Shape variation in trophic morphology between species in two trophic guilds (zooplankton
and epilithic algal feeders) was investigated using landmark-based geometric morphometrics.
Three disarticulated bone elements from the head region were examined; the neurocranium,
the premaxilla and lower jaw. From separate analyses of each bone element, significant
shape variation was identified between species in each trophic guild. The deformation
grids generated revealed that, for the zooplankton feeders, Ctenopharynx pictus
has a longer neurocranium, a longer and ventrally directed vomer, a larger orbit, a
shorter ascending arm, a shorter maxillad spine, and a more compressed articular bone
relative to Copadichromis borleyi. In algal feeders, Labeotropheus fuelleborni
has a shorter neurocranium, a smaller orbit, a ventrally directed vomer, a longer
ascending arm, a shorter dentigerous arm, increased height of the articular process,
and a more elongated dentary than Petrotilapia genalutea. Observed anatomical
differences are discussed in terms of function, specifically with respect to the
feeding microhabitat differentiation between species in each trophic guild. These
differences enable us to appreciate the role that trophic morphology plays in enhancing
ecological segregation, leading to coexistence of the species.