SOME PAKASITIC ROUND WORMS OF THE RABBITWITH DESCRIPTIONS OF TWO NEW SPECIES.
By Asa C. Chandler,Of the Biological Laboratory, Rice Institute, Houston, Texas.
In the course of parasitological examinations of domestic rabbitskept in the animal house of the Rice Institute biological laboratory,it was found that nearly every specimen was infested by trichostrongy-lid worms, and in some instances three different species were presentin considerable numbers at the same time. The fact that immaturespecimens of all three species were present in some of the rabbitsAvhich had been kept in the animal house for from six weeks to twomonths, would seem to indicate that the infection, in some instancesat least, was acquired in the animal house. Since all of the rabbitswhich have been kept in the house have been obtained in Texas, frombreeders either in Houston or New Braunfels, it is probable that theworms originally came from Texas.One of the species, and the one found in greatest abundance and inthe largest number of individuals, is Trichostrongylus calcaratus.described by Ransom (1911) from cotton-tail rabbits, Sylvilagiisiloridanus maUums, in Maryland. A number of young individualsof this species were found. The males, up to a length of about 3 to3.5 mm., have the posterior end of the body terminated in a bulbwith a conspicuous spine on the postero-dorsal extremity of it (fig.1 ) . Within the bulb the bursa of the adult develops, the body thendrawing away somewhat from the larval cuticle, as shown in thefigure. No doubt the final moult takes place shortly after this.NEMATODIRUS LEPORIS, new species.Plate 1, figs. 2-5.Specific diagnosis. Long slender worms of small size, blood redwhen freshly removed. Inflated cuticle of neck asymmetrical, andconspicuously striated.Male 8 to 13 mm. long with a maximum diameter of from 95 to135 [x. Esophagus 400 to 500 ^ in length. Bursa (fig. 3) well ex-panded, its breadth (250 [;.), greater than its length (210 [x), anNo. 2553.?Proceedings U. S. National Museum, Vol. 66, Art. 1680092?24 1
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unusual condition in the genus. Dorsal lobes of bursa set otf fromlatei'al lobes by a distinct notch and separated from each other by ashallow indentation. Dorsal ray moderately stout, bifurcated toabout one-fourth its length from the tij) of the longest prong. Ex-terno-dorsal rays long and ver}^ slender, about midway betweendorsal ray and postero-lateral ray. Postero-lateral and medio-lateralrays close together, arising from a common trunk, and extendingalmost to the margin of the bursa. Externo-lateral ray stout, cui*v-ing sharply away from other lateral rays in its distal third, andending at some distance from the bursal margin. Latero-ventraland vent ro-ventral rays in contact for their whole length, curved for-ward, and ending at some distance from the bursal margin. Theserays are much more slender than the lateral rays, but mucli thickerthan the doreal ray. Their length is only about half that of theexterno-lateral and medio-lateral pair. Bosses numerous and small,occupying the portion of the bursa from near the ventral marginto the externo-lateral and medio-lateral pair of rays. Spicules (figs.4^5) deep brownish red in color, 0.65 to 1.05 mm. long, united forthe greater part of their length, and showing distinct striations onthe proximal half. Tip of spicule curved ventrally, and ending ina membranous bulb. A pair of membranous wing-like expansionsoccur along the ventral side distally, ending in obtuse angles justproximal to the bulb. These membranous expansions have very finemarkings as shoAvn in figure 5. The body of the spicule ends in afinger-like process bent sharply dorsal, and ending on the dorsalmargin of the bulb.Female 16.5 to 20 mm. in length, with a maximum diameter of180 to 220 [L at the vulva. Diameter abruptly but moderately reducedbehind vulva. Head diameter 35 to 40 [a, exclusive of inflated cuticle
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latter well developed, usually markedly asymmetrical, conspicuouslystriated, reaching a diameter of from 55 to 75 \i. and extending backon the neck to a point 130 to 145 jx from the anterior end. Esophagus450 to 600 [JL in length. Tip of tail truncated and provided with theusual bristle-like process. Anus 105 to 115 [i from truncated end ofbody. Vulva a transveree slit 420 to 486 pi, almost exactly one-fourthlength of body, from posterior end. Eggs long oval, measuring 160to 180 PL by 80 to 90 pi, in various stages of development from morulato fully formed eml)rY() when deposited.Host.?Domestic rabbit, Oryctolagus cuniculus.Location.?Duodenum.Locality.?Houston, Texas.Type.?Male, U.S.N.M., Helm. Coll. 7733; paratypes, males andfemales, U.S.N.M., Helm. Coll. 7734.This species of Nematodirvs seems to come closest to flicoUis,which it resembles in general bursal characteristics, short spicules.
