Mugiya and Oka: Biochemical relationship between otolith and somatic growth in Oncorhynchus mykiss 



241 



12 3 5 ^ ' 2 3 4 



Days aftec starvation or refeeding 



Figure 1 



Percentage effects of starvation and refeeding on in vitro 

 calcium deposition on otoliths in Oncorhynchus mykiss. Con- 

 trol values are pooled and the mean level (horizontal bar) is 

 shown with SE of 48 otoliths. Vertical bars represent mean 

 1 SE of 8-10 otoliths. Arrow indicates time when fish were 

 refed. *P<0.05. 



standard solutions were prepared using RNA from 

 yeast and DNA from salmon sperm (Wako Chem.). 



Statistics 



Student's (-test for unpaired observations was applied 

 to assess statistical significance of differences between 

 mean values. Significance was accepted at P<0.05. 



Results 



Starvation and refeeding 



The rate of in vitro calcium deposition on otoliths 

 ranged from 0.06 to 0.08^g/mg-hour in the control 

 group. These data are pooled and presented as the 

 mean level with standard errors (Fig. 1). Effects of 

 starvation and refeeding on the rate are expressed as 

 a percentage against the control level. Starvation in- 

 duced an inhibitory effect (P<0.05) on the rate of cal- 

 cium deposition on otoliths by day 2, decreasing to 

 approximately half of the control. This level remained 

 almost unchanged until day 5, the last day of starva- 

 tion. On refeeding, the starvation-induced decrease 

 recovered to the control level as early as day 1 . How- 

 ever, this recovery was transient, followed by a sig- 

 nificantly (P<0.05) reduced calcium deposition on day 

 2. This reduced calcium deposition recovered to the 

 control level on day 4 after refeeding (Fig. 1). 



pJq 



12 3 5  1 2 3 4 



Days after starvation or refeeding 



Figure 2 



Percentage effects of starvation and refeeding on RNA-DNA 

 ratios in white trunk muscle in Oncorhynchus mykiss. Con- 

 trol values are pooled and the mean level (horizontal bar) is 

 shown with SE of 26 fish. Vertical bars represent mean 1 SE 

 of 4 or 6 fish. Arrow indicates time when fish were refed. 

 *P<0.05; **P<0.01. 



Muscle RNA and DNA concentrations and their 

 ratios are presented in Table 1 and Figure 2, respec- 

 tively. Starvation and refeeding affected RNA concen- 

 trations, but DNA concentrations remained constant 

 during the experiment (Table 1). Therefore, changes 

 in RNA-DNA ratios are primarily attributable to 

 changes in RNA concentrations. 



