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The rock-dwelling cichlids from Lake Malaŵi, known as mbuna, comprise a diverse group of haplochromine fishes that are placed among 14 genera. Within the mbuna, Pseudotropheus is a polyphyletic genus, which has served as a catch-all for many of these fishes. Recently, many of the species-groups within Pseudotropheus have been elevated to separate genera. Herein, we describe an elongate form that was originally placed in the Pseudotropheus elongatus species group but is now described as a member of Metriaclima.

Metriaclima is the most speciose genus of rock-dwelling fishes (mbuna) found in Lake Malaŵi with 32 described species and with about 40 recognized forms that still await formal description. The genus is comprised of many geographically narrow populations restricted to specific habitat landmarks, such as reefs or islands. A few species have taken to the open sandy habitat where empty gastropod shells provide shelter. Two species of such shell-dwellers are here described as new. A combination of a black submarginal band in the dorsal and anal fins and five or fewer bars on the flank distinguishes Metriaclima ngarae sp. n. and M. gallireyae sp. n. from all other species of Metriaclima. Metriaclima ngarae sp. n. differs from M. gallireyae by a greater interorbital width and by a greater ratio of the snout length in the distance between snout tip and pelvic fin origin. Adult males of M. gallireyae have a blue-brown overall coloration obscuring the bar pattern on the flank while males of M. ngarae and those of the closely related M. lanisticola retain the bar pattern and have a coloration very similar to that of females.

A species of haplochromine cichlid fish of the genus Diplotaxodon Trewavas, endemic to Lake Malaŵi is described: Diplotaxodon dentatus, new species. All eight type specimens were trawled together off Thumbi East Island in the Southeastern arm of the lake at 73 meters in 1985. They were initially identified as D. argenteus because the teeth on the oral jaws were fully exposed with a closed mouth. The shorter snout length of D. dentatus (26.6–29.2 % HL) clearly separates it from D. argenteus (31.7–34.2 % HL). A plot of a principal components analysis further supports the separation of D. dentatus from D. argenteus.

Cichlids inhabiting the Great Lakes of Africa have radiated extremely rapidly, with Lake Malaŵi harboring some 850 species. This rapid radiation may be linked to the diversity in behaviors, sexual selection, and phenotypic plasticity. To determine the relationships between morphology and behaviors, microcomputed tomography (microCT) was used to observe internal morphological structures. Observed morphological adaptations were linked with observed behavior of cichlids in Lake Malaŵi with respect to the various available food resources. Many of these adaptations have parallels, sometimes into the finest details, in other drainage systems and can thus be considered as variations of how cichlids in general respond to environmental opportunities and challenges. Variations in the structure and teeth of the pharyngeal jaws and the oral jaws allowed for fine tuning of specializations, so that various species can utilize the same source without direct competition. We suggested that high‐resolution X‐ray computed tomography will permit scientists to infer life history and behavior characters of rare or extinct taxa from a detailed examination of morphology and linkages between morphology and behavior found in extant species., We linked observed morphological traits with behavioral observations of fishes from Lake Malawi. We used microcomputed tomography to obtain morphological traits and SCUBA to record behavior.

Two species of haplochromine cichlid fishes of the genus Diplotaxodon Trewavas, endemic to Lake Malaŵi are described: Diplotaxodon longimaxilla, new species, and Diplotaxodon altus, new species. Diplotaxodon altus is diagnosed from other species in the genus based on body depth (35.1–37.8% SL), number of gill rakers (21–26), and a smaller cheek depth (18.2–20.0% HL). Diplotaxodon longimaxilla is delimited from other Diplotaxodon spp. based on body depth (28.9–32.4% SL), horizontal eye diameter (HED 27.1–32.1% HL), smaller cheek depth (15.2–19.4% HL), and number of lateral-line scales (35–38). Other authors have indicated that several other Diplotaxodon spp. occur, but too few specimens were available to permit detailed comparisons. The two new species occur sympatrically at depths of between 40–130 m. Specimens of Diplotaxodon altus were sampled from nets deployed at night using light attraction, while specimens of D. longimaxilla were sampled from nets operated both at night and day. We further ...

