Onychiurus mai Wray, 1950

Bernard, Ernest C., 2015, Redescriptions of Hypogastruridae and Onychiuridae (Collembola) described by David L. Wray, Zootaxa 3918 (3), pp. 301-338 : 332-335

Leeonychiurus mai (Wray, 1950) new combination

Figs. 20 , 21 A–C

Onychiurus mai Wray 1950: 91 .

= O. oreadis Mills, 1935 ; Stach 1954: 56, 77.

= Pseudonychiurus oreadis ( Mills, 1935) ; Salmon 1964: 188.

?= O. flavescens Kinoshita, 1916 ; Christiansen & Bellinger 1980: 451; 1998: 494, through synonymy with O. oreadis .?= O. millsi Chamberlain, 1943 ; Christiansen & Bellinger 1980: 451; 1998: 494.

Specimens examined. Neotype male (by present designation) and two females, USA, Idaho, Franklin, 1 April 1959, poplar leaves, G. F. Knowlton, coll.

Redescription. Length 1.3–1.7 mm [up to 1.5 mm]. [Color white.] Body slightly widened at Abd. III–IV, then tapering posteriorly to rounded terminus ( Figs. 20 A, C). Granulation simple, not segregated into distinctly different fields, granule diameter on head 2.2–2.4 Μm, on Abd. V 1.6–2.0 Μm. Anal spines conical, slightly curved dorsad, on short papillae ( Fig. 21 B). Dorsal chaetotaxy oligochaetotic, differentiated primarily into macro- and mesosetae. Sensillum-like setae not distinct from normal setae. Cephalic seta d0 present. Lateral microsensilla present on mesonotum and metanotum. Setae m2, p4, p6 and p7 on metanotum long ( Fig. 20 B). Seta m0 present on tergite V ( Fig. 20 C); setae a0 and p0 present on tergite VI ( Fig. 21 B). Mesosternum and metasternum each with 1+1 setae. Venter of Abd. VI terminus with five a-setae of similar length; setae b1 much longer than other b-setae; seta c2 at least twice the length of other c-setae ( Fig. 21 C).

Dorsal pseudocelli formula 32/133/33343; posterior cephalic pseudocelli visible in dorsal view ( Fig. 20 A); each subcoxa with one pseudocellus. Ventral pseudocelli formula 11/000/00010. Parapseudocelli and pseudopores not observed.

Antennal segment IV without apical vesicle or cauliflower-like protuberances ( Fig. 20 F). Most setae slender, sensillum-like. Subapical organite peg-like; microsensillum as a curved, blunt peg in pit at proximal third of Ant. IV. Sense organ of Ant. III with five guard setae, five papillae, two smooth sense rods, and two stalked, oval, morel-like (mulberry-like) sense clubs; microsensillum nearly level with papilla base ( Fig. 20 G). Antennal segments I, II, III with 9, 15, 14 ordinary setae, respectively. Labrum with wavy anterior edge of six lobes, the middle lobes the most distinct ( Fig. 20 I), labral setae not clearly observed. Maxilla ( Fig. 21 A) with bifurcated lamella 1 extending past capitulum teeth; lamella 2 reaching tips of teeth, denticulate on both edges; lamella 4 extending above 3, 5 and 6, its face covered with minute denticles. All sensilla of labial palpus present, sensilla A and C blunt (AC type) ( Fig. 20 H); guard setae a1, b1, b2 and d2 small, spines on short papillae; guard setae b4 and e3 weakly spatulate, other guard setae pointed; d1 and e4–e7 absent. Seven stout, straight proximal setae. Postantennal organ with 15 compound vesicles in wide groove ( Figs. 20 D, E).

Tibiotarsi I and II with 3 setae in proximal whorl, 8 setae in middle whorl, and 11 setae in distal whorl; tibiotarsus III with 2 proximal, 7 middle, and 11 distal setae. Unguis untoothed, granulate basally; unguiculus granulate basally with weak basal lamella, apical filament tapering and extending past middle of ungual inner margin Fig. 20 J). Tenent hair short, pointed. Ventral tube with two basal and five distal setae on each side. Male ventral organ absent. Furcal region oval, in middle of segment, finely granulated, with four posterior setae arranged in one row ( Figs. 20 K, L); manubrial setae arranged in three partially irregular rows.

Remarks. Specimens labeled as O. mai from the type locality were not found in the Wray collections and are presumed lost. The three specimens collected later at Franklin, Idaho, about 32 km from the type locality of Logan Canyon, Utah, labeled in Wray’s hand as O. mai and fitting the original description, were used for the redescription. The male specimen is designated as the neotype for the species.

As O. mai , this taxon has been tentatively synonymized with several other onychiurids, but differs from them in current generic placement. Wandaphorura millsi ( Chamberlain, 1943) has a PSO formula of 21/022/22233 ( Pomorski 2007). The PSO formula for O. oreadis Mills, 1935 , currently recognized as a junior synonym of Allonychiurus flavescens ( Kinoshita, 1916) ( Christiansen & Bellinger 1998) , was given as 32/122/33333 ( Mills, 1935). Allonychiurus flavescens has the same PSO formula as L. mai n. comb. ( Sun et al. 2009, 2011) but differs in generic characters.

These specimens fit well within the recently described genus Leeonychiurus Sun & Arbea, 2014 ( Sun & Arbea 2014), and therefore the species is transferred to that genus as L. mai (Wray, 1950) new combination. The dorsal PSO formula of L. mai is identical to that of L. fusongensis Sun & Arbea, 2014 , but ventrally L. mai has a single pair of pseudocelli only on Abd. IV, whereas L. fusongensis has ventral pseudocelli on Abd. II‒IV. The ratio of anal spine/claw is about 0.4 in L. mai but about 1 in L. fusongensis .

Figures

FIGURE 20. Leeonychiurus mai. A) Head, prothorax, mesothorax of female, dorsal view; d 0 = unpaired median seta. B) Metanotum of male, dorsal view. C) Abdominal segments of female, dorsal view. D) Postantennal organ. E) Optical crosssection of postantennal organ. F) Tip of antenna. G) Sense organ of third antennal segment and enlargement of sense club. H) Labial palpus. I) Anterior edge of labrum. J) Apex of hind tibiotarsus. K) Ventral view of fourth abdominal segment, female. L) Ventral view of fourth and fifth abdominal segments, male.

FIGURE 21. Onychiuridae. A – C) Leeonychiurus mai. D – F) Heteraphorura magnina. G ‒ J) Onychiurus wilchi. A, D, G) Maxillae. B, E, H) Dorsal terminus of sixth abdominal segment. C, F) Venter of sixth abdominal segment. I) Sense organ of third abdominal segment, sense clubs not shown. J) Distal part of hind tibiotarsus.