Landmark-based morphometric analysis of the body shape of two sympatric species, Ctenopharynx pictus and Otopharynx sp. “heterodon nankhumba” (Teleostei: Cichlidae), from Lake Malawi
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Morphological differences in body shape of two sympatric benthophagous cichlid species from Lake Malawi, Ctenopharynx pictus and an undescribed species, Otopharynx sp. “heterodon nankhumba,” were investigated using geometric morphometric methods. From digitized data of landmark points on lateral profiles of fishes, the shape of each species was compared by the thin-plate spline method. Statistical analyses revealed significant variation in both uniform and nonuniform components of shape between the two species. From the splines generated, it was revealed that most of the significant variation between the two species occurs in the head region. Specifically, C. pictus has a longer and deeper head than Otopharynx sp. In addition, the mouth of C. pictus is larger than that of Otopharynx sp. In the trunk region, C. pictus has a shorter abdominal cavity, which may indicate possession of shorter intestines than Otopharynx sp. The variation in gross head morphology and intestinal length may reflect interspecific differences in trophic ecology, possibly facilitating the coexistence of the two species through resource partitioning.
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