Parisotoma obscurocellata, Potapov, Mikhail, Janion, Charlene & Deharveng, Louis, 2011

Potapov, Mikhail, Janion, Charlene & Deharveng, Louis, 2011, Two new species of Parisotoma (Collembola: Isotomidae) from the Western Cape, South Africa, Zootaxa 2771, pp. 17-24 : 22-24

Parisotoma obscurocellata sp. nov.

Figs 2–4 , 24–31 .

Type material. Holotype female on slide and about 60 paratypes (12 on slide, 48 in alcohol), South Africa, Western Cape, Kleinmond, Betty's Bay. 11.iii.2008, under creeping plants, extraction in Berlese funnels, legs. Louis Deharveng & Anne Bedos. (SAF-063).

Holotype and 20 paratypes kept in Iziko Museum (Cape Town, South Africa). 20 paratypes in MNHN (Paris, France); 20 paratypes in MSPU (Moscow, Russia).

Description. Body length about 0.8 mm. Pale with weak diffuse greyish pigment on corpus, eye spot black ( Fig. 2 ). Ant.I usually with 4 sensilla ventro-laterally (2 long chaeta-like and 2 short), and 3 basal microchaetae (2 dorsal and 1 ventral). Inner sensilla of AO III of normal size. Ant.IV with 4 sensilla moderately thickened and several chaeta-like. Shape of subapical microsensillum long, slightly curved, and subapical organite not seen. At least 5 ocelli and less than 8 ocelli on each side of head, in divided eye spot, 3–4 in anterior larger group and 2–3 in smaller posterior ( Fig. 25 ).

Exact number of ocelli difficult to see like in some other members of the genus, for example P. notabilis . PAO wide, 1.4 to 1.6 as long as internal crest of Claw III. Labral formula 4/554, apical folds as common for the genus. Maxillary outer lobe with 4 sublobal hairs and trifurcate apical palp (two specimens seen having bifurcate palp). Labial palp normal for family with 5 papillae (A–E) and 16 (15) guards (sometimes e7 lost on one side of the head). Labium with 4 basomedian, 5 basolateral, and 4 proximal chaetae. Invariably 3+3 postlabial chaetae ( Fig. 26 ). Inner mouthparts as usual for the genus. Lamella 1 longer than capitulum with apex fan-shaped expanded, with marginal ciliation and one row of long denticles on inner side. Lamella 6 with many weak denticles in irregular rows ( Fig. 30 ).

Lower subcoxa of leg I with one outer chaeta. Tibiotarsi of all legs with only 7 chaetae in apical whorl. Claw with clear internal tooth, lateral teeth uncertain ( Fig. 28 ). Empodial appendage with broad lamella. Ventral tube with 2+2 lateral, 3+3 or 2+3 anterior, and 3 posterior chaetae. Retinaculum with 4+4 teeth and 2–3 chaetae. Furcal subcoxa with 28–33 chaetae. Manubrial thickening simple. Anterior side of manubrium with numerous chaetae of which 2+2 shorter medial ones in its apical part. Dens with numerous chaetae on anterior side and 6 chaetae on posterior side (2 basal, 2 median and 2 lateral) ( Fig. 29 ). Mucro with 3 teeth.

Ordinary chaetae thickened ( Figs 27, 31 ). Axial chaetotaxy for Th.II, III 9–11 +9–11. Macrochaetae differentiated, on Abd.V slightly longer than length of tergite (as 1: 1.1), ciliate on last abdominal segment with up to 9 long cilia. Sensilla thin, well different from common chaetae, sensillar chaetotaxy on Th.II–Abd. V as: 2al+6accp, 1al+6accp / 6 accp, 6 accp, 6 accp, 1 am+6 accp, 2 am + 5 accp. Rarely one of accp-sensilla lost on half of tergite (specimens with 5 accp-sensilla on either Th.II, Abd.I, Abd.II, and Abd.IV seen). Microsensilla (ms) 1,1/1,0,1 on Th.II–Abd.III. Microsensilla of Abd.III normal, about half as long as sensilla ( Fig. 27 ). Following the nomenclature of Potapov (1989), number of common chaetae in p-row between sensilla and microsensilla: 2–3s1s1s1s1s1s (Abd.I), 3s1s1s1s1s1s (Abd.II), 3s1s1s1s1ms0s1s (Abd.III), 1s1s1s1(s)1(s)1s (Abd.IV) ( Fig. 24, 31 ). Males not seen.

Distribution. Betty’s Bay area, Western Cape, South Africa.

Remarks. The species is readily identified by six posterior chaetae on dens and many ocelli arranged in two eye spots. The former character was seen only in two other undescribed species from South Africa and never seen in Northern Asiatic forms. The latter character makes the identification of P. obscurocellata easy even under low magnification. P. greensladeae (1+1 ocelli, Australia) is possibly related with the new species sharing presence of inner tooth on claw, same chaetotaxy of ventral tube and full sensillar set on Abd.IV. The new species differs from P. sexsetosa sp. nov. by full sensillar set (87/66677 vs. 65/44467), fewer postlabial chaetae (3+3 vs. 4+4 or more), number of ocelli (5+5 or more vs. 2+2) and inner tooth on claw (present vs. absent). The very briefly described Isotoma mossopi Womersley, 1934 from South Africa ( Namibia) belongs to Parisotoma , too. It has also a large ocular spot but with only four ocelli according to the original figure. Moreover, the empodial appendage is thinner than in P. obscurocellata .

Generic assignment of the new species is not fully understood. Elongated eye spot with many ocelli (but fewer than 8) places it formally closer to genus Desoria Nicolet. All other characters, especially seven chaetae in apical whorl on tibiotarsi, few chaetae on appendages, sensillar set, maxillary shape indicate genus Parisotoma . The taxonomical value of number of ocelli, a character of adaptive nature, calls for reconsidering the diagnosis of the genus Parisotoma .

Name derivation. The species is named after the number of eyes which are difficult to observe.

Figures

FIGURES 1 – 2. General habitus: 1, P. sexsetosa sp. nov.; 2, P. obscurocellata sp. nov.

FIGURES 3 – 6. Basic sensorial pattern of South African (3 – 4, P. obscurocellata sp. nov.) and North Asiatic (5 – 6, P. l on ga) species; 3, 5, Abd. II; 4, 6, Abd. IV.

FIGURES 24 – 31. P. obscurocellata sp. nov.: 24, sensillar chaetotaxy of the body; 25, ocelli; 26, postlabial and basomedian chaetae; 27, elements of chaetom: macrochaeta (Mac), sensillum (s), microsensillum (ms); 28, claw and empodial appendage; 29, dens, posterior; 30, maxillary head; 31, chaetotaxy of Abd. IV. 1 – 6: accp-sensilla.