Strenzketoma buddenbrocki (Strenzke) Potapov & Babenko & Fjellberg, 2006

Potapov, Mikhail, Babenko, Anatoly & Fjellberg, Arne, 2006, Taxonomy of the Proisotoma complex. Redefinition of genera and description of new species of Scutisotoma and Weberacantha (Collembola, Isotomidae), Zootaxa 1382 (1), pp. 1-74 : 64-66

Strenzketoma buddenbrocki (Strenzke) comb.n.

Figs. 20 , 177–185

Proisotoma buddenbrocki Strenzke, 1954: 52 .

Material. More than 300 exx., Russia, Baltic Sea, the Gulf of Finland, Zelenogorsk (60 o 12’N 29 o 41’E), in plant debris decaying under sand, 25.viii.2002, leg. M. Potapov. 10 exx., Russia, Rostov Province, Azov Sea, shore near Zailov'ye village , 21.viii.1988, leg. A. Kremenitsa. 20 exx., Ukraine, W Crimea, Black Sea, sandy shore near Olenevka village (45 o 22’N 32 o 32’E), humid deep layer of sand, 21–28.vi.1994, leg. M. Potapov.

Redescription. Size up to 0.6 mm. Colour light yellow, ocelli patch and tip of antennae black. Integument with clearly visible primary granulation. Some areas on head and the body surface with more or less developed secondary granulation ( Fig. 179 ). Ocelli large, 8+8, G and H smaller. PAO wide and asymmetric (its upper part wider), about 3 times as long as ocellus diameter and 1.6–2.3 as long as U 3 ( Fig. 179 ). Maxillary head strongly modified, Anurida -like: capitulum elongated, lamellae slender with few teeth ( Fig. 20 ). Maxillary palp simple with only one sublobal hair. Labrum with 1(3)/554 chaetae (the two lateral prelabral chaetae possibly moved to the lateral edges of labrum, Fig. 179 ). Ventral side of head with 3+3 postlabial chaetae. Labium with 5 papillae, A and C much lower than others. Number of guards on papilla E reduced (e 4 and e 7 absent) ( Figs. 179, 181 ). Ant.1 with 2 basal microsensilla (bms) and 2 thick ventral sensilla (s) ( Fig. 180 ). Ant.2 with 3 bms and 1 s. Ant.3 with 6 distal s (AO and two lateral s), bms absent. Sensilla on Ant.4 hardly differentiated, subapical organite small.

Chaetal cover oligochaetotic. Th.II–Abd.III with 5,4–5/3–4,33 axial chaetae. Macrochaetae not differentiated, those on Abd.V 0.2–0.3 as long as the segment length. Tergal sensilla small, set in the p-row, shorter than ordinary chaetae and slightly thickened ( Figs. 186, 187 ). Their number as 30/02224 (s), 10/001 (ms). Lateral pair of sensilla on Abd.V much thicker than medial ( Figs. 187 ). Thorax without ventral chaetae.

Unguis simple, without inner tooth. Ti.1–3 with 18-18-19 chaetae, T-chaetae absent. A and B-rows with 7 chaetae, C - row reduced (4–5 chaetae) ( Figs. 182–185 ). Clavate tenent chaetae on tibiotarsi absent. Ventral tube with 4(5)+4(5) laterodistal and usually 4 posterior chaetae. Tenaculum with 3+3 teeth and one chaeta. Anterior furcal subcoxa with 8–10 chaetae, posterior with 6–7 chaetae. Manubrium with 1+1 anterodistal chaetae, posterior side with 10–12+10–12 chaetae, each lateral lobe with 5 chaetae. Lateral lobes of manubrium armed with chitinized wings and fully fused to the main part ( Fig. 177 ). Anterior side of dens with 5–6 chaetae in the distal half ( Fig. 178 ). Posterior side of dens slightly crenulated, usually with 10–11 chaetae (4–5 basal, 3–4 outer, 2 inner and 1 subapical) ( Fig. 177 ). Mucro with two teeth and a distinct lateral lamellae. Ratio of manubrium: dens: mucro as 7.1–9.3: 4.9–6.3: 1.

Taxonomic remarks. In addition to the generic characters, Strenzketoma buddenbrocki is unique because of small body size, uncommon colouration, large PAO (ratio PAO/Unguis is the highest among species of the Proisotoma -complex), 3 postlabial chaetae and the shape of the lateral lobes on manubrium. These characters probably reflect an adaptation to the special conditions of the marine littoral environment.

Distribution. Littoral species of sandy shores of the north Atlantic coasts, the Baltic Sea, northern part of Black Sea and Azov Sea.

Figures

FIGURES 18–23. Maxillary head in Proisotoma minuta (18), Ballistura schoetti (19), Strenzketoma buddenbrocki (20), Scutisotoma karadagi sp.n. (21), Scutisotoma kolymica sp.n. (22), and “Proisotoma” ripicola (23) (1–6 maxillary lamellae).

FIGURES 177–185. Strenzketoma buddenbrocki. 177, furca, posterior view; 178, dens, anterior view; 179, head; 180, group of lateroventral sensilla (s) of Ant.1; 181, labial palp (A–E: papillae, note the small A and C, h: hypostomal projection); 182–185, tip of leg 2 (182–183) and leg 3 (184–185) (183 and 185 schematic).

FIGURES 186–187. Strenzketoma buddenbrocki. 186, chaetotaxy of Th.II–Abd.II; 187, general distribution of macrochaetae, sensilla and microsensilla on body.