Guy G. Teugels

First data on an Index of Biotic Integrity (IBI) based on fish assemblages for the assessment of the impact of deforestation in a tropical West African river system

African tropical rainforests, and especially their freshwater biodiversity, are seriously threatened by ongoing industrial deforestation. Sound ecological management is needed to ensure the sustainability of these resources. For this purpose, an index of biotic integrity (IBI), based on fish assemblage characteristics, is developed in this paper. It is used to quantify the impact of industrial deforestation on freshwater biodiversity. Data from 30 non-impacted sites were used to develop a series of compositional, structural and functional metrics that reflect sites with a high biotic integrity, i.e. what a stream-fish community should look like in the absence of human perturbation. These data were compared to data collected from sites subjected to substantial forest watershed loss, in order to identify those IBI metrics that best distinguish streams with high and low biotic integrity. The overall IBI scores reflected the quality of the watershed conditions. In addition, there was a close agreement between an index of environmental quality, based on water and habitat quality and the IBI scores, suggesting that the different biological responses of the fish assemblages (observed differences in the IBI scores) were indicative of differences in physico-chemical quality of the streams. The ability of the proposed IBI to index water resource degradation, due to deforestation, suggests that it can be used as a tool for biological monitoring. However, more consistent and comprehensive data are needed to further refine the IBI, especially the assignment of integrity classes and metric threshold values.

Preliminary results of a morphological study of five African species of the subgenus Clarias (Clarias) (Pisces; Clariidae)

Summary The results of a morphological study on five nominal species of the subgenus Clarias (Clarias) show clearly that two, C. lazera and C. mossambicus, are synonyms of C. gariepinus (Burchell 1822). Clarias anguillaris is recognized as a valid species, with C. senegalensis as its junior synonym. The subgenus Clarias (Clarias) composed of the species considered here, appears to be a ‘homogeneous’ group on the basis of the head length, the heavily ossified cranium, the pectoral spine serrations etc. (see David 1935). To what extent these characters can be regarded as signifying a monophylectic assemblage and how this assemblage may be related to other clariid groups, must await the results of a further study now being undertaken.

The nomenclature of African Clarias species used in aquaculture

Abstract A new systematic revision of the 120 nominal African Clarias species recognises only 32 valid species. In order to achieve a more uniform nomenclature, this note clarifies the systematic status and the more important synonyms of Clarias gariepinus and C. anguillaris , two species of considerable importance in aquaculture.

Spatial and seasonal distribution of the ichthyofauna of Lake Nokoué, Bénin, west Africa

The fish biodiversity of Lake Nokoué, a lagoon in Bénin, was monitored for one year from August 2000 to July 2001 by means of samples from the artisanal fishery collected once a month at three stations. A total of 5 933 fish weighing 95 322g (mean individual weight 16.0g) belonging to 51 species, 47 genera and 34 families were sampled. An abundance of juveniles was observed, confirming the importance of the lake as nursery grounds, rich in exploitable habitats like other tropical estuaries and lagoons. The fish fauna comprised three main components: i) an estuarine component (strict, freshwater and marine origins) which is the basis of the lagoon fauna community and which is stable in space and time; ii) a marine component containing fishes which appeared in the lagoon during the dry season where the salinity remains high (>20‰) and iii) a freshwater component with fishes coming into the lagoon from the river during the flood period. The magnitude of the spatial and seasonal fluctuations of the last two components varies depending on the area: marine (Zogbo), freshwater (Vêki) or intermediate (Ganvié). The global species richness and the relative abundances of fish vary between stations and from month to month. November, with 20 species on average, and January, with 6 species on average, are significantly different as regards species richness.

Karyological analysis of three strains of the African catfish, Clarias gariepinus (Clariidae), used in aquaculture

Ozouf-Costaz, C., Teugels, G.C. and Legendre. M.. 1990. Karyological analysis of three strains of the African catfish, Clarias gariepinus (Clariidae), used in aquaculture. Aquaculture. 87: 271277. A karyological analysis of three strains of Clarias gariepinus used in fish culture, originating from different localities in Africa and Asia Minor, and thus representing populations from the distribution limits of this species. revealed an identical karyotype, 2n=56 with a pair of heteromorphic sex chromosomes (ZW) and a nucleolus organizer (NOR) location in,a single pair of chromosomes, for all strains. These results confirm the synonymy between C. gariepinus, C. farero and C. mossambicus as introduced by Teugels in 1982.

