THE MORPHOLOGY OF THE OLFACTORY ORGAN OF HOPLOPAGRUS GUENTHERI GILL 1862

Abstract

The olfactory organ of Hoplopagrus guentheri Gill 1862, (Family Lutjanidae) was examined in 11 fish ranging from 63 to 480 mm in body length. Detailed measurements showed that the growth of the olfactory epithelium occurs by increase in both size and number of olfactory lamellae. A 63-mm fish had 36 lamellae, each approximately 1 mm². A 480-mm fish had 230 lamellae, each about 11 mm². Water is drawn into the nose through the anterior opening by a large lacrimal sac. A valve in the posterior opening prevents entrance of water, but allows the water to flow out. The olfactory organ of Hoplopagrus is extremely well developed. The number of folds (230 in one nose) and the size of the olfactory epithelium (up to 2450 mm²) are much greater than have been reported for any other fish. It is suggested that Hoplopagrus is, unlike most Sparidae, nocturnal and that this specialized olfactory organ is of biological importance in life at low light intensities.