Stylet Knobs Research Articles

Tylenchorhynchus Aspericutis N. Sp. (Nematoda) From Mexico With an Emended Description of Psilenchus Hilarulus De Man, 1921 and Two Intersexes

Tylenchorhynchus aspericutis n. sp. is described from the state of Chihuahua. T. aspericutis is compared with T. latus from which it differs in smaller size, cephalic region offset with three annules, stylet knobs slanted posteriorly, eleven-twelve tail annules, spermathecae and presence of males. A Chihuahua variant population of T. mexicanus is described. Variations in several populations of Psilenchus hilarulus de Man, 1921 and an emended description of P. hilarulus is presented. Two intersexes of P. hilarulus are described.

The Usefulness of Some Larval Dimensions To Distinguish Heterodera Rostochiensis and H. Pallida

More than 98 % of Norwegian populations of round-cyst nematodes attacking potatoes are H. rostochiensis pathotype A. Others having yellow females are similar or identical to Dutch pathotype B and C. Most populations of H. pallida have white females and are Dutch pathotype D, British E. One population with cream females is evidently British pathotype B. The discrimination of H. pallida populations on the base of white females showed to be reliable. On average larvae from populations of this species were larger than from populations of H. rostochiensis for all characters measured. A ratio (R) of the component of variance between species to the total variance for measure of six larval dimensions, are tabulated. Particularly high value of R is shown for stylet length. For this measurement little is gained by measuring more than two specimens to identify populations of pure species. The distance from the tip of the head to the base of the stylet knobs is a slightly poorer discriminant and that from the medium bulb plates to the excretory pore is poorer still for a single measure. If more than ten specimens are measured within each population, however, the latter is the most reliable measure of all the characters investigated. Measurements of the length of the shaft and the basal knobs, the length of the clear tail area, and especially body length are all unreliable in distinguishing between species.

Heterodera Pallida N. Sp. (Nematoda: Heteroderidae), a Second Species of Potato Cyst Nematode 1)

The pathotypes of Heterodera rostochiensis Woll. 1923 with white or cream females are described as a new species, Heterodera pallida, subgenus Globodera Skarbilovich, 1959, from England. It differs from H. rostochienis in having a larger second stage larva with a stylet on average about 23 μm long (21 μm in H. rostochiensis) and basal stylet knobs pointed anteriorly (rounded in H. rostochiensis); in having cysts with Granek's ratio less than 3.0 (greater than 3.0 in H. rostochiensis) and only 8 to 20 cuticular ridges between anus and fenestra (16 to 31 in H. rostochiensis) and in having females that remain white or cream (golden yellow in H. rostochiensis).

Some Remarkable Tylenchida From Korea

Four species of Tylenchida from Korea are discussed: Hemicriconemoides varionodus n. sp. is characterized by rounded stylet knobs, 102-112 body annules, continuous rounded lip region and conical tail. A second population of Merlinius koreanus contained males with a variable bursa structure; one of them showed a tail resembling that of the female. One male of Eutylenchus africanus was present and Rotylenchus orientalis, exceptional for the posterior position of vulva and dorsal oesophageal gland opening, was also found.

Electron Microscopical Studies On Ditylenchus Dipsaci Ii. Oesophagus

The three main components of the oesophagus of Ditylenchus dipsaci are the oesophageal wall, the lumen, the associated membranes collectively referred to here as the oesophageal lumen complex, and the dorsal and two subventral glands. The oesophageal wall is not a syncytium. In cross-section the wall of the procorpus consists of two cells anteriorly and four posteriorly. There are twelve cells in the metacorpus, six of which are muscle cells. Only the basement membrane remains of the wall of the isthmus. The wall of the postcorpus is of uneven thickness and serves as an elastic sac for the three glands. The oesophageal lumen is cylindrical from the base of the stylet knobs to the valve of the metacorpus. It is triradiate from the valve to the oesophago-intestinal junction. The lumen is surrounded throughout its length by eight or nine pairs of membranes. It is the subdorsal and ventral extensions of the membranes that produce the triradiateness of the oesophagus. The dorsal gland is a separate entity but the two subventral glands become fused in the anterior half of the postcorpus. A valve is present at the oesophago-intestinal junction.

Three New Species of the Genus Meloidogyne Goeldi, 1887 (Nematoda: Heteroderidae)

Meloidogyne deconincki n. sp., M. litoralis n. sp. and M. oteifae n. sp. can be distinguished from other known described species by the perineal pattern of the female; by the lateral field of the males in M. deconincki and M. litoralis; by the long stylet and the more posterior position of the dorsal gland orifice in female and male of M. deconincki and by the elongated stylet knobs of the male in M. oteifae.

Horsenettle Cyst Nematode, Heterodera Virginiae N. Sp., a Parasite of Solanaceous Plants 1)

Heterodera virginiae n. sp. in eastern Virginia is described as a parasite of solanaceous plants. It is distinguished by the convex anterior face of the female dorsal stylet knob in lateral view. The turbinate to subglobose cysts have a maze-like wall pattern between the anus and fenestra.

Electron microscopical studies on Ditylenchus dipsaci (Kühn). I. Stomatal region.

The stomatal region of Ditylenchus dipsaci, approximately 15 μ long, was studied in cross-section. The cuticle consists of a thin cortex and a thick matrix whose inner layer consists of regularly arranged crystalloid structures. The head skeleton is basically a hexagonal tube with six radiating blades. The somatic musculature begins with two muscle cells in each sector. Each muscle cell consists of alternating bands of thick and thin myofilaments. Three stylet protractors are present which gradually become trifid as they extend anteriorly. They originate at the body wall and are inserted on the ridges on the surfaces of the stylet knobs. The guiding apparatus consists of a steep-sided cone and a cylindrical stalk of approximately the same length. Its anterior end is fused onto the base of the head skeleton and its posterior end fuses onto the anterior surface of the stylet knobs. The four dorsolateral and ventrolateral cephalic nerves could be traced from the level of the stylet knobs. Each of them branches twice. The two lateral cephalic nerves do not seem to conform to the same branching pattern. Cilia were observed in the amphidial pouches. The two myelin figures observed were identified as part of the amphidial nerves but there is no conclusive evidence that the cilia are their end processes.

Sphaeronema Whittoni N. Sp. (Nematoda: Criconematidae)

A new species of Sphaeronema is described. S. whittoni females are distinguished by their round stylet knobs, vulval lips flush with the body, lack of cuticular pattern, and large size. Males and second stage larvae differ from other described species in the shape of stylet knobs and body size.