Dietary, Phylogenetic, and Ecological Correlates of Intestinal Sucrase and Maltase Activity in Birds

Publisher Website
Google Scholar
Abstract
Intestinal sucrase and maltase activities were measured in three species of hummingbirds and 11 species of passerine birds from western Mexico. Maximal sucrase activity standardized by nominal area of intestine was 2-118 times higher in hummingbirds than in the nine species of passerines that showed significant sucrase activity. Two species of passerines (Turdus rufopalliatus and Catharus aurantiirostris) lacked significant sucrase activity. Lack of functional sucrase activity has been reported in five species of passerine birds restricted to three closely related families (Muscicapidae, Sturnidae, and Mimidae). Interspecific variation in sucrase activity is probably influenced both by feeding habits and phylogenetic affinities. No allometric relation between sucrose hydrolysis capacity and body mass was found. When the two species with no significant sucrase activity were deleted from the sample, maltose hydrolytic capacity and body mass were allometrically related (exponent = 0.65). Maltase and sucrase activity were linearly correlated. Hummingbirds and passerines differed in the relationship between maltase and sucrase activities. It can be hypothesized that this difference is because the sucrase-isomaltase enzyme complex of hummingbirds has less maltase activity than that of passerines. The apparent affinity of sucrase varied almost 10-fold among species. This variation probably does not reflect differences in "real" affinity (i.e., the affinity of sucrase in solution) but can be attributed to unstirred-layer effects resulting from sucrase's being a membrane-bound enzyme. The presence or absence of sucrase activity in birds can have behavioral and ecological consequences. Birds lacking sucrase activity reject foods containing sucrose. The absence of sucrose in the pulp of bird-dispersed fruits can be partially explained by the lack of sucrase activity in bird frugivores.

This publication has 0 references indexed in Scilit: