Transactions of the Royal Society of Tropical Medicine and Hygiene/Volume 1/Physaloptera Mordens: A New Intestinal Parasite of Man
PHYSALOPTERA MORDENS: A NEW INTESTINAL
PARASITE OF MAN.
By ROBERT T. LEIPER, M.B., F.Z.S.
Helminthologist to the London School of Tropical Medicine.
(Friday, December 20th, 1907.)
During a recent visit to Uganda, for the purpose of making a reference collection of the helminthic parasites of that country for the Museum of the London School of Tropical Medicine, I had the opportunity of investigating in the Research Laboratory at Entebbe a curious "ascarid"-like nematode that ha,d been obtained at a postmortem of a native who had died, in the hospital, of sleeping sickness. From my examination of the material, which had been very kindly placed at my disposal by Dr. Gray of the Royal Society Sleeping Sickness Commission, I was able to determine that the specimens belonged to the genus Physaloptera, a genus that had hitherto been found but once in man. It was not possible at the time to say, however, whether the specimens represented a new species or belonged to that founded by v. Linstow in 1902 for those discovered in Southern Russia, and named by him Physaloptera caucasica. Since my return to London I have been able to compare the details of organisation of the African form with those given by v. Linstow for P. caucasica, and with the other forms that appear in literature, and to .satisfy myself that the form met with in Central Africa presents several notable distinguishing characteristics.
The genus Physaloptera has representatives in the four higher groups of the Vertebrata, but has not yet been found to occur in fishes. There are in all fifty-five known species, of which twenty-two occur in the Mammalia.
The genus is, however, a very old one, and contains a number of species that depart very widely from the type as defined by the type-species P. clausa. Further, the characters by which many of the species in the genus have been defined are really of generic value, so that, in the absence of the original material, there is little beyond a measurement or two upon which the specificity of several species remains. This is unfortunately true of the description of Physaloptera caucasica with which the present species required to be most carefully compared.
The generic characters that appear to be constant for the species of the genus Physaloptera s. str. may be summarised as follows:—
The general form resembles markedly that of the genus Ascaris, but in the male the cuticle at the posterior end of the body is flattened out to form a somewhat heart-shaped "bursa." In both sexes the cuticle overreaches the mouth structures, forming a sort of cuticular sleeve or collar; it is, moreover, unmarked by the regular transverse striations seen in other forms, although, of course, in contracted specimens, certain transverse groovings appear adventitiously.
The mouth is surrounded by two large fleshy lips, situated laterally. Each lip bears two large submedian flattened papillae, and is surmounted by a cuticular prong called the external tooth. Beneath this, in the surface in contact with the opposing lip, is a cuticular fold that shows varying form with the different species, and is known as the inner tooth.
The bursa in the male presents a series of papillae which fall into two classes, pedunculated and sessile. Typically, there are in each species ten pairs, four pedunculated and six sessile. The pedunculated series lies in a longitudinal row, outside the sessile papillae. Though the number appears to be constant for most, at any rate, of the species, the relative position of the papillae to one another seems to be of specific value.
The vulva is situated in the anterior half of the body, and the ova show an exceedingly thick smooth shell, that in itself is highly characteristic.
The species obtained in Uganda and which we shall call P. mordens, like P. cawcasica presents all the characters above defined, as those of the genus in a restricted sense. Its size is very considerable, the male measuring 30 to 50 mm., the female 40 to 55 mm. In shape and general appearance it resembles an immature Ascaris lumbricoides—so much so as to lead me to conclude that it may have been frequently overlooked as such in the past, just as Ascaris mystax and Ascaris marginata have been. To the latter, also, it" bears a striking resemblance, the bursal expansion at the tail of the male resembling the cuticular alae that are present at the head of these two species.
The breadth of the worm is considerable, and varies from two to three millimetres. The body tapers very gradually anteriorly, and ends truncately; posteriorly it tapers rapidly in the female to a sharp tip, lying more in line with the ventral than the dorsal surface, and giving therefore the posterior portion of the worm a somewhat rounded appearance on the whole. In neither sex does the cuticle form posteriorly a preputial fold around the posterior portion of the body, as it does in some species in addition to the characteristic anterior bulging seen in all. The cuticle shows adventitious groovings that have no constant relation to one another. In this species, however, it is not absolutely without structure, exceedingly fine radiate striae being noticeable. The mouth parts exhibit several interesting details of structure that are unfortunately unnoted either in the description or in the figure of the corresponding species P. caucasica. The two large fleshy lips of P. mordens bear in addition to the pair of touch papillae and the horny "external tooth" common to these forms, a pair of cuticular knobs that jut out and lie in apposition to one another at the outer and posterior limits of the transverse fissure of the mouth, on either side (Fig. 2).
Further, the cuticular fold known as the "inner tooth," lying in the median line on the inner aspect of the lip and overhung by the horny external tooth, presents a sharp-cutting edge towards the lumen of the mouth, and projects forwards, tapering to end anteriorly in a single lancet-like tip.
