Llama and alpaca comparative sperm head morphometric analysis

South American camelids are classified in four different species included in two genera. Llama (Lama glama L.) and alpaca (Vicunya pacos, L.) are the domestic species, presenting a high economical interest. This classification is based on historical, evolutionary and morphological criteria, but the level of hybridization and the total reproductive compatibility make it difficult to use the “biological criteria” based on reproductive isolation. The aim of the work was to see if there are differences on spermatozoa morphometry indicating a pre-zygotic isolation mechanism based on sperm competition. Nine adult Lanuda (Ch’aku) llamas and eleven Huacaya alpacas were used. After obtaining the samples using an artificial vagina, semen smears were stained with Hemacolor kit. Samples were automatically analysed using the morphometry module of the ISASv1 CASA system. Almost 100 sperm cells were analysed per sample. The following parameters were calculated: Length, Width; Perimeter, Area, Ellipticity, Rugosity, Regularity and Shape Factor. Most of the parameters (except rugosity and regularity) were significantly different between both species, being greater in alpaca than in llama. Looking to the variation data, both intra and inter-animal coefficients of variation (CV) were also different, but in this case the variation was higher in both CV in llama than in alpaca. From the point of view of the sperm competition, all these data would suggest that both species are in the process of a gamete isolation process. A good selection of sperm characteristics could help farmers to define the “purity” of each animal using the morphometrical analysis, not much more effective than other techniques, but much simpler and less expensive.