The role of olfaction throughout juvenile development: Functional adaptations in elasmobranchs

Abstract

Seven elasmobranch species, a group known for their highly-developed sense of smell, were examined for developmental changes in the number of olfactory lamellae, the size of the surface area of the sensory olfactory epithelium and the mass of both the olfactory rosettes (primary input to the CNS), and the olfactory bulbs. Within each species, juveniles possessed miniature versions of the adult olfactory organs, visually not distinguishable from these and without any obvious structural differences (e.g., with respect to the number of lamellae and the extent of secondary folding) between differently sized individuals. The size of the olfactory organs was positively correlated with body length and body mass, although few species showed proportional size scaling. In Aetobatus narinari and Aptychotrema rostrata, olfactory structures increased in proportion to body size. With respect to the growth of the olfactory bulb, all species showed allometric but not proportional growth. Olfaction may be of particular importance to juveniles in general, which are often subjected to heavy predation rates and fierce inter/intraspecific competition. Accordingly, it would be advantageous to possess a fully functional olfactory system early on in development. Slow growth rates of olfactory structures could then be attributed to a greater reliance on other sensory systems with increasing age or simply be regarded as maintaining an already optimized olfactory system.

Olfactory morphology and physiology of elasmobranchs

“…Whereas lamellar surface area increases with body size of an elasmobranch, the number of lamellae does not; therefore, body size was not included as a covariate during analyses (Fishelson and Baranes, 1997;Schluessel et al, 2010). Our results corroborate those of previous studies, which found interspecific differences in the number of lamellae and surface area for elasmobranchs (Kajiura et al, 2005;Schluessel et al, 2008;Theiss et al, 2009).…”

Clarification of the Terminology of the Olfactory Lamellae in Chondrichthyes

“…The peripheral olfactory organ of Chondrichthyes, the olfactory rosette, is located in the olfactory chamber and it is characterized by a central support called the raphe, which bears folds, which bear smaller, secondary folds (Holl, ; Meng and Yin, ; Theisen et al, ; Zeiske et al, ; Savel'ev and Chernikov, ; Takami et al, ; Fishelson and Baranes, ; Kajiura et al, ; Schluessel et al, ; Theiss et al, ; Abel et al, ; Schluessel et al, ; Timm and Fish, ; Cox, ; Howard et al, ; Ferrando et al, ).…”

“…(e) Two facing folds and the slice of raphe between them is considered an olfactory lamella in some other papers regarding Elasmobranchii with elongated raphe. 1 Asai, ; 2 Holl, ; 3 Meng and Yin ; 4 Meng and Yin, ; 5 Theisen et al, ; 6 Zeiske et al, ; 7 Takami et al, ; 8 Fishelson and Baranes, ; 9 Kajiura et al, ; 10 Schluessel et al, ; 11 Theiss et al, ; 12 Abel et al, ; 13 Meredith and Kajiura, ; 14 Schluessel et al, ; 15 Arif, ; 16 Cox, ; 17 Howard et al, ; 18 Rygg et al, ; 19 Ferrando et al, ; 20 Ferrando et al, . CC = connective capsule; F = fold; R = raphe.…”

Morphofunctional Adaptations of the Olfactory Mucosa in Postnatally Developing Rabbits

“…However, regarding postnatal development in this species, relatively little is known particularly regarding how the OM structurally adapts to the unusually high olfactory functional demands. Modification in structure of the nasal olfactory tissue during juvenile development would be essential as a preparative measure for a selfdependent adult life in regard to olfactory functional needs (Schluessel et al, 2010;Kavoi et al, 2010). This is particularly critical in the rabbit where the young are abruptly weaned at about day 26 in preparation for the next litter and have to typically make the transition to independent feeding without the direct behavioral assistance of their mother (Hudson and Altb€ acker, 1994;Hudson et al, 1996).…”