Feeding specialization in Herichthys minckleyi: a trophically polymorphic fish
Abstract:Diet specialization in the trophically polymorphic cichlid fish Herichthys minckleyi was examined using gut contents. Individual H. minckleyi were categorized as having molariform, papilliform or undetermined pharyngeal jaws. The presence of enlarged flattened pharyngeal jaw teeth was used to categorize H. minckleyi as molariform, and the possession of only small pencil‐like pharyngeal teeth was used to classify fish as papilliform. Undetermined individuals (<50 mm standard length, LS) were not assigned to one of the two larger morphotypes. Arthropods were found to be generally rare in H. minckleyi gut contents, but when present, they were most frequently recovered from undetermined individuals. The percentage of plant material consumed by undetermined H. minckleyi was not as great as papilliforms ingested on average, and snail crushing by undetermined H. minckleyi was not evident. A significantly greater mean percentage of plant detritus was recovered from papilliforms compared to molariforms. Snails were crushed by molariforms more frequently than by papilliforms. When only molariforms and papilliforms that had crushed snails were compared, a greater number of snails were crushed by molariforms. No relationship was found between molariform LS and the number of snails crushed, but greater molariform tooth number, adjusted for LS, was indicative of recent snail crushing. The maintenance of H. minckleyi pharyngeal jaw variation could be promoted by intraspecific diet differentiation.
Document Type: Regular Paper
Affiliations: 1: School of Biology, Georgia Institute of Technology, Atlanta, Georgia 30332, U.S.A., 2: Department of Biological Sciences and Merriam Powell Center for Environmental Research, Northern Arizona University, Flagstaff, Arizona 86011, U.S.A., 3: Section of Integrative Biology and Texas Memorial Museum, University of Texas, Texas Natural History Collections, Austin, Texas, 78758, U.S.A., 4: University of Alberta, Biological Sciences Centre, CW 405, Edmonton, Alberta T6G 2E9, Canada, 5: Texas Commission on Environmental Quality, MC-160, Austin, Texas 78711, U.S.A. and 6: Texas State University, San Marcos, Texas 78666, U.S.A.
Publication date: 2006-05-01