Lake Malawi is known for its endemic haplochromine species flock, most notably the rock-dwelling cichlids known as mbuna. The group of mbuna referred to as the Pseudotropheus elongatus species group is currently comprised of Metriaclima spp., Tropheops spp., Cynotilapia spp., and Pseudotropheus spp. In this study, Chindongo , a new genus with the type species C. bellicosus , is described for additional species in this group. Chindongo is distinguished from other mbuna genera by 1) the presence of bicuspid teeth in the anterior portion of the outer row of both upper and lower jaw; 2) a moderately to steeply sloped vomer with a narrow rostral tip which makes an angle of between 53° and 68° with the parasphenoid; 3) a small mouth with the lower jaw slightly shorter than the upper; 4) a broad anterior dentigerous area on both premaxilla and dentary with three or more rows of teeth (usually 5–6 rows); 5) a flank melanin pattern consisting of vertical bars without horizontal elements at any stage of development. Chindongo bellicosus is distinguished by its color pattern and shallower body from the other species which we have transferred to Chindongo . We also describe six new elongate mbuna species and place them into three available genera, they include: Metriaclima flavicauda , M. usisyae , Tropheops kumwera , T. biriwera , T. kamtambo , and Cynotilapia chilundu .

Pseudotropheus livingstonii and P. elegans are two sand-dwelling cichlid species that belong to the so-called mbuna, a group of predominantly rock-dwelling haplochromines of Lake Malaŵi. The identity of these two species has confused taxonomists for almost a century until a recent rediscovery of representatives of P. elegans close to its type locality. New diagnoses for both species are provided.

Species of Stigmatochomis are haplochromine cichlids endemic to Lake Malaŵi, and the genus currently includes four species, S. woodi (type species), S. modestus, S. pholidophorus, and S. pleurospilus. The latter two are known from only their holotypes. Herein, we describe two additional species, Stigmatochromis macrorhynchos and Stigmatochromis melanchros from southern Lake Malaŵi.

We have observed a dramatic decrease in the abundance of snail-eating fishes and an increase in the prevalence of schistosomiasis among village residents and expatriate tourists at Lake Malawi, Africa, over the past two decades. We hypothesized that these observations were linked by a cause-and-effect relationship and that the observed decrease in fish molluscivores permitted an increase in the abundance of snails that are intermediate hosts to schistosomes; we proposed a sampling protocol to determine these relationships. Initially, we thought that intensive study of the interactions among fish, intermediate-host snails, and human schistosomes in southern Lake Malawi could be applied to other areas throughout the lake. More than two-thirds of the cichlid species in Lake Malawi are undescribed, the taxonomy of the Bulinus snails is poorly known, and not all strains of Schistosoma hematobium have been identified. Before we can identify the interactions among these components of the system and effe...

Lake Malaŵi is known for its endemic haplochromine species flock, most notably the rock-dwelling cichlids known as mbuna. One of the larger genera of mbuna is Metriaclima, a group consisting of 31 described species (including the five described herein) and approximately 45 recognized unique populations. Metriaclima is diagnosed by its feeding behavior and several morphological characteristics including the angle of the vomer and the presence of bicuspid teeth in the outer row of both the upper and lower jaws. Metriaclima zebra, the type species for the genus, was described based on a single specimen. While the collection location of this holotype is not known, based on the travel records of its collector, it is likely that the specimen originated from Likoma Island. The holotype was therefore compared to specimens from several localities around this island and was found to be morphologically indistinguishable from some of these. This study includes the morphological analysis of 496 specimens of Metriaclima belonging to 31 collections from Lake Malaŵi. Morphometric differences were analyzed and the relationships among several distinguishable populations of Metriaclima zebra were investigated. Our study further resulted in the description of the following five new species belonging to the M. zebra species complex: M. pambazuko, M. lundoense, M. midomo, M. tarakiki, and M. nigrodorsalis. These species were distinguished and described based on color patterns, morphometric, meristic, and ecological differences. These new species were compared with and distinguished from nearby populations of Metriaclima having similar pigmentation patterns and/or similar ecological niches. An artificial dichotomous key to the described species of Metriaclima is presented.

Prior to 1985, the open waters of Lake Malawi were free from schistosome transmission. Over the past decades, however, the prevalence of urinary schistosomiasis has increased dramatically in the southern part of the lake. We found the prevalence of human schistosomiasis in school-aged children to be negatively correlated with the density of molluscivorous fishes. Specifically, the increased infection rate in southern Lake Malawi between 1978 and 1991 is coincident with the reduction in numbers of snail-eating fishes. During 2003, we determined the relative abundance of molluscivorous fishes and snail density at 18 sites throughout the lake and schistosome infection in school-aged children living in selected lakeshore communities of Lake Malawi. At the 18 sites sampled in 2003, we found that snail abundance decreased with an increase in abundance of snail-eating fishes. Furthermore, the 2003 samples showed that the abundance of snail-eating fishes increased and there was a reduction in schistosomiasis in school-aged children in Chembe Village. We believe that we will not observe a return to the 1978 infection rates until these fishes continue to increase and inhabit shallower waters.