ABT. 10. PARASITIC BOUND WORMS OF THE RABBIT?CHANDLER. 3and position of vulva, and distinctly falls into the filicoUis group asdescribed by May (1920). The male differs, however, in the form ofthe tip of the spicules, in the shape of the bursa, in details of thearrangement and relative size of the bursal rays, in the number andarrangement of bosses, and in the thickness of the body. The femalediffers in its more slender body, the greater length of the tail, and inthe more posterior position of the vulva. The latter characteristic issufficient to distinguish the females from any other species of thegenus. In this respect it approaches the genus Mecistocimts, butdoes not approach it at all, as do some other species, in length ofspicules, size of eggs, or presence of cervical papillae. This stillfurther bears out May's (1920) contention that Mecistocii'^i'its is notjustifiably separated from Nematodiru^.OBELISCUS CUNICULI GraybiU (1923).Plate 2, figs. 6-11.Since tlie original draft of this paper was written, the descriptionof this worm by GraybiU (1923), as a new genus and species, hasappeared. It seems desirable, however, to add a few details toGraybilFs description.The worms are relatively large and robust for Trichostrongylids.GraybiU describes them as whitish in color with some dark streakingdue to the color of the intestine, but when living, in a freshlj'opened stomach, the worms are blood red in color. The long-itudinalcuticular ridges vary in number from 16 to 26 in males and from 36to 40 in females. These ridges are broken by transverse indentationsat intervals of about 200 |x in the anterior portion of the female, andat somewhat shorter and more irregular inteiwals in the male. Ex-tremely fine and inconspicuous transverse striations are present,most evident in the region of the vulva and on the tail of the female.The nerve ring crosses the esophagus a little anterior to the middleof it-s length.The bursa (fig. 7), as mentioned by GraybiU, consists of two largerounded lateral lobes, separated from each other dorsally by arelatively small dorsal lobe. At the obtuse angles fonned wherethe ventral rays on the one hand, and the medio and postero lateralrays on the other, terminate near their margins, the bursal lobeshave a maximum width of about 400 to 450 pi, while their maximumlength, measured to the point where the extemo-lateral ray ter-minates, is about 500 to 600 [jl. The entire ventral surface of the1)ursa, except a fluted margin about 40 [x in width, is thickly coveredwith dew-drop-like bosses, giving the bursa a beautifulh^ sculpturedappearance. The ventro-ventral ray is smaller than any of theother rajs in the lateral lobes except the externo-dorsal. The latero-
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ventral ray is the largest of all. It is very stout basally and runsnearly parallel with the externo-lateral for about half its length,being widely separated from the ventro-ventral. The distal half,which tapers markedly, performs a wide sweeping curve forwarduntil it comes very near to the ventro-ventral at the iimer limit ofthe fluted bursal margin. At this point it bends outward again,so that the tips of the two ventral rays come to lie parallel in thefluted margin of the bui^a, in an obtuse angle formed in the bursaat this point, directly opposite a similar obtuse angle formed wherethe medio- and postero-lateral rays terminate. These latter tworays are of moderate size, approximately equal, parallel, and curvingdorsally. The externo-lateral ray is much larger than the otherlateral rays, curves toward the ventral rays, and terminates in asharply constricted finger-like tip at a point on the margin of thebursa about midway between the ventral and the other lateral rays.The small but stout externo-dorsal ray curves dorsally and ter-minates in the margin of the bursa about midway between the tipsof the postero and medio-lateral rays and the junction of dorsal andlateral lobes.The small dorsal lobe (fig. 8) is of very peculiar structure. Itis overlapped, as Graybill has pointed out, by the lateral lobes, andis sharply marked off' from them. It is supported by a single dorsalray which forks distally into two bifurcated tips. Near the middleof its length a pair of branches are given off' which curve ven-trally, pass through a minute foramen, and enter a vesicular swell-ing as in Cooperia. Ventral to this swelling there is an additionalmembranous flap, supported by a pair of very minute, delicate par-allel rays.In some of the specimens measured the spicules (figs. 9-10) areconsiderably larger than those measured by Graybill, a number ofthem varying between 500 and 540 ]x in length with a lateral diame-ter of 50 ^. Although the chitinous portion of the spicules iscleft distally, and terminates in a dorsal and a ventral hook, thespicules can not be said to be cleft, since these parts are connectedby a membrane as shown in figures 9 and 10. The ventral hookis the larger and coarser, bending in a medioventral direction; thedorsal hook bends dorsally, laterally, and then distally, ending in aslender point. The membranous expansions at the distal ends of thespicules extend beyond the chitinous hooks.A few of the females reach a length of 20 mm. Graybill givesthe maximum length as 18.5 mm. He records the maximum widthof one specimen as 546 p., but in the Texas specimens the greatestwidth, of about a dozen specimens measured, was 400 [a, just an-terior to the vulva. At this point there is a marked reduction in
