Bruno Simmen

Taste Discrimination in Lemurs and Other Primates, and the Relationships to Distribution of Plant Allelochemicals in Different Habitats of Madagascar

This chapter deals with the adaptation of taste responses of lemurs and other primates to different environments, in relation to primary and secondary compounds in potential foodstuffs. Emphasis is placed on the relationship between taste sensibility to sugars and energy expenditure across species. In the most specialized species, the adaptive trends are inferred according to the importance of the deviation from such allometric relationship. The signification of sugar mimics present in some fruits is discussed in terms of coevolution of plants and tasting ability of primates, that, for lemurs, parallels that of platyrrhine monkeys. Taste responses towards other tastants such as sodium chloride are examined in relation to potential risks of deficiency and/or toxicity. Sensitivity to tannins has been investigated in different species, with a two-bottle preference test. We observed large variations that are likely to be adaptive to the concentrations in plant species in various environments. For instance, the rejection threshold for a mixture of tannin and fructose is much higher in Propithecus verreauxi (above 170 g/l) than in Microcebus murinus (0.54 g/l). Recognition thresholds can also vary slightly between human populations, in relation to ancient or recent food practices. There is also a wide range of taste sensitivity towards quinine, without any correlation, in this case, with body mass or other factors related to energy expenditure. Different habitats of Madagascar are compared according to the results of screening tests on tannins and alkaloids. The eastern rain forest (at Andasibe) present slightly lower proportion of plants with alkaloid-like reaction, and a significantly higher proportion of tannin-rich plants than both the gallery forest and the Didiereaceae bush in the south (at Berenty). The results have been related to the gustatory ability of lemur species having to cope with these secondary compounds, and the food niche of the different species.

Changes in Food Neophobia and Food Preferences During a Weight Reduction Session: Influence of Taste Acuity on the Individual Trajectory

Food neophobia, the reluctance to taste novel food, is an adaptive food behavior in evolutionary terms with survival advantages. When measured by the declarative Food Neophobia Scale (FNS) it appears as a personality and heritable trait, thus susceptible to reduce the food repertory and to limit food variety consumption. Inducing changes in food neophobia would eventually overcome this risk. Furthermore, we know that PROP (6-n –propylthiouracil, a bitter chemical substance) sensitivity is genetically determined and can be used as a marker for food preference: greater PROP sensitivity is linked to a reduced consumption of vegetable and fruit consumption – as the foods taste bitter – which has health implications, and could lead to obesity. One study has shown a relationship between PROP sensitivity of Tunisian adults and their preferences and attitudes toward food. We investigated a possible mediation of taste acuity, (assessed using recognition thresholds for sucrose, citric acid, sodium chloride, and PROP) and supra-threshold perceived intensities for these substances on food preferences (assessed by food familiarity and liking questionnaire on different food categories) and FNS (assessed by using the FNS score) in the context of a 10-month residential weight reduction session (WRS) in massively obese adolescents. Taste acuity appeared to mediate behavioral food-related changes during the WRS. High taste acuity was associated with limited reduction in food neophobia whereas less sensitive subjects showed greater increase in the acceptability of healthy foods – especially fruits and vegetables – and greater reduction in food neophobia. Therefore, taste perception (and particularly PROP perception) appears to predict the magnitude of food-related behavioral change achieved during a WRS. A possible relation and/or superimposed effect of food neophobia and PROP sensitivity on food preference and food use are discussed. Application of these findings will be taken into consideration to start a diet program for obese subjects.

Perception gustative et couverture des besoins énergétiques chez les primates

RésuméLa perception gustative permet d’orienter les choix alimentaires des primates dans les différentes niches écologiques où ils ont évolué. Les possibilités de choix sont cependant limitées par le poids corporel des différentes espèces, selon des relations allométriques dont nous présentons les caractéristiques chez les primates strepsirrhiniens et haplorrhiniens comparativement aux autres ordres de mammifères. Le métabolisme, globalement économe en énergie des primates, déterminé avec une précision suffisante chez plusieurs espèces incluant Homo sapiens, ainsi que les déterminants phylogénétiques et allométriques de la perception gustative, permettent de préciser l’origine des variations interspécifiques de la stratégie alimentaire. Les primates testés (dont Homo sapiens) ont une stratégie énergétique économe par rapport aux autres mammifères. Les variations de stratégie alimentaire entre espèces sont analysées ici en fonction des déterminants phylogénétiques et allométriques de la perception gustative.AbstractThe choice of food in primate species is driven by perceptions of taste in the various ecological niches where each species has evolved. However, food choices are limited by the body mass of each species, in accordance with allometric relationships that are presented and discussed here for strepsirrhines and haplorrhines compared to other mammalians. As well as metabolism, for which the energy requirement is generally low in primates and which has been fairly accurately determined for several species including Homo sapiens, the phylogenetic and allometric determinants of perceptions of taste can also be used to determine the origin of interspecies variations in feeding strategies. Primates tested including Homo sapiens share a thrifty energy strategy compared to other mammals. The variations of feeding strategies among species are analyzed here according to the phylogenetic and allometric determinants of taste perception.