Chiloplacus saccatus, A..L O O F, 1971

P. A. A. LOOF, 1971, FREELIVING AND PLANT PARASITIC NEMATODES FROM SPITZBERGEN, COLLECTED BY MR. H. VAN ROSSEN, Mededelingen Landbouwhogeschool Wageningen 71, pp. 1-86 : 23-26

Chiloplacus saccatus n.sp.

( Fig. 3 , A -C).

Syn. C.quadricarinatus apud van Rossen & Loof, 1962;

Nee C.quadricarinatus ( Thorne, 1925) Thorne, 1937 ;

C.quadricarinatus apud Loof, 1964.

Dimensions:

Females (n = 34): L = 0.56 -0.83 mm; a = 20-28; b = 3.5 -4.4; c = 16-20; V = 64- 68; G prevulvar = 13-20; G postvulvar = 13 -22; G2 = 8 -13.

Female, holotype: L = 0.74 mm; a = 22; b = 4.1; c = 20; V = 67; G prevulvar = 16; G postvulvar = 17; G2 = 11.

Male not found.

Body almost straight in death except for a slight bend ventrad in the vulvar region. Cuticular annulation distinct, 2.4 \x in mid-body, 2 \i in anterior part of neck. Lateral field with four wings (five longitudinal grooves). Prelabial probolae bifurcate over one-third of their length. Edges oflips somewhat sclerotized, but true labial probolae appear not to be present. Corpus of oesophagus cylindrical, 3.4-4.4 x as long as isthmus. Nerve ring surrounding the corpus-isthmus junction. Deirids conspicuous, located at 75 -83 % of neck length from the head end, always posterior to the corpus-isthmus junction. Isthmus slender, 29 -35 \i long. Terminal bulb measuring 17 -21 X 13 -16 JJL, with valves. Hemizonid two annules long, opposite or slightly behind corpus-isthmus junction. Excretory pore immediately anterior to hemizonid.

Vulva with protruding, large, asymmetricallips.Gonadcephaloboid,inmost specimens with double postvulvar flexure. No sperm.Rudimentofsecondgonad large, 69 -87 (x or 30-45 % of vulva-anus distance. Tail sub-cylindroid with broadly rounded or somewhat truncate terminus which usuallyisindentedin the middle. Number of tail annules 14-18. Taillength 1. 9-2.6 analbodywidths. The phasmids open at 52- 69% of tail length.

Holotype: Female on slide WT 1180 . Paratypes: 27 females (two with end-on view of head) on slides WT 1181-1196; six females deposited with Dr.Morgan Golden, Beltsville, Maryland, U. S.A.

Type habitat and locality: Sample 70. This species is very widespread on Spitzbergen; it was found also in samples 1, 2, 3, 4, 5, 6, 8, 17, 18, 19,23,30, 37, 60, 62, 66 and 67.

Discussion.- Thorne (1925) described, among several Chiloplacus(Acrobeles) species, one with five lateral lines, viz. C. quadricarinatus . Since then repeatedly Chiloplacus specimens with five lateral lines have been found,andidentifiedon the basis of this character as C. quadricarinatus (van Rossen & Loof, 1962; Loof, 1964). Critical evaluation has now shown thatthesespecimensarenotall conspecific.

Twelve females of C. quadricarinatus from Thome's collection were available, collected May, 1933 from shadscale soil, Mosida, Utah, U.S.A. (topotypes)and July, 1925 from dead alfalfa, Fort Collins, Colorado, U.S.A. (types?). Dimensions: L = 0.94- 1. 16 mm; a = 19-28; b = 3.2-4.3; c = 17- 22; V = 6 3- 68; G prevulvar = 12 -19; G postvulvar = 14-22; G2 = 3- 5; T/ABW = 1.5-2.4. The deirids lie at 5 3- 72% of neck length from head end,alwaysdistinctly anterior to the corpus-isthmusjunction (in mostspecimenstheoesophagus is coiled, index 'b' corrected to length of outstretched oesophagus).Hemizonid far anterior to corpus-isthmus junction, two annuleslong.Excretoryporeopens through anterior hemizonid annule or immediately anteriortohemizonid.The corpus is five to six times as long as the isthmus. Length ofisthmus= 32- 36 \ L. The body is contracted ventrally behind the vulva. Vulvalipslargeandprotruding, the posterior one rounded, with cuticle not thickerthanon adjacent parts of body. The double postvulvar flexurein the gonad ismostlyabsent.Tail tapering, somewhat convex-conoid, terminusmoreroundedthaninC. saccatus . Tail annules 16-18. The rudimentary second gonad measuresabout40- 50ji (See Fig. 3 , H -I).

