Misturasotoma, Bernard & Christiansen, 2010

Bernard, Ernest C. & Christiansen, Kenneth A., 2010, Misturasotoma, a new nearctic springtail genus (Collembola: Isotomidae), Zootaxa 2499 (1), pp. 57-62 : 58-61

Misturasotoma new genus

Diagnosis. Isotominae with all abdominal segments clearly separate ( Fig. 1 ). Eyes absent. Postantennal organ elongate-elliptical. Antenna without apical bulb or clearly differentiated blunt setae. Tenaculum quadridentate with 9–15 setae on corpus. Unguis with prominent inner tooth and pair of external dorsal teeth. Unguiculus with prominent corner tooth. Manubrium with many setae on both dorsal and ventral surfaces; some apical setae spine-like. Dentes slender, tapering, dorsally crenulate and about twice as long as manubrium, with many ventral setae. Mucro quadridentate with all teeth well developed. All body setae smooth and acuminate; abdominal sensilliform setae short, thin.

Type species: Isotoma brucealla Wray 1953b .

Discussion. Wray (1953a) originally described this species as Isotoma brucei but upon discovery of a previously described Isotoma brucei ( Carpenter, 1907) , now Archisotoma brucei , changed the name to I. brucealla ( Wray 1953b) . In Potapov (2001) this genus will key to Heteroisotoma but differs in having smooth rather than ciliate setae and an oval PAO with thin walls rather than a narrow PAO with thick walls. The arrangement of the abdominal sensilla also seems to differ from Heteroisotoma in that the type species has anterior sensilliform setae on Abd. IV and 3+3 anterior sensilliform setae on Abd. V; Heteroisotoma spp. lack anterior sensilliform setae on Abd. IV and have 2+2 anterior sensilliform setae on Abd. V.

Etymology. From the Latin mistura = mixture and Isotoma , referring to the mixture of characteristics of different genera of Isotominae found in the genus.

Misturasotoma brucealla ( Wray 1953a)

Figs. 1–21

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Isotoma brucei Wray, 1953a: 66 (nec Carpenter 1907: 474).

Isotoma brucealla Wray, 1953b: 55 .

Isotoma (Desoria) brucealla Christiansen & Bellinger, 1981: 718 ; 1998: 797.

Parisotoma brucealla Bellinger et al., 1996 –2010: www.collembola.org.

Material examined. Lectotype, USA, Utah, Monte Cristo , 15 July 1951, pocket gopher nest, G. F. Knowlton and T. T. Tibbetts, colls . Paralectotype, same data except collected 18 July 1951. Both specimens are deposited in the North Carolina State University Entomology Collection , Raleigh , North Carolina, USA. One specimen collected from USA, Washington, Skamania County, lava tube cave, is deposited in the Grinnell College , Grinnell, Iowa, Collembola collection .

Redescription. Colour: “Yellowish-white…with traces of black pigment over head and body in the pattern of small grouped areas of punctiform pigment…” ( Wray 1953a). Labrum with 5–5–4 setal arrangement; apex of labrum rounded-trapezoidal with four subapical tubercles and a slightly more proximal transverse ridge ( Fig. 5 ). All maxillary lamellae short, none exceeding tips of capitular teeth. Labial palpus ( Fig. 3 ) with 4 proximal setae and all guard setae except e 7; lateral papilla minutely granulated on basal twothirds, smooth apically. Hypostomal papilla ( Fig. 4 ) with apical seta and two proximal unsocketed setae. Maxillary palpus ( Fig. 2 ) with long apical seta, four unsocketed setae, and one socketed basal seta. First antennal segment ventrally with loose cluster of 6–8 pointed setulae. Sense organ of Ant. III with two slender, weakly bent or straight sense clubs in shallow groove, two similar sensilla subventrally, and three longer, slightly more proximal sensilla ( Fig. 8 ). Fourth antennal segment with numerous slender sensilliform setae not sharply distinguished from typical setae; subapical sense rod long, slender, pointed; pin seta broadly conical basally, slender distally, with small linear secondary seta near base ( Fig. 9 ). P.A.O. elongate-elliptical, with 4 guard setae ( Fig. 6 ). Eyes absent. Length of lectotype 1.6 mm, paralectotype 2.1 mm.

