Olfactory capabilities of sharks: an anatomical and molecular comparative approach

Abstract

Theoretical thesis.Bibliography: pages 52-66.Chapter 1. General introduction -- Chapter 2. Anatomical characteristics of the olfactory organ of sharks -- Chapter 3. Molecular characteristics of the olfactory organ of sharks -- Chapter 4. General discussion -- Final conclusions and further directions -- Supplementary electronic material -- References.Sharks rely heavily on the sense of smell, and their olfactory apparatus has likely evolved to suit the differing lifestyle requirements of each species. Unfortunately, the selective pressures that shape the various physical traits of the olfactory organ of sharks, and their effect on olfactory capabilities, are poorly understood. Here, a multidisciplinary approach combining microscopic and transcriptomic techniques was used to characterise the olfactory organs of two shark species: the pelagic, shortfin mako (Isurus oxyrinchus) and the benthic blind shark (Brachaelurus waddi). The total sensory surface area of the olfactory organs-a traditional proxy of olfactory capabilities-is relatively larger in I. oxyrinchus due to greater coverage of sensory epithelium and more extensive secondary folding of the lamellae. However, examination of the de novo transcriptomes reveals a more diversified olfactory receptor repertoire in B. waddi. These findings suggest that sharks may rely on different olfactory strategies (i.e. more extensive olfactory organs and/or more diversified receptor repertoires) that may be related to the characteristics of the flow within their olfactory organs, their ecology or phylogeny. Consequently, multidisciplinary studies considering the anatomical and molecular traits of the olfactory system of sharks are required to fully comprehend the olfactory capabilities of this group -- abstract.Mode of access: Internet.1 online resource (x, 80 pages) illustration