Solenidion ω of tarsus II proximal, 4 (3–4) long, stout, clavate; seta pl” thorn-like, 2 (2–3) long, inserted at same level as ω; seta u’ thicker, nearly as long as u”. Seta d of tibia II 24 (22–25), smooth, setiform; seta l’ on femur II smooth tapering towards end; l’ on genu II stiff, slightly barbed. Seta d distad tibia III, smooth, setiform, 10 (9–13) long; pv” absent on tarsus III; both unguinal setae present; u” slender, longer than stiff u’. Femorogenu IV 35 (32–36); tibiotarsus IV 8 (7–9). Lengths of setae of leg IV: v’ F 16 (14–17), v’ G 12 (11–14), v’ Ti 30 (28–33) and tc” 67 (64–69); all setae smooth.

Adult male (4 specimens measured).

Gnathosoma: subtriangular, length 23 (21–24), maximum width 25 (23–26). Setae dgs 10 (8–10) and seta vgs 10 (7–9), both smooth; seta pp indiscernible. Palpi short with 2 small subterminal setae and a pair of dentate structures apically. Pharynx well muscled, fusiform, 16 (15–17) long and 7 (6–7) wide at widest region, nearly one-fourth width of gnathosomal capsule.

Idiosoma ( Figures 19, 20): length 144 (128–137), maximum width 91 (77–84). Dorsum: Prodorsal shield trapezoidal, anterior margin slightly concave. Length of setae: v1 26 (22– 26), v2 13 (19–22), sc1 57 (67–71), sc2 20 (23–26), c1 24 (22–25), c2 29 (22–25), d 15 (20–23), f 14 (12–15). Prodorsal setae setiform, barbed, pointed apically except sc2 which is smooth; all dorsal hysterosomal setae except c2 barbed; setae c1, d and f thick, barbed and blunt ended. Distances between setae: v1–v1 11 (13–16), v2–v2 22 (22–25), v1–v2 16 (13–116), sc1–sc1 34 (32–36), sc2–sc2 48 (38–43), sc1–sc2 6 (5–7) v2–sc2 17 (17–21), c1–c1 76 (66–71), c 2 –c 2 84 (82–87), c1–c2 32 (27–31), d–d 29 (28–32), f–f 24 (21–25). Seta c1 almost equidistant from c2 and d. Dorsal plates ornamented with faint punctations. Venter: coxisternal setae 1a 11 (10– 13) long, posteriad apodemes 1 and slightly below level of point of fusion of apodemes 1 and prosternal apodeme; 2a 8 (7–9) posteriad apodemes 2, on upper half of coxisternal plates II; 3a 18 (16–19), at anterior end of apodemes 3; 3b 16 (15–18), nearly mediad apodemes 4; all setae smooth. Seta 1b and 2b absent, only pits visible. Apodemes 1 conspicuous, converging posteriorly to fuse with anterior end of prosternal apodeme. Apodemes 2 conspicuous, with diffused triangular projections anteriorly, converging posteriorly, barely reaching prosternal apodeme. The latter straight, conspicuous throughout entire length and prominently fused with sejugal apodeme. Sejugal apodeme conspicuous, laterally curved downwards and characteristically indented at junction with prosternal apodeme. Apodemes 3, 4, and poststernal apodeme conspicuous, anteriorly fused with each other by transversal lines, which together make sinuate lobed margin anteriorly. Coxisternal plates adorned with minute striations.

Legs ( Figures 21–24): length (femur to tarsus): leg I 58 (52–60), leg II 53 (50–55), leg III 64 (62–67), leg IV 51 (49–54). Number of setae (solenidia in parentheses) on femur, genu, tibia and tarsus: leg I: 4-4-6(2)-8(1), leg II: 3-3-4-7(1), leg III: 1-3-4-5, leg IV: 1-3-1(1)+3. Claw of leg I strongly hooked. Solenidion ω of tarsus I 7 (7–8), stout, clavate; seta pv’ 9 (8–11) and pv” 11 (10–13); both setae smooth, attenuate; seta pl” 2, spinose and smooth, inserted distad the level of ω. Sensory cluster of tibia I complete, solenidion φ1 4 (3–4) long, clavate; solenidion φ2 3 long, capitate; famulus k 3 (2–3) rod-like, inserted at nearly same level as solenidia. Seta d of tibia I 21 (20–24), smooth; seta v’ 5 (5–8), slender, attenuated. Genu I with seta l’ 5 (5–7) smooth, attenuated; v” 14 (12–15) on femur I slightly serrate, setiform. Solenidion ω of tarsus II proximal, 7 (7–9) clavate; seta pl” 2 (2–3) long, thorn-like, inserted at same level as ω; seta u’ thicker,slightly shorter than u”,both spinose. Seta d of tibia II 10 (9–12), smooth;seta l’ on both femur II and genu II smooth and setiform. Seta d 17 (14–18), slightly barbed, setiform, mediad tibia III; pv” absent on tarsus III; both unguinal setae present; u” slender as long as stiff u’. Seta v’ of trochanter IV 12 (10–13),smooth; femorogenu IV, 42 (38–44) long and 18 (17–20) wide at v’ F level, without flange, posterior inner margin concave and outer margin conspicuously convex. Setae v’ F 14 (12–16), v’ G 22 (20–24), barbed; l” G 26 (24–28) smooth; tibia IV 6 (6–8), solenidion φ 6 (6–7), bacilliform, v’ Ti 34 (32–38), barbed; tarsus IV 3 (3–4), tc” 5, pv” 5 (5–6) and u’ 6 (5–6). Claw well developed, stout, unciform, 14 (12–15) long, 6 (5–7) wide basally.

