Functional Morphology of the Olfactory Organs in the Spiny Dogfish (<i>Squalus acanthias</i> L.) and the Small‐spotted Catshark (<i>Scyliorhinus canicula</i> (L.))

TLDR

The olfactory epithelium of these sharks is arranged on lamellae with secondary folds and is composed mainly of microvillous receptor cells, multiciliated supporting cells, and basal cells. The study investigates the route of water current through the olfactory organ and the driving forces of ventilation. The authors examined the olfactory organs of the spiny dogfish and small‑spotted catshark using light microscopy and TEM/SEM. Only microvillous receptor cells were found, a derived character, and ventilation is driven mainly by pressure differences from active swimming in both species, with respiratory activity additionally supporting ventilation in the catshark; non‑sensory cilia play no evident role.

Abstract

Abstract The morphology of the olfactory organs in two sharks, the spiny dogfish and the small‐spotted catshark, was studied by light microscopy and electron microscopy (TEM and SEM). The olfactory epithelium is arranged on olfactory lamellae which are provided with secondary folds. The epithelium mainly consists of microvillous receptor cells, multiciliated supporting cells and basal cells. The find of only one type of receptor cells, the microvillous type, is discussed and the condition considered a derived (apomorphic) character. The route of the water current through the olfactory organ and the different driving forces of the ventilation process are subject to discussion. In both the pelagic dogfish and the bottom‐dwelling catshark the pressure difference between the incurrent and excurrent nostrils achieved by active swimming appears to be the driving force, whereas the role of the beating of the non‐sensory cilia is not evident. In the bottom‐dwelling catshark the ventilation of the olfactory organ is also supported by the respiratory activity.