Morphological variability in the Cuatro Cienegas cichlid,Cichlasomaminckleyi

The endemic cichlids of the Cuatro Cienegas Basin, Coahuila, Mexico are currently grouped in a single polymorphic species,Cichlasoma minckleyi.Twomorphs ofC.minckleyiwere distinguished largely by features of the trophic apparatus, especially the pharyngeal dentition. Variation in body shape, based upon analysis of a set of linear measures, was continuous and did not allow recognition of discrete morphs. Individuals raised in the laboratory on several different diets indicated that trophic morphology had an important genetic component. Individuals raised in the laboratory, however, did not differentiate to the degree seen in comparably sized individuals collected at Cuatro Cienegas. This may be because snails used as food in the experiments were not as hard as endemic snails and indicated that some aspects of trophic morphology were also dependent upon environmental cues. # 2003 The Fisheries Society of the British Isles