ART. 16. PARASITIC ROUND WORMS OF THE RABBIT CHANDLER. 5diameter to from 305 to 340 [x. The diameter of the head anteriorlyis only 80 [x, but 110 [j. from the anterior end it has widened out to150 [X. Graybill gives the diameter of the head as 119 ^. The vulva,guarded by a pair of inconspicuous lips, is situated about one-fifththe length of the body (3.6 to 4.5 mm.) from the posterior end, itslocation being readily recognized by the abrupt diminution in diame-ter of the body and the angular bending of the body at this point.The vagina is very short, joining the divergent ovijectors almost im-mediately. The muscular portions of the ovijectors can hold four orfive eggs apiece ; there is no well-marked sphincter between the mus-cular and nonmuscular portions, but a very strong sphincter sepa-rates the nonmuscular portion from the uterus. The terminal por-tion of the uterus is also muscular, and can contract so that only oneegg at a time can reach the sphincter. The eggs in the Texas speci-mens measure 80 to 92 [x by 56 to 64 [x, whereas Graybill recordsmeasurements of 76 to 86 [x by 44 to 45 [>. in the New Jersey speci-mens.^In spite of a number of slight discrepancies in the descriptionsand measurements of the Texas and New Jersey si^ecimens, it isvery unlikely that more than one species is represented. My meas-urements were made from living narcotized worms, whereas Gray-bill's may have been made from preserved and prepared specimens,'which would account for some of the differences.When present in considerable numbers this worm produces a verymarked erosion and ulceration of the stomach wall. The worms arefound adhering firmly to the mucous membranes, and in some in-stances seem to have their heads buried deeply in the wall. Inmost of the rabbits examined only from one to five or six wormswere found, but in one specimen about 50 adult worms and a numberof immature specimens were found. Part of the material describedabove has been deposited in the Helminthological Collections of theU. S. National Museum, Nos. 7735 and 7736.LITERATURE CITED.Graybill, H. W. :1923. A New Genus of Nematodes from the Domestic Rabbit. Parasit.,vol. 15, pp. 340-342. pi. 11.May, H. G. :1920. Observations on the Nematode genus Nematodirus with Descrip-tions of new Species. Proc. U. S. Nat. Mus., vol. 58, pp. 577-588,pis. 29-35Ransom, B. H. :1911. Two New Species of Parasitic Nematodes. Proc. U. S. Nat. Mus.,vol. 41. pp. 363-369
6 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.66.EXPLANATIONS OF PLATES.
???anus. n. m. ovij.?uon-iuuscular portion ofa. d. 1.?accessory dorsal lobe. ovijector.a. d. V.?accessory dorsal raj'. oe.?esophagus.a. ov.?ascending oviduct. p. I.?postero-lateral ray.d.?dorsal ray. s.?sphincter of ovijector.(I. li.?dorsal hook. ;/.?uteinis.d. Z.?dorsal lobe. v.?vulva.d. v.?ventral branch of dorsal ray. va.?vagina.e. d.?externo-dorsal ray. v. h.?ventral hook.e. I.?externo-lateral ray. v. 1.?ventral lobe.I. V.?latero-ventral ray. *. v.?vesicular swelling under dorsal
??'. I.?medio-lateral ray. lobe.m. ovij.?muscular portion of ovi- v. i\?ventro-ventral rjiy.jector. Plate LFig. 1.
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Trklwstrongylus calcaratus. Posterior end of young male, shoM'ingbulb-like expan.sion of larval cuticle, with developing bursainside.2-5. yemaiodirus leporis, new species. 2, adult worms, entire. 3, bursa,from left side. 4. spiciiles, entire, from left side. 5, tip ofspicules, from left side.Plate 2,Figs. 6-11.
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Obeliscus cunicuU. 6, adult worms, entire. 7, bursa, dorsal view.8, dorsal lobe and accessory parts, from ventral side. 9, spicule,entire, lateral view. 10, Distal portion of spicule, dorsal view,slightly medial. 11, A'ulval region of female, showing ovijectors.o
U. S. NATIONAL MUSEUM PROCEEDINGS, VOL. 66, ART. 16 PL. I
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0.2 mm.Trichostrongylus calcaratus and Nematodirus leporisFor explanation of plate see page 6
U. S. NATIONAL MUSEUM PROCEEDINGS. VOL 66, ART. 16 PL. 2
looyu. Obeliscus cuniculiFor explanation of plate see page