Comparison of the Saccules and Lagenae in six macrourid fishes from different deep-sea habitats

Abstract

The structures of inner ears were compared between six species of Macrouridae (grenadiers and rattails) that live at different ocean depths ranging from 200 to 5000 meters. The goal of this comparison is to find out if there are structural differences in their inner ears related to the depth of habitat. The size of the saccular otolith relative to fish head length varies considerably among the six species; with the largest otolith found in Nezumia aequalis and the smallest in N. parini, a mesopelagic species. N. aequalis is a species with potential sound production and auditory dominance by its drumming muscle on the swim bladder. Its saccular sensory area is four times larger than those from the two species live in shallower depths and have vision as their dominant sense (N. parini and Coryphaenoides rupestris). The differences found in the saccule and lagena of these species reflect the sensory advantages of habitats that are related to the benefits and constraints at different depths. It also reflects the fish’s particular life style and the trade-off among different sensory systems. The most obvious trade-off among sensory systems is found between vision and hearing.