Parisotoma sexsetosa Potapov, Janion & Deharveng, 2011, sp. nov.

Parisotoma sexsetosa sp. nov.

Figs 1, 7–23.

Material. Holotype female on slide and about 150 paratypes (10 on slide): South Africa: Western Cape: Cape Town: Table Mountain National Park, 10.iii.2009, native forest, in litter, sieving and extraction in Berlese funnel, near Wynberg cave (SAF-141, leg. Louis Deharveng & Anne Bedos); 4 paratypes on slide, ibid (RSA 09-TBM001, leg. Charlene Janion); ibid, about 266 paratypes in alcohol, near Inchuk cave entrance (SAF-144, leg. Louis Deharveng & Anne Bedos).

Holotype and 140 paratypes in Iziko Museum (Cape Town, South Africa). 140 paratypes in MNHN (Paris, France); 140 paratypes in MSPU (Moscow, Russia).

Description. Body length from 0.6 to 1.0 mm. Pale with diffuse greyish pigment on body, eye spot black (Fig. 1). Ant.I with 4–5 sensilla ventro-laterally of which 2 long chaeta-like and 2–3 short, 3 basal microchaetae, 2 dorsal and 1 ventral (Figs 15, 17). Inner sensilla of AO III rather small. Ant.IV with 4 sensilla moderately thickened and several chaeta-like. Subapical microsensillum long curved at apex, subapical organite long, pin-like (Fig. 16).

Two ocelli on each side of head, set together in a single eye spot, large anterior and smaller posterior (Fig. 8). Variation in this character was not found but eye pigmentation sometimes gives an impression of one large ocellus instead of two in dark coloured specimens. PAO wide, ca 1.4 as long as internal crest of Claw III. Labral formula 4/ 554, apical folds sharp, as in P. notabilis. Maxillary outer lobe with 4 sublobal hairs and trifurcate apical palp. Labial palp normal for family with 5 papillae (A–E) and full set of guards (16, including e7), lateral process as for family. Labium with 4 basomedian, 5 basolateral, and 4 proximal chaetae. Number of postlabial chaetae variable, from 4+4 to 8+8, including 4+4 large chaetae (always present) and usually several smaller ones between them. Asymmetrical variants 4+5, 4+6 or 5+6 common (Figs 19–21). Inner mouthparts as usual for the genus. Lamella 1 longer than capitulum with apex fan-shaped expanded, with marginal ciliation and one irregular row of long denticles on inner side. Lamella 6 with marginal ciliation and many irregular rows of denticles (Fig. 18).

Lower subcoxa of leg I with one outer chaeta (Fig. 9). Tibiotarsi of all legs with only 7 chaetae in apical whorl. Claw without clear internal teeth, with two minute lateral teeth (Fig. 22). Empodial appendage with broad lamella. Ventral tube with 2+2 lateral, 3–4+3–4 anterior, and 3–6 posterior chaetae (Fig. 14). Retinaculum with 4+4 teeth and 4(5) chaetae. Furcal subcoxa with 27–31 chaetae. Manubrial thickening simple. Anterior side of manubrium with numerous chaetae of which 2+2 shorter medial ones in its apical part (Fig. 13). Dens with numerous chaetae on anterior side and 6 chaetae on posterior side (2 basal, 2 median and 2 lateral) (Figs 11, 12). Mucro with 3 teeth.

Ordinary chaetae thickened (varies slightly between individuals), as usual for the genus (Fig. 10, 23). Axial chaetotaxy for Th.II, III normally with 12+12, 10+10 chaetae, respectively. Macrochaetae differentiated, ciliate, on last abdominal segments with more than 15 cilia, on Abd.V longer than length of tergite (as 1: 1.1–1.3). Sensilla thin, well different from common chaetae, sensillary chaetotaxy on Th.II–Abd. V as: 2al+4accp, 1al+4accp / 4 accp, 4 accp, 4 accp, 1 am+5 accp, 2 am+5 accp. Comparing with full set of sensilla, 2 of them (accp4 and accp5) are missing on each side of segment from Th.II to Abd.III, and 1 sensillum (accp4) is missing on Abd.IV. Microsensilla (ms) 1,1/1,0,1 on Th.II–Abd.III. Microsensillum of Abd.III large, as long as sensillum (Fig. 10). Following the nomenclature of Potapov (1989) number of common chaetae in p-row between sensilla and microsensilla: 2s1s1s3s (Abd.I), 2–3s1s1s3–4s (Abd.II), 2–3s1s1s2–3ms1s (Abd.III), 1s1s1s2(s)1s (Abd.IV) (Figs 7, 23). Males present.

Distribution. Table Mountain National Park, Western Cape, South Africa.

Remarks. The species is well defined due to reduced sensillar chaetotaxy, six posterior chaetae on dens (shared with P. obscurocellata sp. nov.), 4–8 chaetae on each side in postlabial group on head, and enlarged microsensilla on Abd.III. As a rule, the species is well recognized superficially by two dark ocelli set together in a single eye spot of slightly variable size and shape.

Name derivation. Reflects the low number (6) of posterior chaetae on dens.