Differential diagnosis. This new species is most similar to Tarsonemus bilobatus Suski, 1965 and T. ligracis Kaliszewski, 1993 in having minute punctations on dorsal and ventral plates, dorsal setae d, e, f and h barbed, apodemes 2 straight, not fused with prosternal apodeme and sejugal apodeme conspicuously bent inwards and characteristically indented at middle in the case of adult females. Tarsonemus mondouriensis Karmakar and Ganguly sp. nov. females differ from those of T. bilobatus by longer dorsal setae v1 (36–39 vs 29–32) and sc2 (75–80 vs 64); shorter dorsal setae c1 (16–19 vs 25); poststernal apodeme with weak bifurcation anteriorly and weakly fusing with apodemes 4 (poststernal apodeme strongly bifurcated anteriorly, strongly fusing with apodemes 4 in T. bilobatus ); and tegula thrice wider than long (tegula twice wider than long in T. bilobatus ). Females of this new species also differ from those of T. ligracis by seta v1 setiform and smooth (compared to v1 coarse and blunt ended in T. ligracis ); longer dorsal setae v1 (36– 39 vs 12–15), sc2 (75–80 vs 37–40), c2 (31–34 vs 15–18), e (13–16 vs 8–9), f (17–20 vs 10) and h (17–19 vs 9); longer ventral setae 1a (10–11 vs 4–5), 3a (17–20 vs 11–13), 3b (10–14 vs 6–7) and ps (8–11 vs 4–5); prosternal apodeme conspicuously fused with sejugal apodeme (prosternal apodeme diffused and widened past beyond level of apodemes 2 in T. ligracis ); and poststernal apodeme with diffused bifurcation anteriorly (compared to conspicuous but small bifurcation in T. ligracis ). Females of T. mondouriensis sp. nov. also resemble those of T. smithi Ewing, 1939 , T. acerbilis Delfinado, 1976 , T. saccatus Livshits, Mitrofanov and Sharonov, 1979 and. T. stagnalis Livshits, Mitrofanov and Sharonov, 1979 with respect to the characteristic indentation of sejugal apodeme at junction with prosternal apodeme. They differ from T. acerbilis by prosternal apodeme conspicuous throughout (vs prosternal apodeme interrupted between apodemes 1 and 2); and poststernal apodeme weakly bifurcated anteriorly (compared to conspicuous bifurcation in T. acerbilis ). They differ from T. smithi by seta v1 smooth (v1 strongly barbed in T. smithi ); prominently longer dorsal setae; prosternal apodeme straight without any knob (compared to knob-like thickening in 1/3rd of prosternal apodeme in T. smithi ); poststernal apodeme with weak anterior bifurcation (poststernal apodeme not bifurcated but with irregular thickening at anterior end in T. smithi ). Males of this new species also differ from those of T. acerbilis by dorsal seta sc1 almost thrice length of sc2 (sc1 equals length of sc 2 in T. acerbilis ); c1 slightly shorter than c2 (c2 nearly thrice as long as c 1 in T. acerbilis ); apodemes 2 clearly separated from prosternal apodeme (apodemes 2 uniting with prosternal apodeme in T. acerbilis ); and 2a smaller than 1a (1a smaller than 2a in T. acerbilis ). Females of the new species differ from those of T. saccatus by seta sc1 extending nearly half of its length beyond posterior margin of prodorsal shield (vs sc1 extended only one-fourth of its length beyond prodorsal shield in T. saccatus ); and poststernal apodeme strongly developed with diffused anterior bifurcation (vs poststernal apodeme without bifurcation and submedial interruption in T. saccatus ). Females of T. mondouriensis sp. nov. differ from those of T. stagnalis by shorter setae sc1 (75–80 vs 100–106), e (13–16 vs 31– 35), h (17–19 vs 38), 2a (8–10 vs 15–16) and tc” on leg IV (64–69 vs 112–118). The females of this new species may also resemble those of T. annotatus Livshits, Mitrofanov and Sharonov, 1979 but differ by uninterrupted prosternal apodeme (vs interrupted below level of 1a in T. annotatus ); poststernal apodeme weakly bifurcated anteriorly (vs strongly bifurcated in T. annotatus ); v’ and v” smooth on tibia II (vs v’ and v” smooth on leg II in T. annotatus ); pl” slender, smooth, shorter than ω on tarsus II (pl” stiff, slightly longer than ω on tarsus II in T. annotatus ); and v’ on tibia III smooth (weakly barbed in T. annotatus ).

Type material

Holotype female, male ( Acarol.lab/BCKV/35012-13/2020 ) (submitted to NZC, Zoological Survey of India, Kolkata); 3 paratype females and 2 paratype males ( Acarol.lab/BCKV/35014- 18/2020), from leaves and grains of rice, Mondouri (22.9363o N 88.5086o E), State of West Bengal, 1 February 2020, M. Ganguly and K. Karmakar; 6 paratype females and 3 paratype males ( Acarol.lab/BCKV/35018-21/2020 ), from same host, Tepul village (22.8805o N 88.7869o E), State of West Bengal, 1 February 2020, K. Karmakar and P. Mondal.

Etymology

The specific epithet mondouriensis refers to Mondouri Farm of Bidhan Chandra Krishi Viswavidyalaya, where the holotype specimens were collected.

Remarks

Tarsonemus mondouriensis Karmakar and Ganguly sp. nov. was found to be associated with rice grains. Rice grains collected during Kharif (wet) season from the lower Gangetic plains of West Bengal were found to be infested by both Steneotarsonemus spinki and T. mondouriensis . This new species colonises the lemma and palea of ripe rice grains and sometimes fungus-infested discoloured grains. Mostly 2– 3 adults were found inside each infested grain. We are uncertain whether they are phytophagous and feed on the endosperm inside grains, as the present investigation could not confirm the type of association with its hosts, which requires further study on this species.