C. quadricarinatus apud van Rossen & Loof(1962) is identical with C.saccatus : the deirids lie behind the corpus-isthmusjunctionandtherudimentarysecond gonad is very long (87 [x or 33 % of the vulva-anus distance).

C. quadricarinatus apud Loof (1964) from Venezuela differs from both C. quadricarinatus of Thorne and C.saccatus by the smaller andslendererbody; by the shape of the vulva lips, by the lowerand morerounded edgesofthelips,the more truncate tail, and in that males are numerous.( Fig. 3 ,D - E).Thedeirids lie at 63 - 77 % of neck length from the head end,anteriortothecorpus-isthmus junction. The corpus is six to seven times as long asthe isthmus.Therudimentary second gonad, visible in only one female, is very short,lessthanonebodywidth and measuring 9 % of vulva-anus distance. The vulva does not protrude, the vulva lips are more symmetrical and the vagina is curved; the body is not contracted behind the vulva. This all might suggest specific distinctness from C. quadricarinatus . However, in a population from Nigeria I found most of the females agreeing in vulvar characters with those from Venezuela, but a few had protruding vulva lips agreeing in every detail with those of quadricarinatus . Males from Nigeria agreed wholly to those from Venezuela in shape and size of spicules and gubernaculum and distribution of papillae. The protrusion of the vulva lips and the contraction of the body behind the vulva may depend on the age of the individual (cf. Anderson, 1968) so this is not a reliable character. As the Venezuelan material generally is not in too good a condition, I hesitate to consider the small difference in lip shape as decisive; also there are no data upon variation in length of the second rudimentary gonad. Remains only the absence of males in Thome's populations. This, too, does not appear decisive. So I regard the populations from Venezuela and Nigeria as the true quadricarinatus . It is conceivable that during development of the adult female the shape of the tail is modified by the thickening of the body (cf. Pratylenchus neglectus, Loof, 1960 ).

Van Rossen & Loof (1962) remarked that their specimens of 'quadricarinatus' from Sweden showed several characters reminiscent of C. contractus (Thorne, 1925) and it seemed worth while to examine this species too. Ten females were available, on the same slides and from the same localities as the quadricarinatus specimens, from Thome's collection. Dimensions: L = 0.72 - 0.88 mm; a = 14-22; b = 4.2-4.9; c = 16-21; V = 66 - 68; G prevulvar = 17 -31; G postvulvar = 11-21; G2 = 4- 7; T/ABW = 1.4-1.9. In general body shape and through the distinctly protruding and large vulva lips this species strongly resembles C. quadricarinatus , from which it can be distinguished by the narrower lateral field with three longitudinal lines; smaller body; much shorter oesophagus, the index'b' being even higher than in C.quadricarinatus despite the lesser body length; less convex tail; presence of a double flexure in the postvulvar part of the gonad; and by the less regularly rounded posterior vulva lip, the cuticle of which is much thicker than that of the adjacent body ( Fig. 3 , F -G). Hemizonid and excretory pore near corpus-isthmus junction. Deirids not visible because the specimens are strongly flattened. Dimensions of three intra-uterine eggs: 61- 67 x 30- 36 fi.

Commonly C. contractus is regarded a junior synonym of C.propinquus (de Man, 1921) Thorne, 1937 , but the description of this species is insufficient and the drawing of the vulva indicates that it is not identical with C. contractus . It is best regarded species inquirenda. Acrobeles bonus Kirjanova, 1951 , synonymized with C.propinquus and C. contractus by Meyl (1961) is different from the latter as testified by the shape of the vulva.

Figures

FIG. 3. A-C: Chiloplacus saccatus n.sp., female. A: neck region; B. gonad; C: tail.D-E:. C quadricarinatus (Thorne) from Venezuela,female: D: vulva; E: tail F-G: C.contractus (Thorne), female topotypes.F: vulva;G: tail; H-J: C.quadricarinatus(Thome),femaletopotypes. H: vulva; J: tail.