Asiolasma angka ( Schwendinger & Gruber, 1992 ), 2019

Martens, Jochen, 2019, An ancient radiation: Ortholasmatine harvestmen in Asia - a new genus, three new species and a revision of the known species (Arachnida, Opiliones, Nemastomatidae), Revue suisse de Zoologie 126 (1), pp. 79-110 : 86-89

Asiolasma angka ( Schwendinger & Gruber, 1992)

comb. nov.

Figs 1 , 16-30

Dendrolasma angka Schwendinger & Gruber, 1992: 57 (description of female).

Cladolasma angka ( Schwendinger & Gruber, 1992) . – Shear, 2010: 17 (transfer). – Schönhofer, 2013: 24 (species listed). – Zhang & Zhang, 2013: 443 (species mentioned). – Zhang, Zhao & Zhang, 2018: 11 (species mentioned).

Material examined: MHNG; female holotype ; THAILAND, Chomthong Province , Doi Inthanon

National Park, 2530 m, 28.11.1990. – 2 juvenile paratypes; same locality; 28.11. 1990, 19.12. 1990 . – MHNG; 1 male, 10 juveniles; same locality, 2530 m; 22.2. 1992 . – MHNG; 1 male, decayed exoskeleton without genitalia, chelicerae and pedipalps; same locality, 2530 m; 22.2. 1992 . – MHNG; 2 juveniles; same locality, 2530; 13.1.1993 . – MHNG, sample THMA-01/15; 1 female; same locality (18°35’05.8’’N, 98°28’52.3’’E), lower montane forest, 2460 m; 26.12. 2001. All collected by P. Schwendinger.

Remark: The species was exhaustively described based on a single female and a number of juveniles. Now also males are available and the diagnosis and description are extended accordingly.

Diagnosis: Small species with distinctly globular body; anterior part of prosoma distinctly prolonged, eye mound and projecting hood markedly elevated, rear part of eye mound and hood forming approximately a right angle with prosoma, eyes situated close to anterior margin of prosoma (la view); opisthosoma dorsally with groups of acute processes or smooth cones on areas II-IV; truncus penis straight, parallel-sided, slightly depress, spicules on glans uniform and symmetrically arranged; male pedipalpal patella with marked proventral brush of small setae.

Description

MALE

Body shape ( Figs 16, 18-19 , 25-26 ): Distinctly globular when seen in la view ( Fig. 26 ).

Body, dorsal side ( Figs 16, 18-19 , 25 ): Eye mound on anterior margin of prosoma distinctly elevated, projecting into distad-directed hood parallel to do body surface, hood slightly curved (la view); hood bearing one central unpaired and five la (slightly irregularly arranged) paired tubercles, sizes on left and right side different, the basic one longest, followed by a very short one, the remainder continuously prolonged towards tip of hood, all tubercles interconnected by small anvil-shaped bridges; one pair of long apophyses projecting from anterior margin of prosoma and closely flanking hood, these apophyses longer than all hood tubercles.

Posterior margin of opisthosoma ( Figs 16, 19 , 26 ), i.e. area V, with a scattered palisade-like row of eight long and tapering tubercles of various lengths, longest in mid-part of row, between the large tubercles few smaller ones interspersed, all of them densely covered by microdenticles, all tubercles interconnected by low anvilshaped microtubercles close to basis.

Lattice of keel cells extremely dense, forming dozens of individual cells surrounded by low anvil-shaped tubercles or keels; single larger cells situated behind Tu oc and on 1st, 2nd and 3rd opisthosomal segment laterally, in addition a row of larger cells on 5th opisthosomal segment. All anvil-shaped tubercles low and recognizable only by their light coloration contrasting with the darker cuticle surface; all large cells blackish in colour, all others light brownish. A pair of enlarged median tubercles consisting of minute thin pointed individual tubercles on scutal area II, two median pairs on area III and three pairs on area IV; all are difficult to see from above. No soil incrustation present.

Body, ventral side: Free tergites visible on ve side, each with low tubercles combined with anvil-shaped tubercles, longer tubercles interspersed; corona analis with strong tubercles as well, less so on free sternites. Front and back side of all Cx of legs with a row of tubercles each, all low and inconspicuous, on Cx I larger in front, each tubercle with low seta. Long rounded tubercles on Cx distally: I 1 retro-la, II 1 retro-la, III -, IV 1 pro-la, 1 retro-la. Massive tubercles on Tr: I 1each pro-la and retro-la, II 1 each prola and retro-la, III 1 each pro-la and retro-la, IV 1 each pro-la and 1 retro-la.

Chelicera ( Fig. 27 ): Basal article in posterior part dorsally slightly enlarged (la view), do side markedly constricted, saddle-shaped (la view), one prominent truncate tubercle with one seta on distal margin of saddle, with few setae laterally and prolaterally, no brush of setae, no obvious glandular tissue. Second article with a strong horn-like apophysis on upper side, pointed, bent downward to prolateral side. Setae of various sizes, largest ones mainly on frontal surface.

