Testicular development and serum profiles of steroid hormone levels in captive male Pacific herring Clupea pallasii during their first maturational cycle

The present study investigates the relationship between testicular development and serum steroid hormone levels in captive Pacific herring Clupea pallasii during the first reproductive cycle. The maturity of the testis was divided into five periods based on histological observation. These are early spermatogenic stage (April to July), mid-spermatogenic stage (August to November), late spermatogenic stage (December to March), functional maturation stage (early April) and spent stage (late April). The pattern of seasonal change in gonadosomatic index (GSI) clearly reflected testicular maturity. 11-Ketotestosterone (11-KT) levels increased from October to a peak level (6.58 ± 1.87 ng/mL) in January, and were maintained at this level until March. In contrast, testosterone levels were consistently low, less than 1 ng/mL, at all times. These results suggest that 11-KT is the predominant androgen that controls spermatogenesis in this species. 17,20β-Dihydroxy-4-pregnen-3-one (DHP) showed a single sharp peak (3.38 ± 0.35 ng/mL) in early April of the second year, suggesting that milt production is induced by DHP as in some other teleost species.     

Adsorption of minerals on the isolated mantle of Patinopecten yessoensis

The isolated mantle of scallop ( Patinopecten yessoensis ) was shown to adsorb minerals (Zn, Ca, Mg, Fe, Cu, Ni and Co) to more than 1% upon treatment with mineral solution. The amounts of adsorbed Zn, Ca and Mg were 44.3, 47.4 and 15.5 mg/g dry weight, when the mantle was treated with 5% ZnSO₄, CaCl₂ and MgSO₄ solutions at room temperature, respectively. The amounts of adsorbed Zn, Ca and Mg were dependent on the concentration of mineral solution used. This is the first report showing that the isolated mantle adsorbs nutritionally important minerals such as Ca, Mg and Fe. This finding may lead to the development of new mineral-enriched food supplements.