Visualization of skeletal structure in Sakhalin taimen, Hucho perryi, using in vivo three-dimensional micro X-ray computed tomography

Visualization of skeletal structure was examined in Sakhalin taimen (Hucho perryi) larva using in vivo three-dimensional micro X-ray computed tomography (3D micro X-ray CT) imaging. Clear 3D images of not only the vertebra, pleural rib, and otolith but also non-skeletal tissues, such as eye, gill, and alimentary canal were obtained. Deformation of caudal fin in the larva was also observed. These images provided precise morphological characteristics of Hucho perryi. 3D micro X-ray CT, therefore, would be a useful technique to investigate fish physiology and behavior research regarding fish growth and life history

MERCURY DISTRIBUTION BY MICRO PIXE ANALYSIS IN STENOPSYCHE MARMORATA EXPOSED TO MERCURIC CHLORIDE

Aquatic insects, such as caddisflies, are used as reference organisms for water pollution. The precise distribution of contaminated metals in the insect, however, remains unknown. In this study, we used micro PIXE analysis to examine mercury distribution in Stenopsyche marmorata, a typical caddisfly, exposed to mercuric chloride. The mercury level in the caddisflies after exposure to mercuric chloride at 1 mg/L for 5 days was 93.3 +- 25.0 ug/g wet weight. Micro PIXE analysis also revealed a site-specific distribution of mercury in the insects. Mercury was high in the digestive tract, where it was localized in the basement membrane and the peritrophic membrane. Mercury was also detected in the tissue surrounding the digestive tract. Further examination of the tissue identified mercury in the fat body but not in the silk gland

APPLICATION OF MICRO-PIXE ANALYSIS FOR A MIGRATION HISTORY STUDY OF HUCHO PERRYI FOCUSED ON STRONTIUM DISTRIBUTION IN FISH SCALES

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