SCANNING ELECTRON-MICROSCOPIC OBSERVATIONS OF THE CHEMORECEPTORS AND MECHANORECEPTORS OF CARP LARVAE (CYPRINUS-CARPIO) AND THEIR RELATIONSHIP TO EARLY BEHAVIOR

Scanning electron microscopic observation of embryos and larvae of the carp (Cyprinus carpio) in the course of development was undertaken to further understanding of the relationship between larval behaviour an d their chemo- and mechanoreceptors. Free neuromasts and olfactory pit s equipped with mechano- and sensory-cilia were found on carp embryos. During larval development, the number of neuromasts and the olfactory mechano- and sensory cilia steadily increases and they become more mo rphologically differentiated. The olfactory features, presented in ear ly larval stages, indicate that although the olfactory organ at this e arly life history has not yet attained its final configuration, it can perceive odour stimulation. The neuromasts found on the forehead of t he newly hatched larvae seem to assist in the early behavioural select ion, approach and attachment to a substratum, before the stage of fill ing of the gas bladder. The increasing number of neuromasts during dev elopment reflects the larvae's capability of capturing food items in t he absence of visual stimulation. The rapid maturation of free neuroma sts, the lateral-line system and the olfactory organ, is evidence of t heir post-metamorphosis position in the search for, location and succe ssful capture of food.