Triacanthella copelandi ( Wray, 1963 )

Bernard, Ernest C., 2015, Redescriptions of Hypogastruridae and Onychiuridae (Collembola) described by David L. Wray, Zootaxa 3918 (3), pp. 301-338 : 325-328

Triacanthella copelandi ( Wray, 1963)

Figs 16 , 17

Clingmantha copelandi Wray 1963: 101 .

Triacanthella copelandi Christiansen & Bellinger 1980: 203 ; 1998: 215.

Specimens examined. Ten slides labeled “ type series”, designated here as lectotype female and 8 paralectotypes (2 males, 3 females, 3 juvenile or undetermined), USA, Tennessee, Sevier County, 27 October 1959, elev. 975 m, sample Tenn #621, hemlock litter ( Tsuga canadensis ), T. P. Copeland, coll., and one paralectotype, sex undetermined, same data except collected along highway to Newfound Gap, elev. 1219 m. Additional specimens examined: 4 juveniles, USA, Alabama, Shelby County, Oak Mountain State Park, 22 April 1961, hollow yellow poplar ( Liriodendron tulipifera ), H. R. Steeves, coll.; 1 male, 3 females, USA, North Carolina, Swain County, Great Smoky Mountains National Park, Indian Gap, elev. 1,634 m, UTM 3943336N 278648E, pitfall #28, 29 November–18 December 2000, I. Stocks, coll.; 1 female, USA, Tennessee, Cocke County, Great Smoky Mountains National Park, Albright Grove, pitfall #83, UTM 3956563N 293741E, elev. 1,033 m, 13 January–16 February 2001, I. Stocks, coll.

Redescription. Body length up to 2 mm. Color light pink in life, gradually fading in ethanol to white. Eye patches black. Granulation coarsest on Abd. VI ( Fig. 16 J); granule width on Abd. V 2.2–2.7 Μm. Chaetotaxy strongly but variably plurichaetose on Th. I–III and Abd. I–III ( Figs. 16 B, D), with numerous microsetae scattered mostly symmetrically among regular setae. Longer head and body setae sparsely, coarsely serrate ( Fig. 16 G). Extra setae on head primarily laterally and along posterior margin ( Figs. 16 A, C, E); seta a0 occasionally absent ( Fig. 16 C), sd setae sometimes missing or asymmetrical ( Figs. 16 C, E). Sensilliform setae increasing in length more posteriorly but always shorter than neighboring p2 and p4 setae. Pronotum with 8–16 setae ( Figs. 16 C, E, F). Mesonotal and metanotal chaetotaxy variable, from incomplete a-row and m-row setal rows ( Fig. 16 B) to full setal complement ( Fig. 16 D); setae m4 and p4 shifted anteriorly; setae p2, p3, p5 and p6 longer than other notal setae. Setae p2, p4 and p6 on Abd. I–V stout and either blunt or capitate ( Figs. 16 B, D). On Abd. VI setae a0–a2, m1 and p1 capitate; p2 acuminate ( Fig. 16 J). Subcoxae I, II, III with 2, 4, 6 or 3, 4, 5 setae, respectively, one seta on each subcoxa stout and blunt or capitate.

Antennal segments III and IV partially separated. Segment IV without apical vesicle but with finely granulated, slightly swollen apex ( Figs. 17 D, E); sensilla not differentiated from numerous sensilliform setae on all faces of segment; subapically with one recurved sensilliform seta and two socketless pin setae ( Fig. 17 E); ventral sensory field represented by 5 or 6 scattered, short sensilliform setae ( Fig. 17 E); organite capitate, set in pit ( Fig. 17 D), microsensillum peg-like ( Fig. 17 E). Sense organ of Ant. III with two small clavate, granulated sensilla flanked by two longer linear sensilla ( Fig. 17 D); microsensillum peg-like, inserted at proximal end of long groove. Eversible sac between Ant. III and IV absent. Ant. I with 10 longer setae in whorl, 4 proximal dorsal microsetae in transverse row; Ant. II with 11 longer setae in whorl, 4 proximal dorsal microsetae in transverse row.

