Searching for the basic pattern of morphogenesis in the inner ear: study in a basal vertebrate, the shark Scyliorhinus canicula

Abstract

The inner ear is the organ responsible for the detection of sound, balance and acceleration in vertebrates. It is originated from the otic placodes, which transform into the otic vesicle and finally the mature inner ear, composed by the dorsal semicircular canals and the ventral chambers. Despite its common origin and developmental process shared by all the craniates, it presents some particularities in some vertebrate groups. The key phylogenetic position of chondrichthyans in the basis of the gnathostome radiation and the characteristics of its inner ear respect to other gnathostomes, makes them a very interesting model for evo-devo studies about this sense organ. In this study we have developed a simple protocol for analyzing the development of embryos and juveniles of catshark through micro-computed tomography. The high-resolution images obtained allowed us to make a precise description of the morphogenesis of its inner ear and also permitted a better understanding of our results about the spatial expression patterns of different molecular markers.