Scutisotoma acorrelata Potapov, Babenko & Fjellberg, 2006

Potapov, Mikhail, Huang, Cheng-Wang, Gulgenova, Ayuna & Luan, Yun-Xia, 2020, New and little known Isotomidae (Collembola) from the shore of Lake Baikal and saline lakes of continental Asia, ZooKeys 935, pp. 1-24 : 1

Scutisotoma acorrelata Potapov, Babenko & Fjellberg, 2006 Figs 14-17

Material.

37 specimens. Russia, Buryat Republic, Eravninsky District, coast of Bolshaya Eravna Lake, 06.VI.2008, coll. A. Gulgenova; Buryat Republic, Kabansky District, shore of Lake Baikal, Posolskiy Sor Bay, near Baykalskiy Priboy, 51.91216°N, 106.13954°E, seaweed debris near water, 23.VIII.2011, coll. A. Chimitova and L. Vanyavina; Buryat Republic, Barguzin Valley, Alginskoye Lake, floatation of wet coarse sand and shingle at water edge, 03.VIII.2014, coll. M. Potapov, C.W. Huang, and A. Gulgenova.

Description of epitokous males with fully developed ejaculatory duct in shore of Lake Baikal.

Size ca. 1.2 mm, subequal to adult females. Macrosetae erect, slightly serrated, well developed on all body tergites and head. Three first segments of antennae with thickened setae (Fig. 16 ). In females, subadult males and juveniles macrosetae are only developed on thoracic (only lateral pair) and two last abdominal segments (Fig. 14 ). Number of macrosetae 3,3/3,3,3,3, their arrangement as common for Anurophorinae (in position Md, Mdl and Ml), apart from Abd.IV on which Mp and Mdl are in common position while macrosetae Ml is absent and Md shifted backwards and set in posterior row of setae. Common arrangement of macrosetae on Abd.IV for Anurophorinae shown in Fig. 18 . Ventral side of Abd.VI with two thin curved macrosetae (vs. of normal shape in females). Head with macrosetae at posterior edge, in ocellar field, and between antennae. Front of head slightly swollen (vary). Antennae bent downwards. Three first segments of antennae thickened. In fully developed variant Ant.1 with three spiny setae (sp), Ant.2 with one sp and two ventral trichobothria, Ant.3 with two sp, one ventral trichobothrium and few (two or three) male “spurs” (Fig. 15 ). Thicknesses of sp vary. Tibiotarsus 3 with setae X and B5 insignificantly modified, set in wider sockets than in female.

Remarks.

Considering the dimorphic species S. muriphila (Grinbergs, 1968) and S. stepposa (Martynova, 1975) (for details see Grinbergs (1968), Chimitova and Potapov (2011)), S. acorrelata is the third member for the genus Scutisotoma Bagnall, 1948 which shows well developed sexual dimorphism. Males of S. acorrelata are less modified than in the two other species and polymorphism was not evident in our material. In taxonomical terms, the presence of epitokous males is a character of low value at generic level. It is probably optional in several genera. At species level, the diagnostic value of epitokous males is questionable. In many genera of the family Isotomidae the epitokous males are probably more frequent than usually considered. The short duration of the reproductive instar may have left many epitokous forms undetected.

Distribution and ecology.

The species was described from shore of Lake Baikal ( Potapov et al., 2006) and was further recorded at saline Alginskoye Lake and freshwater Bolshaya Eravna Lake. It lives in seaweed debris and in coarse sand.

Figures

Figures 14 - 18. Scutisotoma acorrelata 14, 16 appearance of adult female (14) and adult male in reproductive stage (16) (pigmentation not shown) 15 Ant. 1 - 3 in adult male in reproductive stage, lateral view 17 macrosetae on Abd. IV in adult male of S. acorrelata 18 common arrangement of macrosetae on Abd. IV in Anurophorinae. Abbreviations: bms-basal micro s-seta, de-ductus ejaculatorius, s-s-seta, is, ls, os-inner, lateral, and outer s-setae of antennal organ, sp-spiny setae, vt-ventral trichobothrium, msp-male spurs, Md, Mdl, Mp, Ml-macrosetae of Abd. IV.