Landmark-based morphometric analysis of the body shape of two sympatric species, Ctenopharynx pictus and Otopharynx sp. "heterodon nankhumba" (Teleostei: Cichlidae), from Lake Malawi Daud D. Kassam1*, Tetsu Sato2, and Kosaku Yamaoka1 1 Laboratory of Aquatic Ecology, United Graduate School of Agricultural Science, Ehime University, B 200 Monobe, Nankoku, Kochi 783-8502, Japan (e-mail: DDK,
[email protected]) 2 WWF Japan, Nihonseimei Akabanebashi Building, 6 Fl., 3-1-14 Shiba, Minato-ku, Tokyo 105-0014, Japan Received: May 17, 2001 / Revised: May 22, 2002 / Accepted: June 22, 2002 Abstract Morphological differences in body shape of two sympatric benthophagous cichlid species Ichthyological from Lake Malawi, Ctenopharynx pictus and an undescribed species, Otopharynx sp. “heterodon Research nankhumba,” were investigated using geometric morphometric methods. From digitized data of land mark points on lateral profiles of fishes, the shape of each species was compared by the thin-plate spline ©The Ichthyological Society of Japan 2002 method. Statistical analyses revealed significant variation in both uniform and nonuniform compo nents of shape between the two species. From the splines generated, it was revealed that most of the Ichthyol Res (2002) 49: 340-345 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 coexi stence of the two species through resource partitioning.