Acid Tolerance of Japanese Dace (a Cyprinid Teleost) in Lake Osorezan, a Remarkable Acid Lake(Physiology)

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The Japanese dace (Tribolodon hakonensis) is the only teleost species that inhabits Lake Osorezan, a remarkable acid lake in Japan with the water pH of 3.4-3.8. In the present study, physiological changes following transfer of the dace acclimated to neutral stream water (pH 6.8-7.2) to acid lake water (pH 3.6-3.7) were examined with special reference to changes in gill chloride cell morphology. The dace survived direct transfer to acid lake water for 3 days. Plasma [Na^+] and [Cl^-] showed transient decreases at 1 hr after transfer ; however, the decrease in [Na^+] was greater than that in [Cl^-]. The recovery of [Cl^-] was more evident than that of [Na^+]. The transient decreases of plasma [Na^+] and [Cl^-] were followed by acidosis. Blood pH was decreased by 0.13 unit at 6 hr, but partially restored by 24 hr. In the dace acclimated to neutral stream water, chloride cells were scattered in the gill filament. Following transfer to acid lake water, however, well-developed chloride cells were arranged in a radial fashion, forming follicular or gland-like structures in the gills. Each chloride cell was equipped with an apical pit, which faced a common lumen leading to the external environment. These findings provide morphological evidence for a significant role(s) of gill chloride cells in ion and acid-base regulation in the acid-tolerant dace.
社団法人日本動物学会の論文
1999-12-15