Structural and Functional Development of the Olfactory Organ in Teleosts

Abstract

Fish detect chemical stimuli through two major chemosensory channels, olfaction and gustation. All current evidence indicates that olfaction is a major mediator of chemical signals and is involved in diverse teleost behavior. This paper descnbes the morphological components and the basic principles of developmental patterns of the olfactory organ as well as cellular differentiation of receptors in rainbow trout Oncorhynchus mykiss (formerly Salmo gairdneri). The olfactory organ originates from an anlage formed by the ectoderm on the ventrolateral pan of the head during stage 19(11 d postfertilization). Ciliated receptor cells appear at stage 24 (day 18) and dominate until immature microvillar receptor cells develop in stage-28 (day 26) embryos. During this period, the olfactory placode continues a lateral and upward migration. At stage 29, the day of hatching, the olfactory groove is enclosed by flaps of skin, and by stage 33, distinct anterior and posterior nares are formed. Spontaneous electrical activity is recorded from the olfactory mucosa as early as stage 25, and neural responses to chemical stimuli are induced from stage-26 embryos that contain sparse ciliated receptor cells. Stereochemical specificity of receptor responses is evident at these stages. We conclude that the olfactory receptor has two ontogenetically distinct forms, ciliated and microvillar. By the time of hatching, both cell types are mature and capable of responding and discriminating among chemical stimuli. The functional distinction of the olfactory system is discussed further in relation to the gustatory system, which is endodermal in origin and is still incomplete at hatching. 183

Development of predator defences in fishes

“…If olfaction and taste are important senses for young fishes as prey, they must be so only for predator avoidance (not evasion), because olfactory stimuli travel slowly through water in comparison with acoustic and visual signals. Chemosensory receptors -taste buds and nasal hair cells -develop very early (Blaxter, 1988;Hara and Zielinski, 1989;Margulies, 1989;Tanaka et al, 1991). In at least some species (e.g.…”

The diversity of chemical stimulation in fish olfaction and gustation

“…wide response range, and (2) those that respond to a few amino acids, i.e. limited response range (Table 5; Hara and Zielinski, 1989;Hara, 1993b). Of 27 species whose gustatory responses to amino acids have been systematically tested, 10 species consisting primarily of channel catfish and marine species are shown to be of the wide response range.…”

“…Grouping of fish according to the specificity of gustatory responses to amino acids. Modified from Hara and Zielinski (1989) and Hara (1993b) Kiyohara et al (1975) Hidaka etal. (1985 Ishida and Hidaka (1987) L-ar~nine (L-Arg) only by two carbon chains.…”

Ontogenesis and cytomorphology of the nasal olfactory organs in the Oman Shark,Iago omanensis (Triakidae), in the Gulf of Aqaba, Red Sea

“…Most studies of this nasal sensory system have dealt with adult fish and only a very few with morphological and cytological ontogenesis from the early stages of embryogenesis (Hara and Zelinski, 1989;Zeiske et al, 1992;Fishelson, 1994). The present study of the Oman shark, Iago omanensis, follows the development of the nasal sensory organs in juveniles and its cyto-morphological structure in adults.…”