PRESENCE OF ENAMEL ON THE INCISORS OF THE LLAMA (LAMA-GLAMA) AND ALPACA (LAMA-PACOS)

Attempts have been made to define the relationships among the South Am erican camelids, the guanaco, llama, alpaca, and vicuna, by comparing the morphology of their incisors, The alpaca has been reported to have an incisor morphology similar to the vicuna, lacking enamel on the li ngual surface, The llama and guanaco are said to have enamel on both t he labial and lingual surface of their incisor teeth, These comparison s have been based on gross morphological observations and not on histo logic analysis. This study was undertaken to determine whether or not alpaca teeth have enamel on the lingual surface, The cross-sectional h istologic anatomy of the incisor teeth was compared in two closely rel ated South American camelid species, the llama (Lama glama), and the a lpaca (Lama paces), Thick sections (300 mu m) and scanning electron mi croscopy were the techniques utilized, The mandibular first, second, a nd third incisors were examined in four llamas and five alpacas, A sub stantial layer of enamel was present on all surfaces of all llama inci sors, The enamel layer on the labial surface of the alpaca incisors cl osely resembled that found in the llama, The enamel layer on the lingu al surface of the alpaca incisors, although greatly reduced, was disti nctly present. Alpacas may be more closely related to guanacos and lla mas than to vicunas. A histologic study of vicuna incisors would help to better define the relationships of the four camelids. (C) 1997 Wile y-Liss, Inc.