Both lips are bound together posteriorly by a thick encircling cuticular band, where the cuticle leaves the surface of the anterior part of the body to form the praeputial-like fold characteristic of the genus. At a distance equal to three times the transverse diameter of this band, measuring backwards therefrom, are to be found the cervical papillae.
The alimentary canal shows the usual divisions into oesophagus, intestine, and rectum. The oesophagus, in the specimen figured, measured exactly one-sixth of the body length. It shows transverse muscular striations, and becomes only very gradually more broadened towards its intestinal opening. The chyle intestine commences with a lumen only slightly greater than the external circumference of the terminal part of the oesophagus and gradually becomes narrowed during its whole course to the short rectum, at its junction with which one finds the large unicellular masses that have been noted at this situation in many other groups of nematodes (Fig. 1).
The anus lies on the ventral surface at a distance of one-eleventh of the body length, in the male, from the tip of the tail.
The bursa in the male is oval in outline, tapering posteriorly. The papillae are in number and in general disposition according to the type of the genus, but in minuter detail of the relation of the individual papillae to one another the following points are to be noted. The external series of four pairs of pedunculated papillae do not lie in one straight longitudinal series, but are disposed so that the first and fourth pairs lie considerably within the middle, i.e. second and third, pairs (Fig. 4).
Of the sessile series of papillae the only point to note is that, in contrast with the arrangement described and figured for P. caucasica, the most anterior of the three hindermost pairs of sessile papillae on the tail are much more widely separate from one another than are the members of the two succeeding pairs.
As in P. caucasica and many other species, the ventral surface of the bursa has a peculiar "rough-shod" marking of the cuticle that lies between the most anterior pair of papillae and the second pair from the posterior end, the cuticular markings extending between this second last pair and gradually disappearing, doing so more quickly from the sides than in the centre line.
The male genital system consists of three distinctly-defined portions of the long single genital tube and a pair of very unequal spicules. The genital tube lies almost entirely on the ventral aspect of the body cavity, keeping the alimentary canal, in its whole length, on its dorsal aspect. The ejaculatory duct, the most terminal part, measures about one-fourteenth of the body length and shows well-developed musculature in its walls. The portion immediately succeeding, viz., the vesicula seminalis, is a wide and lengthened tube having a peculiarly reticulated wall, and extending forwards without kink or coil for a distance 
PHYSALOPTERA MORDENS, N.SP.
EXPLANATION OF PLATE.
Fig. 1.—Camera-lucida Drawing of an adult male Physaloptera mordens.
Fig. 2.—Mouth parts of P. mordens.
Fig. 3.—Ova of P. caucasica (a) and P. mordens (b), of the same magnification.
Fig. 4.—Ventral aspect of posterior extremity of a male P. mordens, showing the arrangement of the papillæ.
Explanation of Lettering in the Figures.
c.—Cuticular ring embracing the two lips posteriorly.
c. b.—Cuticular bosses guarding the mouth laterally.
ch. i—Chyle intestine.
B.—Bursa.
ej. d.—Ejaculatory duct.
e. d.— External tooth.
i. d.—Internal tooth.
ped. p.—Pedunculated papillæ.
ses. p.—Sessile papillæ.
sm. p.—Submedian papillæ.
sp. 1.—Long spicule.
sp. 2.—Short spicule.
t. c.—Testicle coils.
ves. sem.—Vesicula seminalis.
equivalent to about a fourth of the entire body length. Beyond the anterior limit of the vesicula seminalis the testicular tubule continues forwards with two or three longitudinal, but practically no obvious, lateral folds to within a distance (about equal to the length of the ejaculatory duct) of the oesophagus where it returns upon itself, the tine terminal part of the testicular tubule being found at about the centre of the body. The spicules are very unequal, the larger and more slender measuring 4.6 mm., the shorter and stouter 6 mm. In the female, the detailed arrangement of the two uterine tubules is not so easy to be followed, owing to dilatation of these organs with ripe ova. It can be seen, however, that the common conducting tube formed by the union of the two tubules opens by a transverse slit on the ventral surface of the body in the region between the juncture of the anterior fifth and the anterior fourth of the body length with the remaining portion.
The ovarian portions of these tubules are found greatly coiled with one another at the posterior part of the body cavity just in front of the rectum; the actual ends of the tubules are seen to be somewhat dilated and club-shaped.
The mature eggs have a thick smooth cuticular shell, and are much smaller than those of P. caucasica. They measure .043-6 by .035-3 mm. (Fig. 3).
The characters upon which the specific identity of the species may be established are: The large size of the adults; the peculiar construction of the lips and the simple formation of the inner tooth, the anterior edge of which is undivided. In the male, the disposition of the papillae; the internal arrangement of the testicular coils; the size of the spicules. In the female, the size of the ova, the position of the vulvar aperture, and the sharpened posterior extremity of the body. As already stated, the characters given for P. caucasica are few in number. The description of the mouth parts contains only facts of generic importance. Its small size, the different relation of its papillae to one another, and the difference in size of its spicules and ova will suffice to distinguish it from P. viordens.
The type-specimens are deposited in the Helminthological Museum Collection (Human Series, No. 30) of the London School of Tropical Medicine.