Ocelli 8+8, ocelli G and H smaller than other ocelli ( Figs. 16 A, C, E). Postantennal organ diameter equal to or slightly greater than nearest ocelli, with 4 or 5 small, finely granulated lobes ( Figs. 17 A–C); accessory tubercle not seen. Anterior edge of labrum smooth, rounded-truncate; proximal two-thirds of labrum finely granulated with scattered larger tubercles; setal formula 5-4-4. Lamellae 1 and 2 of maxilla extending past capitulum teeth, denticles of marginal fringes simple, not grouped; “toothbrush” present ( Fig. 16 H). Outer lobe of maxilla without sublobal hairs. Sensilla A–E of labial palpus slender, longer than guard setae ( Fig. 16 I); guard setae a1, b1, e2 and lateral papilla papilliform with rounded apices; b2 and d2 spine-like; guard setae d1, d4, e1, e3, e5 and e7 absent; remaining guard setae slender, pointed. Labial palpus with six proximal setae.

Tibiotarsus I, II, III with 19, 19, 18 setae, respectively, each tibiotarsus with one clavate tenent hair (seta A4) ( Figs. 17 F, G). Unguis with two inner teeth in medial region, lateral teeth absent; unguiculus with slight basal swelling and slender apical filament reaching proximal inner tooth.

Ventral tube with 11+11 setae. Dens length about 4 times that of mucro; dorsal surface of dens with weak longitudinal grooves and partial tubercles; dens with 13 or 14 setae, three most proximal setae slender, acuminate; distal 10 or 11 setae thickened in basal third, then abruptly narrowed and more slender in distal two-thirds ( Figs. 17 H, I); apex of dens with prominent ventral eversible sac. Mucro with finely granulated basal lobe, partially granulated mid-dorsal triangular tooth and small apical tooth formed by upturned apex. Tenaculum with 3+3 teeth. Three anal spines, dorsal pair thick, curved, on short papillae; terminal spine straight, not on papilla, shorter than other anal spines ( Fig. 16 J).

Remarks. Triacanthella copelandi , the only member of the genus known from temperate North America, has been reported from the southern Appalachians (Tennessee, North Carolina) and the edge of the Cumberland Plateau (White County, Tennessee). Christiansen & Bellinger (1980) observed major differences between specimens they studied from White County and Wray’s description of 1963. After examination of Wray’s types it is clear that Wray missed some characters that Christiansen & Bellinger observed in their White County specimens: a prominent sac at the dens terminus, lack of an apical antennal bulb, and shorter anal spines than illustrated by Wray. The unusually long anal spines drawn by Wray may have been due to juxtaposition of the anal spines and the stout, clavate setae on Abd. VI. Other misinterpreted characters include the size of ocelli G and H, which were illustrated as equal or almost equal to ocelli A‒F but actually are reduced. Christiansen & Bellinger (1980) illustrated 9 and 12 setae on dentes of White County specimens, whereas those observed in this study had 13 or 14 setae.

Triacanthella copelandi possesses an unusual form of seta on the dens, where the setae are abruptly constricted at about the basal one-third. This character state apparently has not previously been reported in species of Triacanthella .

Figures

FIGURE 16. Triacanthella copelandi. A ‒ D) Dorsal chaetotaxy. A, B) Lectotype, pronotum not illustrated. C, D) Female from Indian Gap. E) Cephalic and pronotal chaetotaxy of female from Albright Grove. F) Pronotal chaetotaxy of male paralectotype. G) Longer setae of head. H) Maxilla, specimen from Indian Gap; numbers identify lamellae, t = “ toothbrush ”. I) Labial palpus. J) Lateral view of sixth abdominal segment, Albright Grove specimen.

FIGURE 17. Triacanthella copelandi. A ‒ C) Left and right postantennal organs and anterior ocelli. A) Lectotype. B) Specimen from Indian Gap. C) Specimen from Albright Grove. D) Dorsal aspect of third and fourth antennal segments, lectotype. E) Ventral aspect of third and fourth antennal segments, lectotype; arrows indicate “ pin ” setae. F) Foretibiotarsus, lectotype. G) Metatibiotarsus, lectotype. H) Dens and mucro, lectotype. I) Dentes and mucrones, Indian Gap specimen.