Papillacarus (Vepracarus) acaciensis, Arun & Ramani, 2020

Arun, A. & Ramani, N., 2020, Two remarkable new species of oribatid mites (Acari: Oribatida) from Acacia litter of Kerala, India, Zootaxa 4877 (3), pp. 539-558 : 542-548

Papillacarus (Vepracarus) acaciensis sp. nov.

( Figs. 3–12 )

Diagnosis. Body size 376–400 × 148–171. Rostrum rounded. Entire dorsal surface covered with tubercles. Prodorsal, notogastral and neotrichal setae branched and tree-shaped. Sensillus pectinate, with 18 branches. Epimeral setal formula: 7-4-3-3. Genital setae g 6, g 7, g 8, g 10 setiform, remaining pairs arboriform. Ano-adanal plates incompletely separated. Anal and adanal setae branched.

Measurements. Body length 378 (holotype), 376–400 (10 paratypes); body width 166 (holotype), 148–171 (10 paratypes).

Integument. Body colour golden brown. Surface of prodorsum and notogaster with thickly punctate tubercles, subcapitulum and epimeral region ornamented with weakly developed tubercles showing thick punctations.

Prodorsum ( Fig. 3 ). Prodorsum broadly conical, rostrum rounded. All prodorsal setae branched and of varying length. Rostral seta the longest (ro, 52). Lamellar seta (le, 41), interlamellar seta (in, 45), anterior exobothridial seta (exa, 44), posterior exobothridial seta (exp, 42). Sensillus (ss, 55) pectinate, with 18 long branches on one side, and six small barbs on the opposite side, the branches more or less of equal length at middle, but progressively decreasing towards the anterior and posterior ends. Prodorsal surface ornamented with tubercles. A feebly developed postbothridial transverse band (S b) present at the interlamellar area. Weakly developed polygonal sculptures bearing fine punctation present, posterior to S b. Lateral prodorsal margin bears distinct tooth like projection, one on either side, above the level of seta exa.

Notogaster ( Figs. 3–4 , 5, 8 ). Anterior notogastral margin straight. Entire notogastral surface covered with densely punctate tubercles, except the area lying just below the dorsosejugal suture where thick punctations present. Thick punctations are also seen scattered on the notogaster. Sixteen pairs of primary notogastral setae and more than 18 pairs of additional neotrichal setae present, all branched with 5–9 branches and show variation in length as: c 1, d 1, e 1, p 2, h 2 (26–32); c 2, d 2, f 1, h 1, p 1, c 3, d 3, e 2, f 2, h 3, p 3 (36–46). Neotrichal setae arise after f setae. Lyrifissures ia, im, ih and ip visible as figured.

Gnathosoma ( Figs. 4 , 6–7 ). Subcapitulum longer than wide (100×67). Less prominent tubercles with fine punctations present on mentum. Five pairs of subcapitular setae detected, a (27) setiform, smooth and pointed apically; h barbed (19), m 1, m 2, m 3 (18–20) setiform, and barbed. Three pairs of smooth adoral setae present: or 1 (14) wider proximally, tapering apically and with a blunt tip; or 2 long (15) and or 3 small (11), both with blunt tip. Rutellum with 3–6 blunt dendrites. Palpal (39) surface punctated, palpal setal formula 0–1–0–1–10 (+1 ω), solenidion blunt distally. Chelicera (117) with 3–5 teeth, seta cha (4) short, thorn-like, seta chb (34) long, setiform and smooth.

Epimeral region ( Fig. 4 ). Epimeral plates distinct, surface with punctations. Epimeres I and II carry neotrichal setae, all branched, epimeral setal formula 7-4-3-3. Setae 1a-e, 2a, 3a, 4a-c (7–15) shorter and thinner than 1f-g, 2b-d, 3b-c (21–34).

Anogenital region ( Fig. 4 ). Transverse suture divides each genital plate into smaller anterior and larger posterior sections. Genital setae g 6, g 7, g 8, g 10 setiform and smooth (17–19), other setae branched (11–14). Anal and adanal plates separated along the antero-median region while the postero-median regions fused. Two pairs of anal (an 1, an 2, 25–21) and four pairs of adanal setae (ad 1-4, 30–42) present, all possess several long branches. Adanal setae longer than the anal setae. Both the genital and ano-adanal plates bear punctation. Lyrifissure iad distinct.

