Quantitative differences in the chemoreceptor systems in the barbels of two species of Mullidae (Mullus surmuletus and M. barbatus) with different bottom habitats

Abstract

Qualitative and quantitative observations were made of the growth, distribution and density of external taste buds (TB) in the barbels of 2 phylogenetically close species of the Mullidae family (Perciformes: Teleostei) from the NW Mediterranean. Both species live on the continental shell and have similar benthivorous feeding habits, but each prefers a different bottom habitat. Mullus surmuletus is typical of sandy and rocky bottoms, while Mullus barbatus is found over muddy bottoms and reaches to deeper waters than M. surmuletus. The barbels of M. barbatus differ from those of M. surmuletus in that they have a greater density and number of TBs, which are characteristically distributed in well-defined groups. These characteristics of M. barbatus are associated with a greater sensitivity to chemical stimuli, as there is a compensatory relationship with the reduction of the visual field which occurs in muddy and deeper waters