Baylis, H.A., 1939. A new species of Oxyuris (Nematoda) from a rhinoceros. Annals and Magazine of Natural History (11) 3: 516-524, figs. 1-5
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| Location: |
Africa - Eastern Africa - Uganda |
| Subject: |
Diseases - Parasites |
| Species: |
African Rhino Species |
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Oxyuris karamoja. The species to be described in this paper was obtained from an African rhinoceros (Rhinoceros bicornis) in the Karamoja district of Uganda, and specimens of it were kindly forwarded to the writer by the Senior Veterinary Research Officer at Entebbe. The type-specimens will be deposited in the British Museum (Natural History).
Oxyuris karamoja, sp. n.
The material included one male and seventeen females, of various sizes and degrees of maturity. The length of the male is about 14 mm. and its maximum thickness0.8 mm. The largest female measures 68 mm in length and about 2.6 mm in maximum thickness. In the smallest female the uterus contains no fully-formed eggs, but fertilization had taken place, as shown by the presence of a mass of cement over the vulva. This specimen measures 25 mm in length and 1.13 mm in thickness. The smallest female with fully-formed eggs is just over 30 mm long and about 1.5 mm thick.
The cuticle shows coarse transverse striations throughout, the intervals between them, at about the middle of the body, reaching about 0.055 mm in the male and from 0.09 to 0.24 mm. in the females, according to their size. The cuticle near the anterior end is slightly inflated, or, rather, the subetiticular layer is separated from it by a space. The characters of the anterior extremity (figs. 1 and 2) differ somewhat from those of O. equi (fig. 3). The aperture of the mouth, instead of being hexagonal, is almost oblong, with its longer axis laterolateral. The lateral papillae (fig. 2, 1) are similar to those of O. equi (fig. 3), but their terminations are situated on the lateral borders of the mouth instead of some distance away from it. The four submedan papillae (fig. 2, s) are somewhat similar in structure to those of O. equi (fig. 3, s) and have similar branching intracuticular processes radiating from a central point, but they lack the regular peripheral circles of rod-like rays. In addition to these organs there are four internal papillae (fig. 2, p), two subdorsal and two subventral, with terminations projecting on the lining of the buccal cavity, at a deeper level than the lateral papillae. The existence of these internal papillae in O. equi does not appear to have been described, nor has the writer been able to observe them in that species.
The cuticle lining the mouth-aperture appears to be smooth. This is a further point of difference from O. equi (fig. 3), in which the cuticle bordering:tlie mouth shows a delicate network of raised ridges. This structure seems to have been observed by Fl?gel (1869), who describes it as a 'zellenartige Zeichnung,' but is more accurately described by Martini (1916). Within the aperture there are, as in O. equi, six delicate, more or less semicircular cuticular plates (two lateral, two subdorsal, and two subventral) projecting inwards from the lining of the buccal cavity. The latter has a depth of about 0.05 mm. in the female and 0.1 - 0. 15 mm in the female. In the female only there are three hook-like teeth projecting into it from its floor, which is formed by the cuticular covering of the interior end of the oesophagus. These teeth are broad and flattened when seen in frontal view (fig. 2), and curve outwards at their free extremities (fig. 1). Unlike the teeth of O. equi (fig. 3) they appear to be quite smooth and without denticulations. The cuticular bristles which, in the female of O. equi, originate at the same level as the teeth, and project into the buccal cavity, are here absent.
