Spinonychiurus alaskensis, Pomorski, Romuald J. & Kapruś, Igor J., 2015

Pomorski, Romuald J. & Kapruś, Igor J., 2015, Revision of the genus Spinonychiurus Weiner 1996 (Collembola: Onychiuridae) with description of five new species, Zootaxa 3914 (2), pp. 101-121 : 115-118

Spinonychiurus alaskensis sp. nov.

( Figs 58–64 )

Type material. Holotype (female mounted on slide) and 4 paratypes (2 unreproductive males, 2 females mounted on two slides); litter of dry mixed forest ( Alnus + Populus + Betula); 12.ix.1976; Chena Ridge, Fairbans, Alaska, USA, leg. A. Fjellberg (preserved in the collection the Department of Biodiversity and Evolutionary Taxonomy, Zoological Institute, Wrocław University, Wrocław).

Etymology. Named after the type locality – Alaska.

Description. Color white. Body length of females 0.85–1.0 mm, unreproductive males – 0.85 mm. Body shape cylindrical with curved anal spines as long as hind claw ( Fig. 58 ). Granulation of body surface fine and uniform, distinctly stronger only around pseudocelli on the front of head. Antennal bases not marked.

Antennae nearly as long as head with typical Subapical organite. Antennal segment IV with two well marked sensilla (dorsal-subapical, internal-subbasal). Microsensillum on antennal segment IV in latero-external position, distinctly above of first proximal whorl of chaetae ( Fig. 59 ). Antennal III sensory organ with 5 guard chaetae, 5 papillae, 2 small sensory rods and 2 sensory clubs feebly bent, smooth with poorly marked longitudinal ribs ( Figs 59, 60 ). Microsensillum located slightly below antennal III sensory organ.

Postantennal organ consists of 10–12 granulated vesicles ( Fig. 61 ). Labial palp of A type.

Pseudocellar formula: dorsally 32/122/33343, ventrally 1/000/0000. Subcoxae1 of I–III legs with 1 pseudocellus each. Parapseudocellar formula: 1/000/ 122103 (each anal valve with parapseudocellus). Localization of parapseudocelli on abdominal sterna I–VI as in Fig. 64 . Subcoxae1 of I–III legs with 1 parapseudocellus each.

Dorsal chaetotaxy as in Fig. 58 , nearly symmetrical, poorly differentiated into meso- and microchaetae. Thoracic terga II and III with microsensilla laterally. Body sensory chaetae s well differentiated according formula: dorsally 1/011/ 111021, ventrally 2/000/0001. Thoracic tergum I with 7–8 + 7–8 chaetae. Abdominal tergum IV with p0 and m0 chaetae. Abdominal tergum V with a0, p0 and m0 chaetae. Abdominal tergum VI with 2 axial chaetae (a0 and p0) and 1+1 prespinal chaetae. Subcoxae1 of I–III legs with 4, 5, 5 chaetae respectively.

Thoracic sterna with 0+0, 1+1, 1+1 chaetae respectively. Ventral tube of females with 6–7 + 6–7 chaetae, and 4+4 chaetae at base ( Fig. 64 ). Furca reduced to small area of fine granulation and three rows of manubrial chaetae behind its posterior edge ( Fig. 62 ). Claws without teeth. Empodial appendage with short but distinct basal lamella, a distinctly shorter than inner edge of claw (ratio 0.5–0.6). Tibiotarsi I–III with 7 chaetae in distal whorl ( Fig. 63 ). Ventral organ is not found in unreproductive males.

Remarks. So far S. alaskensis sp. nov. is the only Nearctic member of the genus and is characterized by two exceptional characters: the presence of 7 chaetae in distal whorl of tibiotarsi and presence of 4+4 chaetae at base of ventral tube. Within the genus it has probably an isolated position, but the presence of basal lamella on empodial appendage, distinct body sensory chaetae s and typical subapical organite suggest relationship with European member of the genus– S. subedinesis .

Figures

FIGURES 58 – 64. Spinonychiurus alaskensis: 58, habitus, dorsal chaetotaxy and localization of pseudocelli; 59, antennal segments III – IV, antennal III sensory organ; 60, sensory clubs of antennal III sensory organ; 61, postantennal organ and pseudocelli at base of antenna; 62, remnant of furca; 63, tibiotarsal chaetotaxy and claw of legs III; 64, abdominal sterna I – VI, chaetotaxy and localization of pseudocelli and parapseudocelli.