Bagnallella tenella (Reuter, 1895) Potapov & Deharveng & Janion-Scheepers, 2021

Potapov, Mikhail, Deharveng, Louis & Janion-Scheepers, Charlene, 2021, Taxonomy of the Proisotoma complex. VI. Rediscovery of the genus Bagnallella Salmon, 1951 and epitoky in Bagnallella davidi (Barra, 2001), comb. nov. from South Africa, ZooKeys 1072, pp. 185-204 : 185

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Bagnallella tenella (Reuter, 1895)

comb. nov.

Bagnallella tenella (Reuter, 1895) comb. nov.

Figures 5-8 View Figures 5–8

Isotoma tenella Reuter, 1895

Proisotoma tenella (Reuter, 1895)

Proisotoma simplex Folsom, 1937

Proisotoma alba Yosii, 1939

Material examined.

South Africa, Western Cape, Haarwegskloof, Swellendam , 34.3425°S, 20.3167°E, 18.vii.2017, litter trap (R17) with Dicerothamnus rhinocerotis litter, O. Cowan leg. GoogleMaps ; Haarwegskloof, Swellendam , 34.3444°S, 20.3225°E, 18.vii.2017, litter trap (A17) with Medicago sativa litter, O. Cowan leg. GoogleMaps ; Eastern Cape, Baviaanskloof , 33.7311°S, 23.9655°E, 24.iv.2013, BAV_F_49, A. Liu leg. GoogleMaps ; Free State Province, Bankfontein Farm , 30.0567°S, 24.8942°E, 24.iv.2019, Berlese-Tullgren, tree leaf litter, H. Badenhorst leg. GoogleMaps

Cuba, Cienfuegos Province, 1984, J. Banasco-Almenteros leg.

Indonesia, Lombok Island , vic. Toko Nusa Sari, marine beech, 8.7411° S, 116.0011° E, 4.IV.2017, V. Makarov leg. GoogleMaps

Brazil, Espirito Santo, Domingos Martins, Arace , 4.VII.2000, M. Culik leg.


Maxillary palp simple. Four prelabral chaetae. Dens slender, with ca 20-30 anterior chaetae. Mucro bidentate. Anterior side of manubrium with 3+3 chaetae. 33/22235 s and 11/111 ms on body. No ventral chaetae on Th.III.


Colour grey of different intensity. Cuticle outwardly smooth. 8+8 ocelli, G and H smaller. PAO (Fig. 6 View Figures 5–8 ) about half as long as width of Ant.I and 0.8-0.9 as long as Claw 3. Maxillary outer lobe with four sublobal hairs and simple maxillary palp. Labral formula as 4/554. Labium without guards e7, with three proximal and four basomedian chaetae. Ventral side of head with 4-5+4-5 postlabial chaetae. With several additional chaetae on Ant.I. Ant.I with three basal micro s-chaetae (bms), one dorsal large, Ant.II with three bms, Ant. III without bms. Thorax without ventral axial chaetae. Macrochaetae rather long, differentiated (11/3334), medial ones on Abd.V about as long as tergal midline. S-chaetae on tergites slightly shorter than ordinary chaetae. S-formula as 33/22235 (s), 11/111 (ms) (Figs 5 View Figures 5–8 , 8 View Figures 5–8 ). S-chaetae subequal, on Abd.I-III in mid-tergal position. Micro s-chaetae on Abd.I-II in front of lateral s-chaetae, on Abd.III between medial and lateral s-chaetae (Fig. 8 View Figures 5–8 ). Tibiotarsal tenent chaetae (1,1,1) often present, weakly clavate (see Discussion). Retinaculum with 4+4 teeth and 1-2 chaetae. Furca long. Anterior side of manubrium with 3+3 chaetae arranged in two lines (Fig. 7 View Figures 5–8 ). Dens with more than 20 anterior chaetae, posterior side of dens with crenulation and 7-10 chaetae (Fig. 7 View Figures 5–8 ). Mucro bidentate. Ratio of manubrium: dens: mucro = 7-8: 9: 1.


The species belongs to the genus Bagnallella by having two last abdominal segments separated and three and five s-chaetae on Abd. IV and V. It shares 3+3 anterior chaetae on manubrium with B. biseta , B. koepckei , and B. paronai from South America from which it differs by fewer chaetae on dens.

Number of posterior chaetae on dens, clavate tibiotarsal chaetae, and chaetae on retinaculum vary. We treat all this variation within one species, but further study is needed. The independence of Proisotoma nigromaculosa (Hawaiian Islands) is doubtful.

Although we have no material from Europe, Stach’s (1947) concept of P. tenella based on the specimens from Poland is accepted by us (for details see Potapov 2001; Fjellberg 2007). Our tropical material fits Stach’s (1947) descriptions.

Distribution and ecology.

Widely distributed cosmopolitan species. Common in tropics. In higher latitudes only in protected soils.

Description of Bagnallella davidi and its forms in South Africa












Bagnallella tenella (Reuter, 1895)

Potapov, Mikhail, Deharveng, Louis & Janion-Scheepers, Charlene 2021

Isotoma tenella

Potapov & Deharveng & Janion-Scheepers 2021

Proisotoma tenella

Potapov & Deharveng & Janion-Scheepers 2021

Proisotoma simplex

Potapov & Deharveng & Janion-Scheepers 2021

Proisotoma alba

Potapov & Deharveng & Janion-Scheepers 2021