The oesophagus (fig. 4) is of a very characteristic shape. Its total length, measured from the anterior extremity, is 1.75 mm. in the male and about 2.5-3 mm. in the female. Its anterior portion is somewhat flask-shaped, being narrow near the mouth and expanding rather suddenly just behind the nerve-ring. This is in strong contrast to the shape of this portion of the oesophagus in O. equi, the widest portion of which is near its anterior end. This anterior portion, in O. karamoja, measures 0.85 mm. in length in the male and 1-3-1.55 mm. in the female, and attains a maximum width of 0.32 and 0.430.54 mm. respectively. It is followed by a bulb with an elongate, narrow neck. The length of the whole bulb is about the same as that of the anterior portion (0.85 mm. in the male and 1.2-1.5 mm in the female). In the male the maximum diameter of the bulb is 0.33 mm., in the female 0.44-0.6 mm. The bulb contains a valvular apparatus with a relatively thick, transversely corrugated cuticular lining. The nerve-ring surrounds the anterior portion of the oesophagus at a distance of about 0.3 mm in the male, and about 0.5 mm in the female, from the anterior extremity. The excretory pore is situated far behind the oesophageal bulb, at a distance of 4.5 mm in the male, or 7-8.5 mm in the female, from the anterior end. In the female it is about 1-5-3.5 mm in front of the vulva.
The form of the caudal end in the male (fig. 5) is similar to that of O. equi. The papillae have the same arrangement, there being one pair of preanal papillae with long, stout peduncles, and three pairs of postanal papillae.
Of these the most posterior pair are very large, with stout, conical peduncles supporting a rectangular cuticular expansion. The two smaller pairs are close to the cloacal aperture, the inner pair on a process which is grooved ventrally and forms a support for the spicule when the latter is protruded. Eblers (1899) describes and figures a median preanal papilla in O. equi. The writer has been unable to confirm the existence of this papilla in either species, or of the two other papilla-like structure figured in front of it by Ehlers, but not mentioned in his text. The anterior lip of the cloacal aperture contains a parenchymatous structure with a fringe of rays or processes on its posterior border. The spicule, in the single specimen available, measures about 0.21 mm. in length. Its extreme tip is possibly missing.
The tail of the female (fig. 6) shows a similar variation in length to that of O. equi. This variation, as in that species, is evidently correlated with the age and maturity of the specimen, the tail becoming longer as more space is occupied by the developing uterus. In the smallest female, without eggs, the anus is situated at 2.4 mm. from the posterior extremity. In other specimens the tail varies from 6 to 22 mm in length. There is no con- striction marking it off from the body, the latter beginning to taper gradually some distance in front of the anus.
The female genital organs are similar to those of O. equi. The vulva is situated at 7.5 mm. from the anterior end in the immature female, and at 9-12 mm. in older specimens. The muscular vagina runs forward at first from the vulva, then doubles back and passes into the long, straight egg-reservoir. This extends to just behind the anus in the immature worm, and to within 2-3 mm. of the tip of the tail in older females, maintaining this relationship as the tail elongates. The growth of the tail thus appears to take place between this point and the anus. The arrangement of the uterine branches and ovarian tubes is the same as in O. equi. The eggs are also similar, the shell having an operculum at one end. They measure 0.086-0.094 mm x 0.038-0.04 mm. The shell is sometimes regularly oval, sometimes more pointed at one end than at the other. In the latter case the operculum is at the broader end.
As has been shown in the foregoing description, this species differs in several respects from Oxyuris equi (syn. O. curvula), the common form occurring in Equidae, though it bears a very close superficial resemblance to it. M?nnig (1927, p. 224) has recorded the occurrence of O. equi in Rhinoceros bicornis in Zululand, but gives no description of the specimens. It seems possible that these may actually have been examples of the species here described as O. karamoja. The other species at present assigned to Oxyuris (sens. strict.) are O. tenuicauda v. Linstow 1901, from a zebra (Equus crawshayi) in East Africa and O. poculum v. Linstow, 1904, from ponies in Ceylon. It appears uncertain whether either of these is really distinct front O. equi. In O. poculum, however, the spicule of the male is said to be 0.44 mm long, and thus much longer than is usually recorded for O. equi,. The male of O. tenuicauda is unknown, and the female is very inadequately described. Oxyuris triradiata Hall, 1916, which was doubtfully referred to Oxyuris (s. s.) by Yorke and Maplestone (1926), has been shown by Manter (1930) to belong to the genus Citellina Prendel, 1928.
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A new species of Oxyuris (Nematoda) from a rhinoceros
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