Bongotarsonemus bicornus, Mondal & Karmakar, 2021

Mondal, Priyankar & Karmakar, Krishna, 2021, A new genus Bongotarsonemus with two new species of tarsonemid (Acari: Heterostigmata) mites discovered from the Himalayan forests of West Bengal, India, Zootaxa 5072 (6), pp. 575-591 : 585-590

Bongotarsonemus bicornus sp. nov.

( Figs. 14–19 ; 28–31 )

Diagnosis. Prodorsal shield of the adult female is distinctive in having setae v1 each set on a prominently raised tubercle which extends posteriorly up to stigmatal opening; a pair of triangular anterior prodorsal horns between bases of setal pair v1; several elevated striae extending anteriorly up to base of horns and posteriorly to level of insertion of sc2. Dorsal setae c1, c2, d and e subequal in length; setae f nearly twice longer than those, located posterolaterad setae e. Ventral setae 3a thrice the length of 3b. Tarsus I with tc’’ as long as tc’ and tarsus III with tc’ nearly one fourth the length of tc’’. Tarsus II with solenidion ω baciliform, twice as long as pl’’.

Adult female (8 specimens measured).

Gnathosoma: subtriangular, well sclerotized, length 29 (26–30), maximum width 25 (25–27). Seta dgs 14 (12– 15), sparsely barbed and vgs 7 (6–8), smooth; seta pp indiscernible. Palpus short with 2 small subterminal setae and two dentate structures apically. Pharynx fusiform, 20 (17–20) long, two third length of gnathosoma and 9 (8–11) wide at widest level, near about one third the width of gnathosomal capsule. Dorsal apodeme short with visible sclerotization of gnathosomal capsule both basally and laterally. Gnathosoma faintly punctate both dorsally and ventrally.

Idiosoma ( Figs.14, 15 ): length 214 (203–219), maximum width 107 (102–119) at the level of c1. Dorsum: Prodorsal shield covering entire gnathosoma with hood shaped extension anteriorly and nearly straight posterior margin. Stigma located on lateral margin of prodorsal shield, slightly closer to bases of sc1 than v1. Bothridial seta sc1 globose and spiny, located ventrolaterally closer to base of sc 2 than to base of v1. Setae v2 vestigial, only pits are visible. Setae v1 set on a prominently raised tubercle which extend posteriorly at least up to stigmatal opening delimiting an anteriorly raised medial section of prodorsum. A pair of anterior prodorsal horns 4 (3–5) long between bases of setal pair v1. Raised section of prodorsal shield with several elevated strial thickenings; extending anteriorly up to base of horns and posteriorly up to level of insertion of sc2. Dorsal plates coarsely punctate and margins perpendicularly striate. Length of setae: v1 28 (25–29), sc1 13 (12–15), sc2 23 (21–26), c1 12 (10–13), c2 13 (12–14), d 13 (11–14), e 11 (9–13), f 22 (19–23), h 9 (7–10). All dorsal setae coarsely barbed; setae sc2, c1, c2, d, e and f blunt ended, others narrowly pointed apically. Distances between setae: v1–v1 17 (16–19), sc2–sc2 55 (50–56), v1–sc2 57 (53–58), c1–c1 51 (48–52) c2–c2 98 (96–103), c1–c2 27 (25–31), d–d 34 (32–37), f–f 21 (19–23), e–f 26 (22–27), h–h 29 (28–31). Venter: coxisternal setae 1a 11 (9–12), near middle of apodemes 1 and at level of point of fusion of apodemes 1 and prosternal apodeme; 2a 14 (8–10) submediad apodemes 2; 3a 21 (7–10) near anterior end of apodemes 3; 3b 7 (5–7) near posterior end of apodemes 4; all setae smooth. Apodemes 1 conspicuous, converging posteriorly to prominently fuse with anterior end of prosternal apodeme forming a ‘Y’ shape.Apodemes 2 long, diffusely meet prosternal apodeme at proximal part. Prosternal apodeme conspicuous only upto level of anterior end of apodemes 2; diffused and widened afterwards to meet with sejugal apodeme. The latter conspicuous, laterally curved and widely separated medially. Apodemes 3 extending diagonally from anterior end of trochanters III to about longitudinal level of insertion of 3a with proximal end diffused and widened; apodemes 4 diffused proximally and medially, inconspicuously meet the anterior region of poststernal apodeme from which it extends diagonally up to base of setae 3b. Poststernal apodeme straight, mostly conspicuous but weakly bifurcate anteriorly. Coxisternal plates coarsely punctate; anterior margin of fused coxisternal plates III and IV convex. Tegula tongue shaped, 12 (11–14) long and 15 (14–16) wide at the level of lower margin of trochanter IV. Seta ps slender 12 (9–13), smooth.

