Is sugar as sweet to the palate asseeds are appetizing to the belly? : Taste responsiveness to seven sweet-tastingsubstances in white-faced sakis (Pithecia pithecia)

Differences in taste perception between species are thought to reflect evolutionaryadaptations to dietary specializations such as seed predation. By employing a two-bottlepreference test, the purpose of the current study was to evaluate the taste responsiveness forfive food-associated carbohydrates and two steviol glycosides in four adult white-faced sakis(Pithecia pithecia). The taste preference thresholds were found to be 10 mM for sucrose, 10-40 mM for fructose, 20-30 mM for glucose and maltose, and 30-40 mM for lactose. The sakisalso showed a clear preference for rebaudioside A and stevioside over tap water atconcentrations as low as 0.04 and 0.2-0.5 mM, respectively. When given the choice betweenall binary combinations of the five carbohydrates at equimolar concentrations of 100, 200,and 300 mM, respectively, the sakis displayed the following preference pattern: sucrose >fructose > glucose ≥ maltose = lactose. The obtained taste preference thresholds for foodassociated carbohydrates fall into the lower range of values among primates, suggesting acomparatively high sweet-taste sensitivity in the sakis. The pattern of relative preferenceswas consistent with that reported in most tested primates. Altogether, the responsivenesstowards the sweet-tasting substances obtained in this seed predator resembles the resultsobtained in primates which act as seed dispersers. However, these results might reflect anevolutionary adaptation of white-faced sakis to exploit resources containing low sugarconcentrations such as unripe fruits and seeds