99 No Doubt Prof. Tembrock Has Provided Us with a Goldmine Of

BOOKREVIEWS 99 No doubt Prof. Tembrock has provided us with a goldmine of information (take the first volume, which is devoted entirely to the Invertebrates!), which is so extensive, that I find it impossible to evaluate the work in more detail. I may add, however, that wherever I sampled the text, I found that in spite of its encyclopedic nature, it makes pleasant reading and stimulates the "curious naturalist" in us. P. SEVENSTER, Divisionof Ethology,Zoölogisch Laboratorium, Universityof Leiden, P. O. Box 9516, 2300 RA Leiden, The Netherlands. TILAPIINE FISHES OF THE GENERA SAROTHERODON, OREOCHROMIS AND DANAKILIA by ETHELWYNNTREWAVAS, 1983. British Museum (Natural History), London, England. VII + 583 pp. £50.00 hardbound. When the career of Dr. TREWAVASstarted, REGAN(1920) had only just divided the Cichlidae in a Haplochromisand a Tilapia group on the basis of the structure of the neurocranial apophysis for the articulation of the upper pharyngeal jaws. More than half a century later this same character, the phylogenetic value of which was disputed by GREENWOOD(1978), is used by TREWAVASto tentatively define within the Cichlidae a tribe of Tilapiini. Although the limits of this tribe are said to be difficult to recognize, ten genera are at present included. The relationships of three of these: Tilapia, Sarotherodonand Oreochromis(generally known as "the tilapias") are dealt with in the first chapters. Shared characters are analysed for their phyletic significance but a con- clusion on the status of the group within the Tilapiini is not reached. Differences between the genera, including methods of reproduction, food and trophic adaptations, other structural characters and biogeography are extensively treated. The still con- troversial ranking of Sarotherodon,Oreochromis and Tilapia as distinct genera, introduced only recently in an addendum to TREWAVAS(1982), is explained by the suggestion that the two mouthbrooding genera may have evolved independently from different substrate-brooding ancestors. Oreochromisis distinguished from Sarotherodonmainly by its different kind of mouthbrooding including sexual dichromatism and dimorphism, arena spawning and separate nursery areas. With few exceptions biogeographical data seem to coincide well. However, indications for parallel developments in breeding habits and species which exhibit characters of both genera show that the present classification may be a tentative one. Dr. TREWAVAS,with examples involving a.o. trophic adaptations and species from thermal environments, makes it quite clear that the unraveling of the relationships between the genera and species is greatly hampered by convergent and parallel evolution. For this reason no cladograms are included. Distinguishing characters of the subgenera of Oreochromisand of the monotypic mouthbrooding genus Danakilia are also given in the introductionary chapters. Com- ments on the subspecies are somewhat inconveniently hidden in an interesting chapter on speciation at the end of the book. After the generic framework has been laid out some 450 pages are dedicated to the description of 12 species of Sarotherodon(2 with 5 subspecies each), 4 subgenera and 32 species of Oreochromis(6 with 2, 1 with 3, and one with seven subspecies) and Danakilia franchettii. These descriptions are sometimes very elaborate, containing chapters on natural distribution and dispersal by man, general ecology, habitat, salinity and temperature tolerance, reproduction and hybridization, food, size and growth, and relationships. In contrast to the extensive ecological information, the morphological 100 descriptions are meagre, containing few morphometric measurements and only super- ficial descriptions of such important morphological characters as the teeth. Throughout, the chapters are illustrated with 187 figures including many maps and representations of at least one specimen of nearly all (sub)species, and 110 tables. Unfortunately the quality of the figures leaves much to be desired: e.g. whole fishes are illustrated with photographs, new drawings and figures from existing literature, the latter especially are of very variable quality. Similarly for the illustration of the lower pharyngeal bone, an element of great importance in the taxonomy of the group, diagrams, drawings, photographs and scanning electron micrographs have been used. As the scanning pictures are of a high quality and very informative one wonders why not all lower pharyngeals were depicted this way. In many cases drawings of teeth are wanting, while figures including jaws or other anatomical features are even more scarce. Apparently the lack of these drawings reflects the fact that as yet relatively little research has been done at the anatomical level, rather amazing in view of the importance of the group in taxonomy and fish culture. Apart from these deficiencies this sec- tion contains a wealth of information as well as lots of useful references and is of great interest not only to those working with tilapias in the field or in museums, but equally to students of cichlid biology and evolution in general. Although Trewavas refers to FRYER& ILES (1972), LOWE-MCCONNELL(1975) and PULLIN& LOWE-MCCONNELL (1982) for more information on the general ecology of tilapias, I believe there is much in her own book not mentioned by these authors or which is seen in a different light. It is unfortunate that one has to search the text for particular information, as the index for this purpose is too limited. In the last part of the book some 20 pages are filled with identification keys including a table with all major African water systems and their naturally indigenous tilapias, and one in which all species are listed with their major distinguishing characters. Before proceeding with the dichotomous keys for Sarotherodonor Oreochromisone should be able to make a distinction between these genera and Tilapia. This is not always easy. A reference to an existing key for Tilapia would have been useful. The dichotomous keys work well if a number of specimens, including adults of both sexes, from one locality are available. The identification of single juvenile specimens remains difficult and is often impossible. Moreover for those working with fishes reared in fish ponds there is the problem of possible hybrids. These are treated in the text but not in the keys. The problem also affects taxonomists because tilapias have been introduced in many African rivers and dams already containing other tilapias. As TREWAVAS writes "the fishes themselves have sometimes failed to distinguish their new neighbours and have interbred". The magnitude of this problem will only increase further in the future. As one who early recognized the need to collect data on the natural distribution of tilapias, Dr. TREWAVASis to be commended for this resulting standard work that will doubtlessly stimulate much research. It is only hoped that the people in Africa whom one would wish to continue the field work are not discouraged from buying it because of its unreasonably high prize. REFERENCES GREENWOOD,P. H., 1978. A review of the pharyngeal apophysis and its significance in the classification of African cichlid fishes. Bull. Br. Mus. nat. Hist. (Zool.) 33 (5): 297-323. FRYER,G. & T. D. ILES, 1972. The cichlid fishes of the great lakes of Africa: their biology and evolution. Oliver & Boyd, Edinburgh, Great Britain. LOWE-McCONNELL,R. H., 1975. Fish communities in tropical freshwaters: their distribution, ecology and evolution. Longman, London, Great Britain. .

Load more