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Two subtypes of insulin-like growth factor binding protein (IGFBP)-1 are present in salmon blood and they are both up-regulated under catabolic conditions such as stress. The present study examined effects of fasting and re-feeding on IGFBP-1a (28-kDa form) and IGFBP-1b (22-kDa form) both at mRNA and protein levels along with IGF-I and RNA/DNA ratio in yearling masu salmon. Fish were individually tagged and assigned to one of three treatments: Fed, Fasted or Re-fed. Circulating IGF-I levels significantly decreased after fasting for 5 weeks and were positively correlated with individual growth rates. Liver igf-1 mRNA levels were not affected by the treatment. Muscle RNA/DNA ratio did not respond to fasting nor showed correlations with growth rates. Circulating IGFBP-1a and IGFBP-1b increased during fasting and decreased after re-feeding. Both serum levels were inversely correlated with growth rates, while IGFBP-1b had consistent negative relationships with growth rates. Fasting/re-feeding also affected their mRNA levels in the liver. These results suggest that circulating IGF-I and IGFBP-1b could serve as positive and negative indices of growth, respectively, in masu salmon. Different sensitivities of IGBP-1a and IGFBP-1b may be useful to assess a broad range of catabolic conditions when they are combined.

Although tetraploidy is considered to be important and useful for the production of sterile triploids and fertile allotetraploids in aquaculture, in most cases the resultant embryos exhibit extremely low survival. In this study, we aimed to clarify the cause of the inviability of tetraploids in masu salmon. Firstly, we compared developmental rates of the first cell cycle among 9 single pairs produced by all possible matings between 3 females and 3 males. The results showed that the fertilized eggs developed almost synchronized among individuals from each pair but asynchronous among pairs and this asynchronous development was more apparent among pairs from different female than those from different male. Secondly, we induced both tetraploidy (4N) and gynogenetic diploidy (G2N) by the same hydrostatic pressure shock (PS) conditions (700 kg/cm 2, 7 min duration) for the first cleavage inhibition using single-pair mating. This experiment was designed to verify whether the cause of mortality of induced tetraploidy was the elevated ploidy itself. Eggs from one female were divided into 2 groups and fertilized with normal or UV-irradiated sperm from one male, respectively. Then each group of eggs was subdivided into 6 groups: one was an intact control and the other 5 groups were treated with PS at every 30 min from 5 to 7 hpf at 10 °C. As a result, the treated eggs of 4N and G2N showed the highest survival (90.8% and 60.6%, respectively) and embryogenesis rate (both 100% relative to surviving eggs) at 33 dpf, only when PS treatment was performed at late prometaphase (6 hpf and 6.5 hpf, respectively). The other PS groups showed extremely low survival (1.5-52.8% and 3.1-14.8%), ceased morphogenetic development and developed into only undifferentiated cell masses. This experiment was repeated 2 more times using other single-pair mating and the results showed the same tendency. The embryonic bodies were confirmed by flow cytometry to have approximately objective ploidy, tetrapl, http://www.sciencedirect.com/science/journal/00448486