Female: On specimens killed by gentle heating, habitus slightly and regularly ventrally curved. Body thin, elongated, slightly tapering at anterior extremity; posterior extremity long conical. Cuticle thin (0.5 um); transverse striation narrow (1.1 um at mid-body). Lateral field composed of four equidistant lines, 6-9 um wide at mid-body, not areolated except at its anterior part and on the tail. Labial area dome-shaped, with three or four annules, not separated from the rest of the body. SEM: face plain; labial sectors fused together and fused with the labial disc; amphidial aperture a large slit; oral aperture ovate, surrounded by six pits (apertures of the inner labial sensillae). Cephalids not seen. Stylet straight; basal knobs rounded or slightly sloping backward. Dorsal oesophageal gland opening at 3-4 um from base of stylet. Procorpus long and thin; median bulb well marked, ovate, occupying about half of the corresponding body diameter, with prominent valve; isthmus long and thin; oesophageal glands online, elongated, with long ventral overlapping intestine; oesophageal glands nuclei line-up, the posterior (dorsal gland) somewhat larger. Intestine without fasciculi, forming a very short post-anal sac. Nerve ring encircling the anterior half of the isthmus. Excretory pore at 95-128 um from anterior end. Hemizonid flat, 3-4 um long, 2-5 um anterior to excretory pore. Hemizonion lenticular, 1.5-2 um wide, 11-19 um posterior to excretory pore. Vulva plain; vulval lips slightly protruding; no lateral flaps, no epiptygma. Anterior genital branch straight; ovary with oocytes in one row; spermatheca rounded, in-line with genital tract, thick walled, containing globular spermatozoa 2 um in diameter; columnar uterus of medium length. Posterior genital branch reduced, 46-74 um (59) long and degenerated, in which only the columnar part of the uterus can be recognized; in some cases, a cell with a prominent nucleus (remnant of the cap cell of the ovary?) is present at the distal end. Tail long conical; extremity variable, from more or less pointed to stout, but always showing a terminal projection and a terminal thickening of the cuticle; lateral field areolated on the posterior two thirds of the tail, the four lines nearly reaching the tail extremity. Phasmids punctiform, 17.5-35 um (26.5) posterior to anus or at 37-54 % (46) of the tail length. Caudalids rarely seen, 1.5-2 um long, 2-3 um anterior to anus.
Male: Similar to female except for smaller body and stylet length. No secondary sexual dimorphism visible in labial area or oesophagus. Spicules curved, cephalated; gubernaculums thin, anteriorly recurved, slightly projecting from cloaca. Caudal alae well developed, crenate, enveloping tail extremity. Tail conical, extremity pointed. Phasmids 12-23 um (17) posterior to anus, or 30-56 % (43) of tail length, located in a notch on the edge of the caudal alae.
Type Host and Locality
Roots and surrounding soil of Plagiobothrys stipitatus var. micranthus, vernal pond near Farmington, San Joaquin Co., California, USA (coll. & leg. : A. Moretto).
Holotype (female) deposited in the collection (UCRNC) of the Department of Nematology, University of California, Riverside, USA.
Paratypes distributed in the following collections: Muséum national d’Histoire naturelle, Laboratoire des Vers, Paris, France: six females, three males; USDA Nematology Investigations Beltsville, Maryland, USA: three females, two males; Rothamsted Experimental Station, Harpenden, U.K. : three females, two males; Landbouwhogeschool, Laboratorium voor Nematologie, Wageningen, Nederland: three females, two males. Remaining type material in the UCRNC, Department of Nematology, University of California, Riverside, USA.
Diagnosis and Relationships
Pratylenchus morettoi n. sp. differs from the 61 known species in the genus by the thin, well marked projection at the tail terminus.
Some Pratylenchus species, such as P. irregularis Loof, 1960 (now considered as a junior synonym of P. pratensis (de Man, 1880) Filipjev, 1936), P. goodeyi Sher & Allen, 1953 and P. ventroprojectus Bernard, 1984, have a tail terminus which is not regularly rounded but which have a ventral or median projection, although the projection is short and stout, and not well marked.
In addition to the above mentioned characters, P. morettoi n. sp. has other characters which are not common in the genus: body thin and elongate, lip area domeshaped, long oesophageal overlap with the intestine, tail elongate and more conical than cylindrical.