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This study compares the ontogenesis, morphology and cytology of olfactory organs of several species of Cichlidae (Pisces, Teleostei), from Asia, Africa and America, belonging to the subfamilies Tilapinae and Haplochrominae. Cichlids, in contrast to most other fish families, possess only one naris on each side of the nose that serves as both inlet and outlet opening. The olfactory rosettes are round, 1.8–4.2 mm diameter, and situated directly below the nares. Each rosette consists of a central raphe with attached lamellae whose number increases with age, remains constant in adults and differs in the various species. Onset of organization of the nasal organs from the neuroectoderm begins 14–16 hours after fertilization in bottomspawner cichlids, and 30–53 hours after fertilization in mouthbrooder embryos. A comparative ontogenetic study of embryos and larvae of both ethological types has shown that this difference in timing of morphogenesis also continues in the formation of the nasal pits, the development of the nasal epithelium, and the olfactory nerves. Comparative data are provided for these processes, including LM, TEM and SEM of the stereocilia and kinocilia-bearing cells, as well as of the microvillar cells. The distribution of these cell-types on the olfactory lamellae differs in the various species. The faster development of the nasal organs observed in larvae of bottomspawners as compared to mouthbrooders also matches the development of other vital organs in these two etho-types and seems to be of high adaptive value, providing the bottomspawners at an earlier stage with sensitive organs in the surrounding hostile habitats.