Legs ( Figs. 9–12 ). All legs bearing a single claw each, and claws with a small basoventral tooth. Segments of all legs finely punctate. Trochanters I & II devoid of setae while III & IV with two setae each. Femur I with a posteroventral tooth and an antero-ventral flange like expansion, femora III and IV each with antero-ventral tooth. On genu I, two solenidia (σ 1, σ 2) present, the latter longer than the former and tapering distally. Genua II, III and IV with a single solenidion each. A single solenidion (φ) present on tibia of all legs, except that of leg IV. Tarsus I bears two solenidia (ω 1, ω 2) while tarsus II possesses a single solenidion. The remaining tarsi devoid of solenidia. Famulus (ɛ) of tarsus I short and blunt and placed distal to the stout solenidion ω 1, ω 2 of tarsus I long and tapering. Solenidion on tibial segment (φ) of legs III and IV thick with blunt tip while those of other legs thin and tapering. Chaetotaxy of legs I–IV: 0-5-2(2)-3(1)-17(2); 0-5-2(1)-2(1)-12(1); 2-4-2(1)-1(1)-11(0); 2-3-2(1)-3(0)-11(0) (see Table 1 )

Materials examined. Holotype and 10 paratypes: Collected from densely accumulated litter samples of A. auriculiformis¸ Calicut University Campus (11° 8’ 6.468’’ N 75° 53’ 18.5028’’ E), Malappuram (Dt.), Kerala, India, Coll. Arun, A. on 13.iv.2019.

Type deposition. The holotype and five paratypes are deposited in the Zoological survey of India , Western Ghat Regional Centre , Kozhikode , Kerala, India ; and four paratypes are in the Acarology Collections , Division of Acarology , Department of Zoology, University of Calicut , Malappuram, Kerala, India .

Etymology. The species name “ acaciensis ” is derived from the litter of A. auriculiformis , which formed the natural habitat of the species.

Ecology. All the life stages of Papillacarus (V.) acaciensis sp. nov. such as the larvae, the three nymphal stages and adults were recovered from the decomposing litter of A. auriculiformis . Acacia litter was recognized as the naturally preferred diet of the species, supporting its reproduction and subsequent completion of life history as evidenced through the detection of varied number of food boli in the gut of field collected life stages of the species (personal observation).

Remarks. The specimens of Papillacarus (V.) acaciensis sp. nov. when compared with the other known congeners, were found to show most resemblance to the North Indian species, P. (V.) cornutus ( Sarkar & Subías, 1984) , in the nature of prodorsal and notogastral setae, presence of a tooth on the lateral prodorsal margin, above the insertion of seta exa and the possession of tubercles on prodorsum and notogaster. However, the new species keeps its identity separate from the above species in the following respects (1) incompletely separated nature of anal and adanal plates (in P. (V.) cornutus , anal and adanal plates are completely separated); (2) elongated nature of posteriormost pairs of the notogastral setae (short in P. (V.) cornutus ); (3) presence of feebly developed polygonal sculptures beneath prodorsal band (absent in P. (V.) cornutus ); (4) differences in the length of barbs on ss (distal and basal barbs of ss shorter than the medial barbs in the new species while in P. (V.) cornutus , distal barbs are longer than the basal ones); (5) genital setae g 6, g 7, g 8, g 10 setiform and smooth, and other setae branched (in P. (V.) cornutus all genital setae barbed).

The new species P. (V.) acaciensis shows resemblance to another described species, P. (V.) incompletus ( Mahunka, 1985) described from India in the branched nature of prodorsal and notogastral setae and incomplete separation of ano-adanal plates. However, the new species is distinct from the above species in having: (1) an ornamentation of dorsal surface with tubercles (papilli in P. (V.) incompletus ); (2) seta exp shorter than ss (exp longer than ss in P. (V.) incompletus ) and (3) epimeral setal formula of 7-4-3-3 (9-4- 3-4 in P. (V.) incompletus ).

Figures

FIGURE 3. Papillacarus (Vepracarus) acaciensis sp. nov., adult dorsal view. Scale bar 50 µm.

FIGURE 4. Papillacarus (Vepracarus) acaciensis sp. nov., adult ventral view. Scale bar 50 µm.

FIGURES 5–8. Papillacarus (Vepracarus) acaciensis sp. nov., adult; 5. notogastral seta; 6. subcapitulum, ventral view; 7. chelicera, left; 8. notogastral tubercles. Scale bar 30 µm.

FIGURES 9–10. Papillacarus (Vepracarus) acaciensis sp. nov., adult legs showing segments femur to tarsus, antiaxial view. 9. leg I, left; 10. leg II, left. Scale bar 30 µm.

FIGURES 11–12. Papillacarus (Vepracarus) acaciensis sp. nov., adult; legs showing segments trochanter to tarsus, antiaxial view. 11. leg III, left; 12. leg IV, left. Scale bar 30 µm.