Malenchus truncatus
Knobloch, 1976
Photo Gallery-Long's Peak, Rocky Mountain Nat'l Park

Holotype female: L =  0.40 mm; a = 23; b = 4.9; c = 6.3; V = 69%; stylet = 11 um; CSE (CSE = Cuticular striae in esophageal region) = 56; T/ABW = (Tail length divided by anal-body width) = 6.7
Allotype male: L = 0.39 mm; a = 24; b = 4.9; c = 5.1; T = 53; stylet = 10.6 um; spicules = 16 um, gubernaculum = 5 um; T/ABW = 7.0
Paratype females (8): L = 0.40 (0.38-0.42) mm; a = 21 (18-23); b = 5.2 (4.7-5.3); c = 6.2 (5.2-7.2); V = 69% (67-70%); stylet = 10.5 (10.0-11.9) um; CSE = 53 (49-56); T/ABW = 6.3 (5.9-7.2).
Paratype males (4): L = 0.40 (0.39-0.42) mm; a = 22 (19-24); b = 4.9 (4.7-5.2); c = 5.3 (5.1-5.6); T = 55 (52-59); stylet = 11.0 (10.0-11.4) um; spicules = 16 (15-16) um; gubernaculum = 5 um; T/ABW = 7.5 (6.8-7.9).

Female: Body usually straight or with slight ventral curve posterior to vulva.  Width of cuticular striae about 1.5 um in mid-body.  Fifty-six transverse cuticular striae in esophageal region.  Lateral field with two crenate incisures; field occupies about 1/6 body width and extends from midway between stylet knobs and metacorpus to near middle of tail  Cephalic region continuous with 5-6 transverse striae; no cephalic sclerotization observed.  Anterior end appears truncate.  Stylet length 11 um with knob slanting posteriorly.  Metacorpus ovoid with valve; basal bulb pyriform.  Excretory pore 5-6 um poterior from basal bulb.  Hemizonid not seen.  Vagina thick-walled.  In some specimens, vulva opening has more conspicous vulval flaps than observed in other species.  Poterior uterine branch slightly more than half the corresponding body width.  Ovary single, outstretched; spematheca ovoid, filled with spermatozoa.  Tail tapered to acute terminus, finely striated to tip.  Anus obscure.  Tail 1.1 times longer than vulva-anus distance, about 6-7 times anal body width.  No phasmids observed.
Male:  General morphology similar to that of female.  Cephalic region narrower than in female.  Testis single, outstretched; spicules and gubernaculum as illustrated.  Caudal alae adanal, finely crenate, typical of genus.
DiagnosisMalenchus truncatus differs from all known species in the genus by the truncate anterior end.  It is distinguished from A. andrassyi by continuous cephalic region with 5-6 transverse striae, fewer transverse cuticular striae in esophageal region, more posterior vulva, shorter tail with acute terminus.  M. andrassyi has contracted cephalic region, no cephalic striae, eighty cuticular striae in esophageal region, vulva at 55-64%, tail length 80-102 um, and, according to drawings, 10-11 times anal body width with rounded terminus.  Male of M. truncatus has longer stylet; shorter, less filiform tail. M. andrassyi male stylet length 8-9 um, filiform tail 12-13 times anal body width. From M. machadoi, the new species differs in size, cephalic region shape, and tail shape.  M. machadoi is 0.52-0.56 mm in length with definitely contracted and rounded cephalic region. tail 8.5-9.5 times anal body width with a more acute terminus.
Holotype: Female collected December 1974 by John Davenport. Slide T-249t deposited with the USDA Nematology Collection at Beltsville, Maryland, USA.
Allotype: Male. Slide T-250t. Data same as holotype.
Paratypes, females and males: Slide T-1745p, 1 female. Slide T-1813p, 1 male. Data same as holotype.  All other paratype slides in the Nematology Collection in Entomology Department, Michigan State University, E. Lansing, Michigan, USA.
Type habitat and locality: Soil under moss and leaf litter in low, bog-like area near woods in Michigan State University Water Quality Management Project site in East Lansing, Ingham County, Michigan, USA.
(Description- Knobloch, 1976)

DNA Sequences Obtained
Specimen: Collected:
RMNP-DFF-12-92 Long's Peak, Rocky Mountain Nat'l Park
RMNP-DFF-12-96 Long's Peak, Rocky Mountain Nat'l Park