Studies on the extent of variation in Hoplolaimus indicus Sher, 1963 I. Morphological characters Chawla M. L., Yadav S. M. Division of Nematology, Indian Agricultural Research Institute New Delhi-12. Presented at Nematology Symposium held at Coimbatore, India in February, 1981 Abstract Most of the presently described nematode species being phenetic, availability of information on the morphological variability within any specjes is of paramount importance for authenticity in taxonomy. Therefore, all the 14 (25, including sub-categories) characters of 460 topotypes (plus 100 topotypes used for en face views) were studied and observations recorded. An additional numbet (560) of specimens collected from four different hosts (sugarcane, sorghum, citrus and banana) each from four localities (Hissar Narnaul, Udaipur and Delhi) was also studied. These too, were found to fall within the range of morpholo gical variations of topotypes. The variations are as ander:
Body shape: The body was generally stightly to more ventrally curved but many other (open C, closed C, Jay, hook, open spiral and even closed spiral) curvatures also appeared. Lip region: The lip region varied in shape; sclerotization (very light to heavy); demarcation (rarely continuous to generally distinctly set-off) number of annules on head (smooth to 5 or 6 annules); furcation of radial arms of cephalic sclerotization (bi, tri or tetrafurcate dorsal and ventral arms and (2 to 21 lobed en-face view depending on the same number of longitudinal striations on basal annule. Cephalids: The anterior and posterior cephalids may be located 2–4 annules behind head and conus-shaft junction of spear in few cases (normal position is 0–1 annule behind head and in level with conus-shaft juction respectively). Lateral field: Lateral field with none to 1, 2, 3 or 4 incomplete, small and superficial incisures not visible as grooves in transverse body sections; or generally only as breaks in tranverse striations of totomounts. Phasmids: Phasmids 2-5um in diameter, anterior 23–46% while posterior 65–95%, either of them may be right or left; double anterior and/or posterior phasrnids were also observed in 3 specimens. Two specimens revealed 5 phasmids each. Excretory pore: Excretory pore may by located any where from in level with anterior end of the valves of median bulb to about a body width posterior to oesophago-intestinal valve. Two excretory pores with distinct ducts were seen in a specimen. Hemizonid and hemizonion: Hemizonid differed in location from at level with excretory pore to 26 annules behind it. A specimen had second hemizonid 25 annules above excretory pore. Hemizonions may be more than 1 (upto 3), located one to 35 annules behind hemizonid. Spear: Spear knobs may have 1, 2 or 3 anterior projections and thus with irregular anterior surfaces. Oesophagus: Oesophagus with 4 dorsal gland nuclei and 1 subventral in same plane, the 6th-that of the other subventral in slightly different plane-total 6 nuclei. Coefficient of gland overlap = 24–76%. Median bulb generally round, well set-off, may sometimes become slightly to more ovoid, not well set-off from procorpus. Rectal overlap of intestine: In most of the topotypes, an extension of the intestine went beyond the recto-intestinal function but the length of this post-rectal overlap varied from a condition hard to interpret between “present or absent” to the one where almost entire tail was occupied by intestinal extension. Spermatheca: In many specimens the spermatheca was not visible but in some it was very distinct (perfectly spherical to ovoid). The frequency of success for locating spermatheca differed from population to population. Generally speaking, it was more where males were more abundant. Tail: Both the shape and the number of annules varied considerably. The tail shape varied lesser within males but in females it departed in 15% of the specimens from the normal rounded shape showing that the departures from the typical shape were not rare. Such variations could broadly be classified as:
narrowing towards tip, dorsally, convex, ventrally flattened, dorsally flattish but ventrally convex, notched dorsally, superficially moderately, deeply or very deeply, notched ventrally superficially, moderately, deeply or very deeply, and notched terminally superficially, moderately, deeply or very deeply.
The number of tail annules langed from 7 to 22 and the annulation always extended upto its tip. However, the distinctness of caudal annulation varied considerably, becoming inconspicuous in occasional specimens. In some of the specimens some of the annules in region of the tail tip had almost double the width of adjacent annules number of annules countable on dorsal side was not necessarily equal to those on the ventral side. Counting of tip annules was sometimes difficult due to fusion of annules and/or notching of the tail. Caudalids: Caudalids (not seen by Sher) differed in position from 10 annules anterior to anus to 9 annules posterior to anus. Epiptygma: Epiptygma may be completely absent; single anterior/posterior or double (anterior and posterior).
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