Legs ( Figs. 16–19 ): lengths (base of femur to apex of tarsus): leg I 52 (48–55), leg II 52 (49–53), leg III 62 (59– 66), leg IV 40 (37–43). 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. Tibiotarsus I with solenidion ω 5 (4–6) long, stout and clavate; pv’’ 15 (14-17) slightly longer than pv’ 11 (10-13), both attenuated; tc’’ as long as tc’ 17 (15-18). Sensory cluster of tibia I complete, solenidion φ1 3, clavate; solenidion φ2 3, stout, capitate; famulus k 4 (4–5), inserted slightly proximal to φ1. Seta d of tibia I 48 (46–51) long, serrate, more than twice the length of tibiotarsus I; seta s of tarsus I 3 (2–3) long, stout, spine like. Seta l’ on genu I 12 (11-14), somewhat thickened and barbed; l’ on femur I 14 (12-16), plumose; v’’ 20 (17-22), attenuated and sparsely barbed. Claw of leg I fish-hook shaped 7 (6-8) long. Solenidion ω of tarsus II proximal, 7 (6–8) long, stout, baciliform; seta pl” spine like, 3 long, inserted at the same level with ω; tc’’ 31 (30–34) nearly twice longer than tc’ 14 (13–16), tc’’ smooth, tc’ sparsely barbed. Seta d of tibia II 15(13–17) long, serrate. Setae l’ on both femur and genu II somewhat thickened and sparsely barbed. Both u’ and u’’ present on tarsus II and III; u’ on both tarsus 5 (4–6) long stout, spine like; u’’ setiform. Seta tc’’ 33 (31–36) nearly four times longer than tc’ 8 (8–10), both sparsely barbed.Femorogenu IV 27 (25–29); tibiotarsus IV 11 (9–13). Lengths of setae of leg IV: v’ F 15 (13–17), v’ G 17 (14–19), v’ Ti 24 (21–26) and tc” 39 (36–42); v’ Ti thickened and serrate.

Adult male. Unknown

Larva. Unknown.

Type material. Holotype female (Acarol.lab/ BCKV/30905 /2021) (submitted to NZC, Zoological Survey of India, Kolkata); 9 paratype females (Acarol.lab/ BCKV/30906-9 /2020), from leaves of Arthromeris wallichiana Rock Garden, Darjeeling (27°01’32”N; 88°14’16”E), State of West Bengal, 12/II/2021, coll. P. Mondal & K. Karmakar.

Etymology. The species name bicornus is derived from two Latin words viz. ‘ bi ’ meaning two and ‘ cornu ’ meaning horn like projection referring the pair of sclerotized anterior prodorsal horns characteristic of this species.

Remarks. Bongotarsonemus bicornus sp. nov. females were collected from sporangia on the leaflets of a mountain fern, Arthromeris wallichiana . The colony of mites was found aggregated within the sporangia but surprisingly no males or larvae were recovered from these colonies despite presence of a good number of females. Direct feeding on fern spores was not observed. The host species is sparsely distributed in the Darjeeling and Sikkim hills of India and used by the locals as vegetables especially the fronds, and the rhizomes are used in ethnomedicine. Prior to this the monobasic genus Eotarsonemus De Leon, 1966 and 3 other species of tarsonemid mite, Hemitarsonemus tepidariorum (Warburton, 1904) , H. ganeo Magowski, 2012 and Dendroptus (Hemidendroptus) hellulo Magowski 2011 , were reported from ferns ( Lindquist, 1986; Magowski, 2012).

Figures

FIGURES 14–15. Bongotarsonemus bicornus n. sp., (female). 14. Dorsal surface, 15. Ventral surface.

FIGURES 16–19. Bongotarsonemus bicornus n. sp., (female legs). 16.—leg I, 17.—leg II, 18.—leg III, 19. —leg IV.

FIGURES 20–31. Bongotarsonemus spp., 20–27. Bongotarsonemus unicornus n. sp., 20.—Female dorsal surface, 21.—Female ventral surface, 22.—Female legs III & IV, 23.—Female leg I with claw, 24.—Female legs I & II, 25.—Male dorsal surface, 26.—Male ventral surface, 27.—Male leg IV with claws and solinidia.