The Lake Malaŵi genus Melanochromis included five species at its inception and was originally distinguished from Pseudotropheus on the basis of morphology, including the arrangement of teeth on the lower pharyngeal bone. Thediagnosis has been extended twice, first to include all elongate mbuna that possess horizontal stripes and U-shaped toothbands and later to exclude mbuna that do not exhibit a sex-related reversal in their colour pattern. Recently, the diagnosisof the genus was refined on the basis of the melanin pattern. The genus now includes only species with a basic melaninpattern, which consists of two black horizontal lateral stripes on a light background. Most adult members of the genus,thus defined, have a sex-related reversal of pigmentation pattern. Here we describe Melanochromis mpoto n. sp. from thenorthwestern part of Lake Malawi, synonymize M. parallelus Burgess & Axelrod 1976 with M. loriae Johnson 1975,redescribe M. chipokae Johnson 1975 and M. robustus Johnson 1985, and reclassify and designate a lectotype for M. brevis Trewavas, 1935.

Schistosomiasis (bilharziasis) transmission due to Schistosoma haematobium has for many years been known to occur along protected shorelines in Lake Malawi, but the recent finding that transmission also can also occur along open shorelines with sandy sediment has had a detrimental effect on tourism to Lake Malawi. The present paper shows that transmission, as evidenced from presence of intermediate hosts, along open shorelines is occurring in the southern part of the Lake. Relatively simple precautions can be taken to ensure minimal risk of attracting schistosome infection, and the schistosomiasis risk should not deter people from visiting and diving in Lake Malawi. African Journal of Aquatic Science 2004, 29(1): 117–119

Lake Mala i is known for its endemic haplochromine species flock, most notably the rock-dwelling cichlids known as mbuna. One of the larger genera of mbuna is Metriaclima, a group consisting of 31 described species (including the five described herein) and approximately 45 recognized unique populations. Metriaclima is diagnosed by its feeding behavior and several morphological characteristics including the angle of the vomer and the presence of bicuspid teeth in the outer row of both the upper and lower jaws. Metriaclima zebra, the type species for the genus, was described based on a single specimen. While the collection location of this holotype is not known, based on the travel records of its collector, it is likely that the specimen originated from Likoma Island. The holotype was therefore compared to specimens from several localities around this island and was found to be morphologically indistinguishable from some of these. This study includes the morphological analysis of 496 specimens of Metriaclima belonging to 31 collections from Lake Mala i. Morphometric differences were analyzed and the relationships among several distinguishable populations of Metriaclima zebra were investigated. Our study further resulted in the description of the following five new species belonging to the M. zebra species complex: M. pambazuko, M. lundoense, M. midomo, M. tarakiki, and M. nigrodorsalis. These species were distinguished and described based on color patterns, morphometric, meristic, and ecological differences. These new species were compared with and distinguished from nearby populations of Metriaclima having similar pigmentation patterns and/or similar ecological niches. An artificial dichotomous key to the described species of Metriaclima is presented.

Five new species of rock-dwelling cichlids from Lake Malaŵi are described. All five species phenotypically resemble Metriaclima aurora based on the absence of a black band in the dorsal fin and occupying the rock-sand interface of the lake. Differences in overall shape, meristics, and coloration distinguish these new species from each other and from previously described species within this group. The new species Metriaclima glaucos, M. mossambicus, M. nkhunguensis, and M. xanthos originate from the Mozambique coast of the lake, while M. sciasma is restricted to Tanzanian waters.

The Lake Malaŵi genus Melanochromis included five species at its inception and was originally distinguished from Pseudotropheus on the basis of morphology including the arrangement of pharyngeal teeth. The diagnosis has been extended twice, first to include all elongate mbuna that possess horizontal stripes and U-shaped tooth bands and later to exclude mbuna that do not exhibit a sex-related reversal in their color pattern. We have further refined the diagnosis of the genus on the basis of the melanin pattern, resolved a longstanding dispute regarding the validity of M. heterochromis, re-evaluated the status of M. vermivorus, synonymized M. mellitus Johnson 1976 with M. melanopterus Trewavas 1935, moved M. benetos Bowers and Stauffer 1977 to Pseudotropheus, and described M. kaskazini, M. wochepa, and M. mossambiquensis from the eastern shore of the lake. Melanochromis is still paraphyletic as two species, M. joanjohnsonae Johnson 1974 and M. labrosus Trewavas 1935, are not congruent with the rest of the group, but, currently, a better alternative for these two could not be found.