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This study investigated the in vivo and in vitro effects of Rhizopus (filamentous fungus) extract (RU) in masu salmon Oncorhynchus masou Brevoort. Underyearling fish were fed with RU for 16 months. Monthly changes in body growth, gonadal maturation and serum levels of sex steroids were monitored. Gonads were also incubated at 0, 1, 10, 100 and 1000 μg RU mL−1 Leibovitz's L‐15 medium for 18 h. The levels of steroids in serum and cultured medium were measured. It was determined that RU‐fed immature and mature males, when compared with control groups, showed significantly higher body growth during spring, summer and the spawning period. Similarly, immature RU‐fed females showed significantly higher fork length and body weight in autumn, spring and summer. Furthermore, RU‐fed males showed significantly higher levels of serum testosterone (T) and 11‐ketotestosterone (11‐KT) levels in the pre‐spawning season, and 17α, 20β‐dihydroxy‐4‐pregnen‐3‐one (DHP) in the spawning season. In vitro RU incubation of gonads showed a dose‐dependent and significant increase in T, 11‐KT, oestradiol‐17β and DHP release in the medium. It appears that the causes of enhanced body growth and increased steroid production herein observed in salmonids are the physiologically active substances that may be present in the mycelium of the fungus. 相似文献
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Makiguchi Y Konno Y Konishi K Miyoshi K Sakashita T Nii H Nakao K Ueda H 《Fish physiology and biochemistry》2011,37(2):273-284
The movements of 28 adult chum salmon, Oncorhynchus keta (Walbaum) tagged with electromyogram (EMG) transmitters were tracked along the Toyohira river, Hokkaido, Japan, in October
of 2007 and 2008 to investigate and evaluate the upstream migratory behavior through the protection bed and fishway of ground
sills. The approach time of fish that ascended successfully through the protection bed and fishway was shorter than that of
unsuccessful fish. The unsuccessful fish were observed to swim in currents with high water velocity and shallow water depth
at swimming speeds that exceeded their critical swimming speed (U
crit) during the approach to these structures. In consequence, unsuccessful fish frequently alternated between burst and maximum
sustained speeds without ever ascending the fishway, and eventually became exhausted. It is important that fishway are constructed
to enable chum salmon to find a passage way easily, so that they can migrate upstream rapidly without wasting excessive energy. 相似文献
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