Phylogeographic patterns in populations of the black-chinned tilapia complex (Teleostei, Cichlidae) from coastal areas in West Africa: support for the refuge zone theory

Within the tilapiines, a major African cichlid lineage, quite limited genetic informations are available on phylogenetic interrelationships and phylogeographical patterns at both macro- and micro-evolutionary scales. The present study examines the genetic diversity of the black-chinned tilapia complex from coastal areas in West Africa (Senegal to Congo-Brazzaville) based on mtDNA control region sequences. Phylogenetic inferences provide support for the monophyly of both taxa involved. It is suggested that Sarotherodon melanotheron and Sarotherodon nigripinnis have diverged probably since the early Pleistocene. The occurrence of the main intraspecific lineages could be dated back to about 500,000-900,000 years. Our data suggest that West African Pleistocene refuge zones may have strongly influenced the degree and level of genetic differentiation among populations and thus the observed phylogeographic patterns. The spatial distribution of mtDNA lineages and the centres of intrapopulational genetic diversity clearly correspond to proposed lowland refuge zones and core areas of Central Africa. Moreover, this study genetically supports the existence of Sarotherodon melanotheron leonensis for the first time and further confirms the validity of the most recently introduced subspecies, e.g., Sarotherodon nigripinnis dolloi.

A systematic revision of the large-scaled Marcusenius with description of a new species from Cameroon (Teleostei; Osteoglossomorpha; Mormyridae)

Nine out of 37 recognized species in the genus Marcusenius have eight large circumpeduncular scales rather than 12 or 16, which is more typical of the genus. They are: M. dundoensis, M. fuscus, M. ghesquierei, M. intermedius, M. kutuensis, M. lambouri, M. moorii, M. paucisquamatus and M. schilthuisiae. All nine are restricted to West-Central and Central Africa. A detailed morphometric analysis could not distinguish differences between M. moorii, M. paucisquamatus and M. lambouri. Therefore they are considered as synonyms with M. morrii as the senior synonym. The systematic status of M. intermedius is uncertain owing to the existence of only three specimens. Within this species complex a new species, Marcusenius sanagaensis, is described from the Sanaga River basin in Cameroon. It differs from all the others in the number of scales on the lateral line and in the extent of the broad dark band between the anterior base of the dorsal fin and the anterior base of the anal fin. All valid Marcusenius species wit...

The Bathyclarias–Clarias species flock. A new model to understand rapid speciation in African Great lakes

Phylogenetic relationships between seven species of the catfish species flock from Lake Malawi (genus Bathyclarias) and other Clariid catfish have been investigated using cytochrome b partial sequences. Here we demonstrate that this species flock originated from a widespread, generalist species, Clarias gariepinus, still occurring in the lake. Bathyclarias species and their ancestor C. gariepinus form a simple model that can be used to understand the mechanisms of adaptation and rapid speciation in African Great lakes.

Genetic Evidence for Monophyly of the Genus Heterobranchus and Paraphyly of the Genus Clarias (Siluriformes, Clariidae)

Abstract A 579 base-pairs fragment of the cytochrome b gene has been sequenced for the four Heterobranchus species, four Clarias species, and Channallabes apus (Clariidae). Clarotes laticeps (Claroteidae) was used as outgroup. Results support the hypothesis that Heterobranchus is monophyletic. Clarias, however, appears to be paraphyletic.

Morphology of the cranial system of Platyclarias machadoi: interdependencies of skull flattening and suspensorial structure in Clariidae

The African catfish Platyclarias machadoi stands out from other clariid species by its extremely dorsoventrally flattened skull. This paper focuses on the spatial constraints and consequent functional interdependencies in this very low skull (average skull height of 27.5±3.0% skull length); such as the medial position of the retroarticular process on the lower jaw, the horizontal position of the suspensorium, the lateral tilting of the pterygoid bones and the anterior part of the quadrate with regard to the suspensorial transverse long axis. These characteristics can be presumed to have major influences on the capacity of suspensorial adduction, influencing the feeding and respiratory mechanisms. A comparison with other clariid species showed that one of the apomorphies is the presence of an extra muscle (musculus adductor mandibulae A3″ pars levator tendinis) in the adductor mandibulae complex. This extra muscle lifts the tendon complex of the adductor mandibulae, resulting in a higher moment on the lower jaw. Some comments on the original species/genus descriptions are given.