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 non-uniform 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 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.