The histological structure and development of spines on the skin surface of Takifugu obscurus were studied during larval development conducted artificially with an average 30& salinity and 18.0-20.3°C water temperature. The epidermis comprises an outermost layer, middle layer, and the stratum germinativum, and contains three types of gland cells: small spherical or flask-shaped mucous cells, larger sacciform mucous cells, and large granular cells. The dermis and subcutis follow. The spines first appear over the ventral region at 10 days after hatching and consist of two parts: a central long tapering portion which projects into the epidermis and eventually outside of the body, and a short supporting basal portion that is embedded within the stratum compactum layer of the dermis. The central, long tapering portion has two very short processes on top until 25 days after hatching, but these two separate spines fuse into one 30 days after hatching. In contrast, the short supporting spines rooted at the base consist of three to six small spines (usually four to five spines) and are present even in the adult stage. Therefore, calcareous spines consisting of one central long spine and three to six smaller supporting spines form tetra-and septaradiate spines (mainly penta-and hexaradiate). The spines first appear over the ventral region.

In this study, defect formation mechanisms in the ERW (electric resistance welding) process for API pipe production were investigated. The results showed that defects observed in the weld joint of ERW pipe are a main factor in the deterioration of the mechanical properties of welded joints. From systematical research, it was clear that the crucial main defects of ERW pipe are caused by large inclusions with complex compositions after the steel making process and penetrators formed during ERW welding with excessive heat input condition. In order to guarantee the toughness of the weld joints, after theoretical and experimental considerations ERW pipe weld defect reducing methods can be recommended. According to previous test results, it was clear that the hook cracks caused by large inclusions were reduced by selecting the slag composition ratio of CaO and Al2O3 at the eutectoid point during steel making process. On the other hand, in case of the penetrator formation type defects, it was defined that by controlling of the heat input in the optimization range was the best solution for decreasing the penetrator formation.

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Ultrastructural studies of spermatogenesis and the functions of Leydig cells and Sertoli cells were investigated by electron microscope observation. Ultrastructural characteristics of spermatozoa of Larimichthys polyactis (Sciaenidae) have a round head, a nucleus containing highly compact filamentous clusters of chromatin, slightly eccentric nuclear fossa, no acrosome, a short midpiece with a short cytoplasmic channel, and a flagellum showing the classic axoneme structure (9 '2) and short irregular flagellum lateral fins. The spermatozoon of this species (Sciaenidae) is Perciformes type II: the flagellar axis is parallel to the nucleus, the centriolar complex is outside the nuclear fossa, the proximal centriole is anterior and perpendicular to the distal centriole, and no more than five spherical mitochondria are observed. Each of the well-developed Leydig cells observed during the periods of active meiotic division and before spermiation contains an ovoid vesicular nucleus; a number of smooth endoplasmic reticulum, tubular, or vesicular mitochondrial cristae; and several lipid droplets within the cytoplasm. This indicates that Leydig cells, as typical steroidogenic cells showing several cytoplasmic characteristics, are involved in male steroidogenesis. However, no clear evidence of steroidogenesis or of any transfer of nutrients from the cells to spermatids that appears to be associated with phagocytic function in the seminiferous lobule was observed for Sertoli cells. These findings indicate that Sertoli cells of this species function in phagocytosis and the resorption of products originating from degenerating spermatids and spermatozoa following spermiation.

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