INTESTINE LENGTH IN THE FISHES OF A TROPICAL STREAM .1. ONTOGENIC ALLOMETRY

We examined the ontogenetic allometry of intestine length in relation to body length and body mass in 21 species of fish from forest streams in Panama. The relationships between log(10) intestine length and log (10) body length and mass were well described by linear regressions, a lthough some species showed slight curvilinearity. Slopes and intercep ts of the linear regressions varied considerably among species. Intest ine length was positively allometric in most species, with slopes of t he intestine length:body length relationship ranging from 1.09 to 2.11 . Relative intestine lengths (intestine length/body length) varied by two orders of magnitude (0.39-38.44) in the data set as a whole, but t he variation was about one order of magnitude when species were compar ed at a common body size. Species in which body mass increased more ra pidly with body length had more rapid increases in intestine length wi th body length. Among omnivorous and carnivorous species compared at t he same body length, heavier species had longer intestines. Interspeci fic comparisons of relative intestine length may produce misleading co nclusions unless comparisons are made at a common size and account for differences in relative mass.