The seven-band grouper, Epinephelus septemfasciatus (Thunberg), is currently recognized as a potential new species for aquaculture in Japan. This study describes normal and abnormal skeletal development of the jaw and vertebrae in cultured larvae and early juveniles of E. septemfasciatus. The ontogenetic stages at which skeletal deformities of jaw and vertebra developed were also described for this species. Osteological observations were made using a clearing and staining method for larvae and soft X-ray photographs for juveniles. A high incidence of skeletal deformities was observed in the jaws and vertebral column during the larval and juvenile stages. Most of the jaw deformities were explained by an abnormal maxilla curvature. Jaw deformities were visually evident from £exion stage after ossi¢cation of the deformed elements. Deformities in the vertebral column (mostly lordosis) were observed from the postlarval stage and became more evident as growth proceeded. The lordosis generally occurred on the positions of the 8^11th vertebra. These types of deformities are compared with those of other species, and possible causative factors of the skeletal deformities are discussed.

Low-carbon/medium-nitrogen 316 stainless steel (316FR) is a principal candidate for the high-temperature structural materials of a demonstration fast reactor plant. Thermo-mechanical fatigue damage is one of critical issues to be known for the design and reliability of the high-temperature materials subjected to thermal cycles. Early growth of small cracks in order of micron-meters in size can provide some essential information for life and the remaining life prediction to these failures. Thus, many efforts have been made; however, there are a lot of matters to be understood. This paper is dealing with how cracks propagate under thermo-mechanical fatigue conditions. Special attentions are paid to the roles of strain rate and thermal cycles on small crack propagation behaviors in 316FR stainless steel. The experimental results revealed a difference in crack growth rates between the small and long cracks under the creep-fatigue condition : the small cracks exhibited growth rates remarkably higher than long cracks at a given fatigue J integral range. The results also indicated that the small crack propagation rate under the isothermal low cycle fatigue increased with the decreasing of the strain rate due to creep effect. It was also shown from the results that the role of irreversible creep strain, as well as that of irreversible plastic strain, was essential in small crack propagation process under the in-phase type thermo-mechanical loading.

In this paper, the crack propagation behavior of naturally initiated small crack in in low-carbon/medium-nitrogen 316 stainless steel under thermo-mechanical fatigue loading was investigated. The experimental results indicated that the importance of the investigation of small crack propagation behavior because the information on the basis of physically long crack growth rate provides a dangerous evaluation on reliability to actual components. The small crack exhibits high growth rate under the In-phase TMF loading because of irreversible creep and plastic strains. However, the growth rates of small crack under the Out-of-phase TMF loading were lower because the effect of creep deformation became negligible in such condition.

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