Thalassaphorura duplopunctata

Thalassaphorura duplopunctata (Strenzke 1954) (Figures 5 and 6) Material examined Thirteen females and 13 males, Zhifu island, 37°36 ′ N, 121°24 ′ E, shingly beach (No. 23–26, 28–34, 40–42, 45–47), Yantai City, 21 April 2011, leg. Y. Bu, C.W. Huang, M. B. Potapov and N.A. Kuznetsova; 2 males, Yangma island, 37°27 ′ N, 121°36 ′ E, shingly beach (No. 70), 22 April 2011, leg. Y. Bu, C.W. Huang, M.B. Potapov and N.A. Kuznetsova. 20 individuals (10 females and 10 males) are deposited in SIPPE, 2 (1 female and 1 male) in MSPU, and 4 (2 females and 2 males) in NEIGAE. We also studied the materials of populations of T. duplopunctata from several locations in the northern European part of Russia (Murmansk coast and Dolgy Island) and Far East (coast near Magadan), all leg. Babenko. Description based on Chinese specimens Size 1300–1460 µm in females, 1100–1350 µm in males. Body subcylindrical, body sides almost parallel. Pseudocellar formula: 32/233/33343 dorsally, 11/000/01110 ventrally (Figures 5C–E, 6D), subcoxa 1 of legs I–III with two, two and two pso respectively. Parapseudocelli absent. Pseudopore formula: 00/011/11110 dorsally, 00/111/000x00 ventrally. S-chaetae not distinguishable from ordinary chaetae. Tiny and blunt ms, present on Th. II–III. Head. Antennae slightly longer than head. Length ratio of Ant. I: II: III: IV as about 1: 2: 2: 2.5. Ant. IV with subapical organite with apex globular; basolateral ms at about half length from base (Figure 6C). Ant. III sensory organ composed of five papillae, five guard chaetae, two small sensory rods and two smooth subequal clubs, and a lateral ms (Figure 5B). Ant. II with 13 chaetae. Ant. I with nine chaetae. Antennal base with distinct granulation. PAO composed 18–22 simple vesicles (Figure 5A). Dorsal cephalic chaeta d0 present. 3 + 3 p-chaetae present between two inner posterior pso, p1 anterior to others (Figure 5C). Mandible with strong molar plate and four apical teeth. Maxilla bearing three teeth and six lamellae. Maxillary outer lobe with a simple palp, one basal chaeta and two sublobal hairs. Labral chaetae formula 4/142 (Figure 6B). Labium with six proximal, four basomedian (E, F, G, f) and six basolateral (a, b, c, d, e, e’) chaetae; labial type AC, papillae A–E respectively with 1, 4, 0, 3 and 2 guard chaetae (Figure 6A). Postlabial chaetae 4 + 4 along ventral groove. Body chaetotaxy (Figures 5C–E, and 6D). Ordinary chaetae differentiated in mesochaetae and macrochaetae. Th. I tergum with 7–8 + 7–8 chaetae. Th. II–III terga with 4 + 4 chaetae and Abd. I–II terga with 3 + 3 chaetae respectively on both side of axial line, without axial chaeta. Chaetae of Abd. III–V terga asymmetrical (more pronounced in males), Abd. VI tergum with one axial chaeta (m0) (Figure 5D, E). Th. I, II and III sterna with 1 + 1, 1 + 1, 1 + 1 chaetae respectively. Appendages. Subcoxa 1 of legs I–III with 4, 4 and 4 chaetae, subcoxa 2 with 1, 4 and 4 chaetae, respectively. Tibiotarsi of legs I, II and III with 18 (1, 8, 9) chaetae each. Unguis without teeth. Unguiculus 0.7 times as long as inner edge of unguis, with inner basal lamella (Figure 6E). Ventral tube with 1 + 1 anterior chaetae, 6– 8 + 6–8 distal chaetae, 2 + 2 basal chaetae. Furca reduced to a field of fine granulation and with four small dental chaetae arranged in two rows below; only one manubrial row of chaetae present (Figure 6D). Genital plate with 16–18 chaetae in females, 30–52 chaetae in males. Male organ absent. Anal valves with numerous acuminate chaetae; each lateral valve with a0 and 2a1; upper valves with chaetae a0, 2b1, 2b2, c0, 2c1, 2c2. Anal spines set on distinct papillae, 0.7 times as long as inner edge of hind unguis. Variation Two females from China were found with additional pso on the ventral side of Abd. IV (only on one half in one of the females). Ecology From the middle part of intertidal zone to the supralittoral part of shingly beaches. Remarks Thalassaphorura duplopunctata is distributed in the Arctic and boreal areas of the Holarctic. Its scarce records in Eastern Palaearctic and Nearctic are probably the result of insufficient knowledge of littoral Collembola of the northern Pacific compared with respective areas of the Atlantic, which have been studied in more detail (Figure 7). Considering Shandong Province to be the most southern record of this primarily northerly distributed species, we give its full description here.Published as part of Sun, Xin, Gao, Yan & Potapov, Mikhail B., 2013, Review of Chinese littoral Thalassaphorura (Collembola: Onychiuridae), with the description of two new species, pp. 575-589 in Journal of Natural History 48 (9 - 10) on pages 583-586, DOI: 10.1080/00222933.2013.839843, http://zenodo.org/record/463158