The Faunal Relations of Oligoghaeta in the Nile Basin

Abstract

The Nile basin is poorly known as concerns invertebrate biology and particularly oligochaete faunal relations. What is known of these relations, however, well reflects the complex history and multiple origins of this great river. Although oligochaetes were collected from several parts of the Nile basin, many other parts were never explored for this much neglected group. Records of Egyptian oligochaetes were compiled by Khalaf&Ghabbour (1967), oligochaetes from Ethiopia, Kenya, Tanzania, Uganda and Zaire were described by Brinkhurst (1966) and Brinkhurst&Jamieson (1971). Most of the Sudan has not been well investigated, but some collections were made at points which showed clear faunal boundaries. From the available information summarized in Table 1 three major faunal divisions of the Nile basin can be recognized: a. a northern Lower Nile division from the Delta to Khartoum characterized by Alma nilotica, b. the Upper Nile division with its complex of tributaries extending to central and East Africa characterized by Alma emini, and c. the Blue Nile division including the Ethiopian highlands characterized by the absence of Alma. These divisions are so clearly defined and separated by faunal voids that they easily suggest two things (or rather reinforce suggestions from other evidence): 1. the River Nile is not of a single origin but is an ancient system of several river and lake systems which were connected and disconnected more than once, 2. that the latest connection which gave the River its present shape, the flow of the Blue Nile into Egypt, is more recent while connection of the Egyptian Nile with the White Nile system or at least a river system in northern and central Sudan, is much more ancient. This comes out from the observation that the Egyptian fauna has substantial relations with the fauna of the Sudan and the faunas of central, East, West and Southern Africa but bears very little resemblance to the fauna of the Blue Nile and Ethiopia.

Ed. Dr. Ghabbour’s contribution is printed without changes although the editor does not agree with some opinions presented. The origin of the Nile system has been discussed in ch. 1–3 and interpreted differently; many species of Oligochaeta in the Nile listed in Table I have a cosmopolitan distribution; conditions of distribution are mainly ecological and will undergo great changes esp. in the Nubian sector of the newly created lake.