Some Properties of Taste Receptors in Freshwater Fish: Responses to Weak Solutions

Abstract

Despite many behavioural investigations, our knowledge of the chemoreceptive functions in fish is still meager. Following a pioneering study by HOAGLAND ('33), apparently no detailed investigation on taste function in fish has been carried out until recently in spite of the obvious need for information on chemoreception in purely aquatic vertebrates. Receptors of freshwater and marine fish are constantly exposed to hypo-and hypertonic environments respectively, and thus might be expected to exhibit an excitatory mechanism which is rather different from that of land-inhabiting animals. Quite recently some properties of the taste receptors of freshwater fish were analyzed by several workers (TATEDA, '61; KONISHI & ZOTTERMAN, '61a, '61b , '63). The electrical response from the palatine nerve supplying the palatal organ in the carp, situated in the roof of the mouth and having particularly dense taste buds on its surface, was found to be ideally suited for obtaining further information about the gustatory mechanisms in freshwater fish (KONISHI & ZOTTERMAN, '61a, '61b). One of the authors (J. K.) had noticed the peculiar phenomenon that the receptors of freshwater fish are highly sensitive to very weak salt solutions such as NaC1, whereas NaCl in higher concentration produced little response, in some cases even smaller than the response to distilled water (KONISHI & ZOTTERMAN, '63). This report presents the results of further experiments that provided more detailed information on this subject. METHODS The experiments were carried out on 106 carp (Cyprinus carpio (L.)), with an average body length of 48 cm. A most important condition for success of this experiment was the use of healthy fish maintained in good condition. After the fish was decapitated, the vagal lobe and medulla oblongata were destroyed to abrogate

Water response of the frog olfactory epithelium as observed from the olfactory bulb.

“…These include the monkey (Gordon, Kitchell, Str6m & Zotterman, 1959), the pig (Zotterman, 1956), the dog (Liljestrand & Zotterman, 1954), the cat (Liljestrand & Zotterman, 1954;Cohen, Hagiwara & Zotterman, 1955), the rabbit (Zotterman, 1956), the chicken and the pigeon (Kitchell, Strom & Zotterman, 1959;Halpern, 1962). The palatal organs of the carp (Konishi & Zotterman, 1963;Konishi & Niwa, 1964;Konishi, 1966Konishi, , 1967 also produced the water response. In the pelvic fins of the tomcod and the finray of the searobin, the spontaneous nerve discharge was suppressed by water (Bardach, Fujiya & Holl, 1967).…”

Fresh-water Fish Chemoreceptors Responsive to Dilute Solutions of Electrolytes

“…The palatal chemoreceptors of the carp display a rather peculiar type of response to varying concentrations of electrolytes (Konishi and Niwa, 1964). Dilute solutions of salts, especially those with polyvalent anions such as Na 3citrate and Na 2 HP04, produced strong responses.…”

Remarkably high ingestion ratio of acidic food in juvenile marble goby, Oxyeleotris marmorata

“…Vertical bars show the 95% confidence interval of the data the TS pellets increased (pH level decreased), the amount of Cl -ion was also increased. Fish intraoral taste system can be sensitive to the Cl -ion as examined electro-physiologically (Konishi and Niwa 1964). Therefore, the high ingestion ratio of the highly acidic TS pellets in the present study also could be contributed by the Cl -ion.…”