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Sakhalin taimen, Hucho perryi, is one of the largest freshwater fish in Japan, where it is close to extinction because of indiscriminate fishing, water pollution, and river construction. Interpretable ecological information about the species, however, is scarce. We examined the migration history of H. perryi by analysis of strontium (Sr) content in fish scales using inductively coupled plasma mass spectrometry and Sr distributions associated with ridges (growth lines) in the scales, with micro-beam scanning PIXE (micro-PIXE) analyses. Sr levels in the scales of H. perryi collected along the Sarufutsu coast were higher than those of salmonid collected at Shumarinai, a freshwater lake. Micro-PIXE line analyses showed that the scale Sr values of the Shumarinai Lake samples remained consistently low from the edge toward the core of the scales. The Sr values from the Sarufutsu coast samples remained relatively high from the edge toward the core; Sr levels from second to fourth position from the edge were about ten times higher than the mean levels of Shumarinai Lake samples. These results suggested that H. perryi from the Sarufutsu Coast had experienced the marine environment.

Strontium (Sr) concentration in the shells of short-necked clams collected at different locations (Shirahama, warm area and Maizuru, cold area, Japan) was analyzed by two methods, PIXE and EPMA. The Sr concentration of external surface of shell umbo, which was made during short term at early benthic phase, was analyzed by PIXE, and was ranged from 1000 to 3500 ppm for individuals. The Sr concentration of clams collected at Shirahama showed positive correlation with shell length (SL) in individuals with SL <31mm, whereas clams collected at Maizuru did not show significant correlation. This result may be caused from the difference of the spawning seasons between two areas. The Sr concentration of cross section of shell umbo, which develops thicker continuously during their life to form faint stratum structure, was analyzed by EPMA along the line across the stratum structure. Some surges and long term waving patterns of the Sr concentration were observed. These results suggest that the life histories of individual clams could be recorded in the shell umbo cross sections as variations of trace elements and analyses of trace elements could clarify the histories of individual clams.

Trade-offs among life-history traits are often thought to constrain the evolution of populations. Here we report the disappearance of a trade-off between early fecundity on the one hand, and late-life fecundity, starvation resistance, and longevity on the other, over 10 yr of laboratory selection for late-life reproduction. Whereas the selected populations showed an initial depression in early-life fecundity, they later converged upon the controls and then surpassed them. The evolutionary loss of the trade-off among life-history traits is considered attributable to the following factors: (1) the existence of differences in the culture regimes of the short- and long-generation populations other than the demographic differences deliberately imposed; (2) adaptation of one or both of these sets of populations to the unique aspects of their culture regimes; (3) the existence of an among-environment trade-off in the expression of early fecundity in the two culture regimes, as reflected in assays that mimic those regimes. The trade-off between early and late-life reproductive success, as manifest among divergently selected populations, is apparent or not depending on the assay environment. This demonstration that strong genotype-by-environment interactions can obscure a fundamental trade-off points to the importance of controlling all aspects of the culture regime of experimental populations and the difficulty of doing so even in the laboratory.

Drosophila melanogaster populations that exhibit constrasting life histories as a result of laboratory selection were compared at several potentially relevant enzyme loci. Selection regimes included postponed reproduction, accelerated development, and intermediate generation time. Each selection regime was represented by fivefold replicated populations maintained for between 50 and 500 generations. For each population, allele frequencies were calculated from frequencies of electrophoretically distinguishable allozymes of alcohol dehydrogenase, α-glycerol-3-phosphate dehydrogenase, phosphoglucomutase, and CuZn-superoxide dismutase. Based on allozyme frequency changes consistent across replicate populations, two of the studied loci responded to both selection for postponed reproduction and selection for accelerated development. The responses to contrasting selection regimes were in opposing directions, suggesting antagonistic pleiotropy.