Crocodile River Research Articles

Bacteriological aspects of pollution in the Jukskei — Crocodile river system in the Transvaal, South Africa

A combination of routine methods of bacteriological analysis has been utilised to investigate conditions in a river system which in part is subject to the effects of the discharge of appreciable quantities of sewage effluents which, during the dry season, may constitute the major part of the total flow. Other parts of the river system are free from gross pollution, and results obtained from these sections served as a basis for comparison. The river system is capable of coping with most of the detrimental effects of direct faecal pollution in varying form. But under no circumstances do these findings imply that the river system is capable of dealing with unrestricted quantities of sewage effluents for an unlimited period of time. Industrial pollution of varying character has been found to have little, if any, effect on bacterial numbers. The effect these effluents may have on the composition of the bacterial population as a whole has not been investigated, but this influence would be of local significance only. The methods used and the interpretations applied to the results seem to constitute a valuable instrument in the detailed study and assessment of bacteriological quality of the waters in a natural river system which is subject to severe pollution from sewage and industrial effluents of varying character.

Limnocnida rhodesiœ Boulenger, with some Remarks on the Distribution of the Genus Limnocnida.

Summary.The morphology of the freshwater medusa, Limnocnida rhodesiœ Boulenger, obtained from new sites in the Zambesi and Limpopo river‐systems, is described and illustrated by photographs (Pl. I.).The new sites for L. rhodesiœ are the Prince Edward Dam on the Hunyani River, near Salisbury, the Hartebeestpoort Dam on the Crocodile River, near Pretoria, and the Bezuidenhout Valley in Johannesburg.The range of dimensions of L. rhodesiœ is extended, the present specimens being larger than those previously described.The specimens of L. rhodesiœ examined from the new localities were all females in active egg‐production. Manubrial bud‐formation was seen in only a few specimens.A species of Trichodina occurred in small numbers on the external surface and tentacles of L. rhodesiœ from the new localities cited.Some ecological notes on Limnocnida are given.The present geographical distribution of the genus Limnocnida is discussed and the continued southward range of distribution in Africa from Lake Victoria Nyanza to Johannesburg is detailed. Similarly, the distribution of the known species of Limnocnida is given, L. tanganicœ, the Central African form, being replaced by L. rhodesiœ in Rhodesia and the Transvaal, and by L. indica in India.The possible significance of the present‐day geographical distribution of Limnocnida in relation to former geological conditions on the earth's surface is discussed.

Limnocnida rhodesiæ and its Distribution

WHILE resident in Johannesburg, South Africa, we often made inquiries regarding the possible occurrence of the interesting medusae belonging to the genus Limnocnida in the subcontinent, and searched many rivers, dams, ponds and pools for them. On personal visits to various parts of Southern Rhodesia in 1920 and 1927, unfortunately, specimens could not be obtained. However, at Hartebeestpoort Dam, on the Crocodile River, the chief tributary of the Limpopo, about 22 miles from Pretoria, Transvaal, on March 23, 1926, at the end of the summer season, one of us found three medusae, 18–20 mm. in diameter. These specimens we considered to be Limnocnida rhodesae, Boulenger.

Bilharzia Infection in South Africa

In 1916 Dr J. C. Becker made the interesting discovery of Bilharzia infection in Physopsis africana collected at Nijlstroom in the Transvaal and obtained the adult flukes in some guinea-pigs he had exposed to infection with the cercariae. The town of Nijlstroom is situated at the source of a tributary of the Limpopo river at an altitude of 3924 feet above the Indian Ocean into which it flows. In 1917 I collected2 infested examples of P. africana at Magaliesburg, a popular picnic place for Krugersdorp residents, situated on a branch of the Little Crocodile river which later joins the Limpopo. Magaliesburg has an altitude of 5000 feet above sea-level. I also obtained infested examples from Rustenburg, thus revealing a further source of infection from tributaries of the Little Crocodile river, at an altitude of over 4000 feet.

Report on the Crocodile River Iron Deposits. By P. A. Wagner. Geological Survey of the Union of South Africa, Memoir No. 17. pp. 65, with 12 plates and 5 figures. 1921.

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The Geology of the Transvaal 1

THE most interesting features of the report of the Transvaal Geological Survey for the year 1906 are the excellent pieces of detailed mapping of the rocks of the Transvaal System, in the Lydenburg district, between Lydenburg and Belvedere, by Mr. A. L. Hall, and in the area immediately east of the Crocodile River and south of the Rooiberg by Mr. W. A. Humphrey. These two districts form parts of the same great synclinal trough; but while the Lydenburg district is at the eastern end of the trough, and is as remarkable for the simplicity of its geological structure as it is famous for the grandeur of its scenery, the area mapped by Mr. Humphrey lies 200 miles to the west and nearer the centre of the trough, and is characterised by an exceptionally complicated structure. Surrounded by the much later Red Granite formation, the isolated inliers of the Transvaal System in the latter area owe their position to faulting and folding on a large scale, an adequate explanation of which can only be forthcoming when the area to the west is mapped in detail.

The Game Fields of the Eastern Transvaal2

IN proceeding into the interior of Africa from almost any point on the eastern coast, the traveller passes over a low coastal plain to the foot of the scarp of a high plateau. This plateau is succeeded to the west by a still higher one, which is gained either by a second steep ascent or by a gradual slope. The existing river valleys and former earth-movements have in places interrupted this arrangement; but, notwithstanding a few such exceptions, it persists with remarkable uniformity from Abyssinia to Natal, where the dominant meridional geographical lines bend round into the east and west series that rules in Cape Colony. In the eastern Transvaal, this zonal arrangement of the country is well developed. Inland from Delagoa Bay is a tract of undulating lowland, ending at the foot of the Libombo Mountains, which separate Swaziland and the Transvaal from Portuguese East Africa. Seventy miles further to the west is the parallel range of the Drakensberg or Kahlamba (to adopt the author's spelling of the name, which is usually written Quahlamba). Between these mountain ranges is a belt of bush-covered veldt. The Crocodile River (a tributary of the Komati) and the Olifants River flow from west to east across this belt, at a distance of about l00 miles from one another. These, with the mountains, enclose a roughly quadrangular area, some 7000 square miles in extent, which is the favourite hunting-ground of Mr. F. V. Kirby. Small though this area is, it includes very varied types of country. To the west are the densely wooded eastern slopes of the Drakensberg, and part of the turf-clad plateaus or terraces beyond; to the east lies low country with sub-tropical vegetation, intervening between the Libombo Mountains and the Limpopo River. Most of the area consists of barren, scrub-covered plains known in this part of Africa as Bush-veldt, and near the equator as the Nyika. Most of this area was once rich in game. In the Bush-veldt lived the rhinoceros and buffalo, the sable and roan antelopes, the gnu, waterbuck, zebra and mpalla. The wooded foothills of the Drakensberg, or the “Kloof Country,” was the home of the koodoo, the hill-leopard, the bush-buck, and the reed-buck. On the western plateau, or the “Krantz Country,” in addition to some of the animals mentioned, lived the oribi and the mountain reed-buck.