Agrenia parkeri, Fjellberg, Arne & Bernard, Ernest C., 2009

Fjellberg, Arne & Bernard, Ernest C., 2009, Review of Agrenia Börner, 1906 with descriptions of four new species from North America (Collembola, Isotomidae), Zootaxa 2306, pp. 17-28 : 20-24

Agrenia parkeri n. sp.

Figs. 1 C, D, J; 4A, B.

Type material. Holotype (in ethanol, not sexed) and 25 paratypes (ethanol) from USA, Tennessee, Sevier County, Great Smoky Mountains National Park, Rainbow Falls Trail, N35o39.862', W 83o27.599', 06.VI.2007, moss along stream, elevation 1,372 m, A. Fjellberg, sample number 0 7.188. Holotype and 15 paratypes deposited in the National Museum of Natural History, Washington, D.C.; remaining paratypes deposited in the University of Tennessee Entomology Collection. Additional material collected in late winter to early summer from Swain County, Great Smoky Mountains National Park, Noland Creek headwaters drift net samples, 20.I.1993 to 11.V.1993 (see Bernard & Felderhoff 2007), and from the banks of many other coldwater streams on the North Carolina side of Great Smoky Mountains National Park (Haywood County: Purchase Knob, Cataloochee River; Swain County: Clingman's Dome; Buncombe County: Elk Pasture Gap), as well as other North Carolina specimens from Graham County (several locations along Cherohala Skyway) and Yancey County (Mt. Mitchell State Park).

Description. Size up to 2.1 mm. Colour olive, uniform, darkest on dorsal side. Legs, furca and sides of head paler. Antennae bluish red, paler towards base. No sharp mid-dorsal line on tergites. Specimens with pale ground colour usually with posterior edges of tergites narrowly darkened. Maxillae with short, unmodified lamellae densely packed with fine denticles; lamella 1 just passing tip of maxillary head. Large males with relatively longer antennae than females, up to 2.7 times length of head diagonal; in smaller individuals (juveniles) antennae about 1.5 times length of head diagonal. Sensilla of antennae normal, without particularly dense sensilla on the fourth segment. PAO oval, length about 1.3 times the diameter of nearest ocellus. Head shape in adults slightly prognathous ( Fig. 2 A). Head and thorax with mixed short and long setae, remainder of body with short, fine setae. In reproductive males setae of Abd. V–VI distinctly shortened. Setae along frontoclypeal edge slightly longer and denser than the rest of the frontoclypeal area. Ventral tube with 0–6 anterior setae on each side (usually 4 or 5), lateral lobes with 10–20 setae on each side, caudal side with more than 35 setae in large individuals. Retinaculum with more than 25 setae in large specimens. Claws long and slender, particularly in animals collected in summer. Winter animals with relatively longer tunica at base of claws ( Fig. 1 J): claw index 2.0–2.7 (winter), 2.8–4.5 (summer). Inner edge of unguis with small middle tooth. Mucro without lateral seta, in summer animals less curved and with larger apical tooth than in winter animals ( Figs. 1 C,D). Subapical seta on dens strong, reaching well beyond tip of mucro. Ventral lamella of mucro moderately widened in the middle.

Etymology. Named for Dr. Charles Parker, U.S. Geological Survey, whose collection of hundreds of this species in Noland Creek headwater drift nets stimulated large-scale surveys for Collembola in Great Smoky Mountains National Park.

Discussion. Among species without a mucronal seta, A. parkeri n. sp. is recognized by the moderate number of anterior setae on the ventral tube (the two northern species A. atroviridis and A. riparia usually have no anterior setae, at most 1–2 in A. riparia ), apical mucro tooth subequal to or smaller than subapical tooth (in A. agilis the apical tooth is much larger than the subapical tooth and body colour is not olive), and PAO longer than the diameter of the nearest ocellus (in A. cyanura the PAO is smaller, the ventral tube has more anterior setae, and colour is different).

The cyclomorphic (winter/summer) change in shape of claws and mucro is similar to that described for A. riparia ( Fjellberg 1986) . The allometric growth in antennae and modified setae in reproductive males also are seen in A. polymorpha .

Distribution and ecology. Apparently widely distributed at higher elevations of the southern Appalachian Mountains (750–1,980 m) where it may be collected in great numbers in moss and debris along cold water streams. Highest numbers near the Noland Creek headwaters (~ 1,700 m elevation) were collected in drift-net samples in late winter and early spring when snow still covered the ground ( Bernard & Felderhoff 2007, recorded as Agrenia sp.).

Figures

FIGURE 1. A-G, mucro shapes of Agrenia spp. A. A. extrema n. sp., lateral view; B. A. extrema n. sp., dorsal view; C. A. parkeri n. sp., winter form; D. A. parkeri n. sp., summer form; E. A. falcula n. sp., ventral view showing the broad ventral lamella; F. A. falcula n. sp., lateral view; G. A. tarashchukae n. sp. H-K, claws of hind legs. H. A. falcula n. sp.; I. A. tarashchukae n. sp.; J. A. parkeri n. sp., winter form; K. A. extrema n. sp. L-N, maxillae. L. A. extrema n. sp., ventral side (left) and inner side (right); M. A. agilis, inner side; N. A. falcula n. sp., ventral side.

FIGURE 2. Head shape in Agrenia spp. A. A. parkeri n. sp.; B. A. falcula n. sp., reproductive male.