Spider Monkey Taste Responsiveness to Ten Sweet-Tasting Substances
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Linköping University | Department of Physics, Chemistry and Biology Type of thesis, 60 hp | Educational Program: Physics, Chemistry and Biology Spring term 2020 | LITH-IFM-x-EX— 20/3809--SE Taste responsiveness of black- handed Spider Monkeys (Ateles geoffroyi) to ten substances tasting sweet to humans Sofia Pereira Examiner, Lina Roth Supervisor, Matthias Laska Avdelning, institution Datum Division, Department Date Department of Physics, Chemistry and Biology Linköping University Språk Rapporttyp ISBN Language Report category Svenska/Swedish Licentiatavhandling ISRN: LITH-IFM-x-EX-- 20/3809--SE Engelska/English Examensarbete _________________________________________________________________ C-uppsats D-uppsats Serietitel och serienummer ISSN ________________ Övrig rapport Title of series, numbering ______________________________ _____________ URL för elektronisk version Titel Title Taste responsiveness of black-handed Spider Monkeys (Ateles geoffroyi) to ten substances tasting sweet to humans Författare Author Sofia Pereira Sammanfattning Abstract Studies on taste perception in nonhuman primates contribute to the understanding of the evolution of the sense of taste. To assess the responsiveness of four adult spider monkeys (Ateles geoffroyi) to a set of substances perceived as sweet by humans, two-bottle preference tests were performed to determine taste preference thresholds, and taste-induced facial responses were analyzed. The spider monkeys displayed a significant preference for concentrations as low as 0.2-1 mM acesulfame K, 0.002-0.5 mM alitame, 10- 20 mM isomalt, 0.002-0.5 mM sodium saccharin, 2-20 mM galactose and 20-50 mM sorbitol over water. The spider monkeys were generally unable to perceive aspartame and, based on their facial responses, probably do not perceive it as sweet. Thaumatin and monellin were not detected, and most likely neither was the sweetness of sodium cyclamate. Sodium saccharine and sodium cyclamate were rejected at high concentrations by at least one monkey, which is congruent with the perception of a bitter side taste as reported in humans. A significant correlation was found between the ranking order of sweetening potency for the different substances of spider monkeys and humans, but not between spider monkeys and chimpanzees. The results suggest that spider monkeys may be generally more sensitive than chimpanzees and at least as sensitive as humans to the tested substances, supporting the notion that high sensitivity to sweet taste may be associated with a frugivorous dietary specialization. The lack of responsiveness to some of the substances supports the notion of a dichotomy in sweet-taste perception between platyrrhine and catarrhine primates. Nyckelord Keyword Ateles geoffroyi, spider monkeys, sweet-tasting substances, taste preference thresholds Contents 1. Abstract ................................................................................................................................. 6 2. Introduction .......................................................................................................................... 6 3. Materials and Methods ........................................................................................................ 9 3.1. Determination of taste preference thresholds in spider monkeys 3.1.1. Animals and housing .................................................................................................... 9 3.1.2. Taste stimuli ................................................................................................................. 9 3.1.3. Experimental procedure ............................................................................................. 13 3.1.4. Data analysis .............................................................................................................. 14 3.2. Determination of taste detection thresholds in humans 3.2.1. Subjects....................................................................................................................... 15 3.2.2. Taste stimuli ............................................................................................................... 15 3.2.3. Experimental procedure ............................................................................................. 15 3.2.4. Data analysis .............................................................................................................. 15 3.3. Analysis of taste-induced facial responses in spider monkeys 3.3.1. Animals and housing .................................................................................................. 16 3.3.2. Taste stimuli ............................................................................................................... 16 3.3.3. Experimental procedure ............................................................................................. 17 3.3.4. Data analysis .............................................................................................................. 19 4. Results ................................................................................................................................. 19 4.1. Taste preference thresholds of spider monkeys 4.1.1. Artificial sweeteners ................................................................................................... 19 4.1.2. Sweet-tasting proteins ................................................................................................ 21 4.1.3. Sweet-tasting saccharides .......................................................................................... 22 4.1.4. Interindividual variability .......................................................................................... 23 4.2. Taste detection thresholds of human subjects 4.2.1. Thresholds for alitame and isomalt ............................................................................ 24 4.2.2. Interindividual variability .......................................................................................... 25 4.3. Taste-induced facial responses in spider monkeys 4.3.1. Inter-rater agreement ................................................................................................. 25 4.3.2. Group-level analysis .................................................................................................. 25 5. Discussion............................................................................................................................ 31 5.1. Within-species comparison of taste preference thresholds between sweeteners .......... 31 5.2. Comparison of sweetening potency order between spider monkeys, humans and chimpanzees...................................................................................................................... 34 5.3. Between-species comparisons of taste preference thresholds ....................................... 35 5.3.1. Artificial sweeteners ............................................................................................... 35 5.3.2. Sweet-tasting proteins............................................................................................. 42 5.3.3. Sweet-tasting saccharides....................................................................................... 45 5.4. Spider monkeys' perception of aspartame as indicated through facial reactivity ......... 47 5.5. Conclusions ................................................................................................................... 51 6. Societal and ethical considerations ................................................................................... 52 7. Acknowledgements ............................................................................................................ 53 8. References ........................................................................................................................... 54 Appendix ................................................................................................................................. 61 1. Abstract Studies on taste perception in nonhuman primates contribute to the understanding of the evolution of the sense of taste. To assess the responsiveness of four adult spider monkeys (Ateles geoffroyi) to a set of substances perceived as sweet by humans, two-bottle preference tests were performed to determine taste preference thresholds, and taste-induced facial responses were analyzed. The spider monkeys displayed a significant preference for concentrations as low as 0.2-1 mM acesulfame K, 0.002-0.5 mM alitame, 10-20 mM isomalt, 0.002-0.5 mM sodium saccharin, 2-20 mM galactose and 20-50 mM sorbitol over water. The spider monkeys were generally unable to perceive aspartame and, based on their facial responses, probably do not perceive it as sweet. Thaumatin and monellin were not detected, and most likely neither was the sweetness of sodium cyclamate. Sodium saccharine and sodium cyclamate were rejected at high concentrations by at least one monkey, which is congruent with the perception of a bitter side taste as reported in humans. A significant correlation was found between the ranking order of sweetening potency for the different substances of spider monkeys and humans, but not between spider monkeys and chimpanzees. The results suggest that spider monkeys may be generally more sensitive than chimpanzees and at least as sensitive as humans to the tested substances, supporting the notion that high sensitivity to sweet taste may be associated with a frugivorous dietary specialization. The