Each tibiotarsus with 11 apical setae, tenent hair acuminate ( Figs. 9, 10, 12 ). Unguis with strong ventral tooth and two subdorsal teeth not forming a tunica, one longer and stronger than the other; unguiculus with strong inner tooth and on some legs with small basal tooth; unguicular tip narrowly rounded ( Figs. 9, 10 ). Unguis broad in ventral view ( Fig. 11 ). Abdomen with third and fourth segments about equal in length; fifth and sixth segments clearly demarcated. Ventral tube with 24 (10+14) setae ( Fig. 13 ). Tenaculum with 9–13 setae ( Figs. 14, 15 ). Ventro-apical manubrial setae spinelike, slightly thicker than other manubrial setae ( Fig. 16 ). Dens about 2.5 times longer than manubrium, with 8 dorsal setae proximally and in mid-region, without seta in distal region ( Fig. 17 ); ventro-apical seta reaching to level of mucronal basal teeth. Mucro quadridentate, apical and subapical teeth subequal in size; basal teeth smaller, lateral, not aligned with subapical tooth ( Figs. 18, 19 ).

All setae smooth. Macrochaetae distinctly developed only on last three abdominal terga, each with 3+3 macrochaetae ( Figs. 20, 21 ). Macrochaetae of last two abdominal segments about 2.5 times length of unguis. Sensilliform setae of Abd. IV and V of lectotype distributed as follows: Abd. IV, 2+2 anterior, 0+1 medial, 8+8 posterior; Abd. V, 2+3 anterior, 3+4 posterior ( Fig. 20 ). On Abd. V of paralectotype, 2+2 anterior, 3+3 posterior sensilliform setae ( Fig. 21 ). Arrangement and number of sensilliform setae on other segments not determined.

Remarks. The extremely flattened, partially twisted condition of the type specimens did not allow for an accurate determination of sensilliform seta distribution on segments anterior to Abd. IV. Sex of the types is unknown, as the genital aperture of each specimen was obscured by the overlapping abdominal terminus and extended furcula. Likewise, several features, e.g., the ventral tube chaetotaxy and the mouthparts, could only be determined from one of the specimens. The lectotype was chosen for the clarity of the abdominal chaetotaxy and antennal structures, even though it is significantly shorter than the paratype and possibly is an immature specimen.

The exact type locality of this species is unknown. In Utah, “Monte Cristo” currently refers to a large recreational area and snowmobile trail north of Huntsville, Utah, in the Uinta-Wasatch-Cache National Forest . It is also the name of a mountain range in the same area .

Christiansen & Bellinger (1981, 1998) based their understanding of M. brucealla on a specimen collected from a lava tube in Washington, as the type specimens were unavailable at the time. This specimen was reexamined and found to be very similar to the M. brucealla types except that the ungues are more slender. The arrangement of the visible sensilliform setae of Abd. IV and V appeared to be compatible with that of the types but could not be determined in its entirety. This specimen should still be considered to be M. brucealla .

Figures

FIGURES 1–15. Misturasotoma brucealla. 1. Habitus, lectotype. 2. Maxillary palpus, paralectotype. 3. Labial palpus, paralectotype. 4. Hypostomal lobe, paralectotype. 5. Apex of labrum, paralectotype. 6. Postantennal organ, lectotype. 7. Apex of fourth antennal segment, lectotype. 8. Sense organ of third antennal segment, lectotype. 9. Forefoot complex, lectotype. 10. Hind foot complex, paralectotype. 11. Hind foot, ventral view, paralectotype. 12. Hind foot complex, Washington specimen. 13. Ventral tube, ventral view, paralectotype. 14. Tenaculum, lectotype. 15. Tenaculum, paralectotype.

FIGURES 16–21. Misturasotoma brucealla. 16. Manubrium, ventral view, paralectotype. 17. Dens, dorsal view, lectotype. 18. Mucrones, lectotype. 19, Mucrones, paralectotype. 20. Chaetotaxy of Abd. IV and Abd. V tergites, right side, lectotype; typical setae not near sensilliform setae omitted. 21. Chaetotaxy of Abd. V and Abd. VI tergites, left side, paralectotype, only macrochaetae and sensilliform setae drawn.