FUNCTIONAL-CHANGES IN THE ANATOMY OF THE PHARYNGEAL JAW APPARATUS OF ASTATOREOCHROMIS-ALLUAUDI (PISCES, CICHLIDAE), AND THEIR EFFECTS ON ADJACENT STRUCTURES

Organisms are tightly packed with structures so architectonic interdep endency of structures is an obvious aspect of integration. This aspect of functional morphology, however. has received remarkably little att ention. The present paper presents an example of the spatial relations among several apparatuses in the head of the cichlid fish, Astatareoc hromis alluaudi. It investigates the transformations of these apparatu ses and their functions due to a change in the pharyngeal jaw apparatu s resulting from a functional shift (insect eating to snail crushing o r vice versa). The volume of the pharyngeal jaw apparatus differs 55% between the insect eating- and the snail eating morph. The increase in volume of the pharyngeal jaw apparatus has an impressive number of sp atial effects, both direct and indirect on other structures. Reallocat ion of space within the pharyngeal jaw apparatus occurs. Total head Vo lume increases 31% but a reallocation of space is still necessary as t he increase of the opercular compartment where the pharyngeal jaw appa ratus is situated compensates for only 59% of the Volume increase of t hat. Not all spatial effects do impose constraints. Spatial constraint s are avoided when one of the apparatuses can use a topographically di fferent volume of space. The respiratory apparatus shows internal real locations of space without. loss of total volume. The same solution oc curs for elements of the expansion apparatus and the buccal cavity. Th e eyes are not influenced. Finally spatial effects can have positive r epercussions. The muscles of the oral jaw apparatus increase in size. This may be an example of an epiphenomenon. (C) 1996 The Linnean Socie ty of London