A COMPARISON OF THE DEVELOPMENT OF THE LATERAL LINE CANAL PORES IN TWO SPECIES OF CICHLID FISHES WITH FUNCTIONALLY DISTINCT CANAL MORPHOLOGIES

Abstract

The cranial lateral line system (LL) is composed of a series of bony, pored canals that are integrated within a conserved subset of dermatocranial bones. Neuromast receptor organs are located in the canals between positions of adjacent canal pores, which link the fluid within the canals to the fluid of the external environment. Among species the lateral line canals can be narrow, narrow with widened tubules, widened, branched, or reduced. The goal of this project was to examine ontogenetic trends in size and shape of canal pores within and between two cichlid species, Aulonocara stuartgranti (widened canals) and Tramitichromis sp. (narrow canals). Pore placement and size are thought to have functional implications for canal neuromast function, and therefore has implications on behavior. Thus, ontogenetic changes in pore number, size, and shape deserve study. Several hypotheses concerning ontogenetic trends in pore size, area, and inter-pore distance were tested using the pores of the supraorbital and mandibular canals. The data presented here are the first of their kind, showing ontogenetic trends of pore morphology from the larval stage (using histological analysis), through the juvenile and adult stages (using methylene blue stained and cleared and stained specimens). Results show differences in trends between species and within species among pore types (bony, epithelial) where bony pores are larger, in general, than epithelial pores and Aulonocara have larger pores than Tramitichromis. In most instances, similar trends are seen in larvae, juveniles, and young adults.