Pedipalp ( Fig. 29 ): Tr slender, slightly swollen on do side; three small tubercles on ve side, pointed, with a strong seta each; Fe strong and massive, relatively short, continuously enlarged distally, slightly bent downwards, loosely set with few scattered normal hairs except for two groups of strong setae mediodistally; Pt slightly enlarged and bulge-like ventrally in central part, ventrally and ventro-prolaterally covered with a dense field of short setae, no apparent glandular tissue underneath; Ti cylindrical but slender, with indistinct basal stalk, not curved, with dense cover of clavate hairs concentrated in distal part; Ta more slender than Ti, distinctly stalked, slightly inflated on do side, densely covered with clavate setae all round.

Legs ( Figs 16-19 ): All legs slightly bent ventrally. All articles round, Fe, Pt, Ti and Ta slightly abraded, few microsetae interspersed; several indistinct white-colored noduli on Fe: in male I 3, II 6, III 3, IV 4; in female I 2, II 6, III 3, IV 4.

Genital morphology ( Figs 20-24 ): Penis long, slender, straight, slightly depressed, almost completely parallel-sided all over its length (do/ve and la views), inconspicuously tapering towards glans, base containing pair of short muscles measuring about less than one fifth of total penis length, only slightly broader than rest of penis, deeply split into two parts (do/ve view); penis in la view slenderer than in do/ve view, parallel-sided except for slightly broadened basis, glans slightly tapering towards stylus; glans spindle-shaped and slightly broadened (only in la view), stylus short, with slight helical torsion (la view). Uniformly long, slightly spindle-like spicules and arranged into two chaplet-like groups around the glans: i) six distal spicules in symmetrically annular group on la, do and ve sides, ii) group of four proximal spicules, two of them on la side, two on ve side; no pair of proximal la spicules on distal part of truncus.

FEMALE: General characters similar to those of male; set of tubercles on posterior opisthosomal margin longer than in male ( Fig. 17 ), eight in male, seven in female, in female distances between tubercles larger, with fewer small tubercles interspersed; ve side of female similar to that of male; chelicera ( Fig. 28 ) similar to those of male in proportions and setation, no hook on 2nd article; pedipalp ( Fig. 30 ) as in male, but Fe less bent, less enlarged distally, Pt only slightly enlarged, with few clavate setae ventrally; do lattice pattern similar to that of male.

Measurements: Body length of males: 3.2 (n=2), of females 3.6-3.7 (n=2). Leg II length of male, of female in parentheses: Fe 3.1 (2.9) Pt 0.8 (0.8) Ti 2.4 (2.7) Mt 1.7 (1.6) Ta 1.4 (1.3). Penis length: 1.7.

Variation: Tubercles of prosomal hood often different in length on left and right side, sometimes deformed; small tubercles on base of hood difficult to see and to count; the large apophyses on prosoma front margin projecting from hood, from margin or from either position on left and right side (observed in one specimen).

Relationships: Within Asiolasma the quite isolated position of A. angka is defined by a remarkably globular body shape, by the armament of the do side of the opisthosoma with fine peg-like tubercles (or smooth cones) concentrated in groups ( Fig. 26 ), by the placement of the eyes on the prosoma and by a simple male genital morphology with the smallest number of spicules of all known mainland Asian species.

Distribution ( Fig. 1 ): Asiolasma angka is recorded only from the Doi Inthanon National Park in northern Thailand. According to current knowledge, the species is restricted to this mountain, the highest in Thailand. Despite numerous collecting efforts by litter and soil sieving and by setting pitfall traps by P. Schwendinger at various altitudes and in different seasons between 1990 and 2001, he was able to secure only a few juveniles and three adults, one of them a semi-decayed corpse. Apparently the species is rare and ecologically highly specialized, confined to montane forest in a narrow altitudinal corridor between 2460 m and 2530 m. Juveniles were found in XI, I and II, adults in XI and II, all outside the monsoon season when collecting activity is not hindered by constant and heavy rainfall.

Figures

Fig. 1. Distributional records of ortholasmatine species in East and Southeast Asia. (1) Asiolasma billsheari sp. nov., China, Gansu, Qinling range. (2) A. juergengruberi sp. nov., China, Yunnan, above Lugu Hu. (3) Same species as before, China, north of Lijiang. (4) A. ailaoshan, China, Yunnan, Ailao Shan. (5) A. damingshan, China, Guangxi, Daming Shan. (6) A. schwendingeri sp. nov., Vietnam, Mt Ba Vi. (7) A. angka, Thailand, Doi Inthanon. (8) Dendrolasma parvulum, Japan, Shikoku Island.

Figs 16-19. Asiolasma angka. (16) Body of male in dorsal view. (17) Body of female in dorsal view. (18) Prosoma of male in dorsal view. (19) Opisthosoma of male in dorsal view. Photographs by J. Schmidt.

Figs 20-26. Asiolasma angka, male. (20) Glans penis in lateral view.(21) Same in ventral view. (22) Same in dorsal view. (23) Truncus penis in ventral view. (24) Same in lateral view. (25) Prosoma in dorsal view. (26) Body in lateral view. Scales: 0.2 mm (20-22); 0.3 mm (23-24); 0.8 mm (25-26).

Figs 27-30. Asiolasma angka, male (27, 29), female (28, 30). (27-28) Right chelicera in prolateral view. (29-30) Right pedipalp in prolateral view. Scales: 1.2 mm (27-28); 0.3 mm (29-30).