On the sense of taste in two malagasy primates (microcebus murinus and eulemur mongoz)

The relationship between phylogeny and taste is of growing interest. In this study we present recordings from the chorda tympani proper (CT) nerve of two lemuriforme primates, the lesser mouse lemur (Microcebus murinus) and the mongoose lemur (Eulemur mongoz), to an array of taste stimuli which included the sweeteners acesulfame-K, alitame, aspartame, D-glucose, dulcin, monellin, neohesperidin dihydrochalcone (NHDHC), saccharin, sodium superaspartame, stevioside, sucralose (TGS), sucrose, suosan, thaumatin and xylitol, as well as the non-sweet stimuli NaC1, citric acid, tannin and quinine hydrochloride. In M.murinus the effects of the taste modifiers gymnemic acid and miraculin on the CT response were recorded. Conditioned taste aversion (CTA) experiments in M.murinus and two-bottle preference (TBP) tests in E.mongoz were also conducted. We found that all of the above tastants except thaumatin elicited a CT response in both species. The CTA technique showed that M.murinus generalized from sucrose to monellin but not to thaumatin. The intake of aspartame, ranging in concentration from 0.1 to 30 mM was measured in E.mongoz with TBP tests. At no concentration did we see a preference, but there was a significant rejection of 10 and 30 mM aspartame (P←0.025). Miraculin had no effects on the CT response to acids, and gymnemic acid did not selectively suppress the CT response to sucrose or that of any other sweeteners. The absence of ability to taste thaumatin in these species supports the dichotomy between catarrhine and non-catarrhine species. The difference in results with thaumatin and monellin indicate that their sweet moieties are not identical. It also points to a phylogenetic difference in taste within the prosimian group. Further, the results with aspartame indicate that the perception of sweetness from aspartame is limited to catarrhine species. Finally, neither miraculin nor gymnemic acid exhibit the same taste modifying effects in lemuriformes as they do in hominoidea. Thus the results with gymnemic acid and miraculin corroborate those obtained earlier in other prosimians.