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Three species of the callianassid genus Nihonotrypaea occur in the Ariake Sound estuarine system, southern Japan; they consist of two tidal-flat species (N. harmandi; N. japonica) and one boulder-beach species (N. petalura), with maximum population densities of 1440, 343, and 12 ind m−2, respectively. Nihonotrypaea harmandi and N. petalura are distributed along the coastline from the outermost part of the sound to the open sea, while N. japonica occurs in the middle part of the sound. Nihonotrypaea japonica has an extended reproductive period from late winter to autumn, while those of the other species are from late spring or summer to autumn. Interspecific comparisons were made for recently laid egg size (as volume) and clutch size (as number of eggs per female). Only in N. japonica was a seasonal egg size variation observed, being significantly larger in winter to spring (mean=0.106 mm3) than in summer (0.080 mm3). By contrast, clutch size was significantly smaller in winter to spring, resulting in nearly the same clutch volume per female (product of the mean egg volume and clutch size) between the seasons. Among the three species, the egg size was ordered as N. japonica (overall mean volume through the seasons=0.092 mm3)>>N. petalura (0.057 mm3)>N. harmandi (0.054 mm3). The clutch size was ordered as N. harmandi>N. petalura≈N. japonica. The clutch volume was ordered as N. japonica≈N. harmandi>N. petalura. The smallest clutch volume value for N. petalura female showed an opposite trend to the relative size of the major cheliped found in a previous study.

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The discoloration of yellowtail dark muscle begins at the boundary part between dark muscle and ordinary muscle, and progresses toward the body surface side. To gain a deeper understanding of this phenomenon, we examined the processes of glycolysis and lipid oxidation in the two types of muscle. The glycolysis analyses indicated that an increase of lactic acid and decline of pH occurred at the boundary between dark muscle and ordinary muscle. An in vitro experiment using dark muscle extract showed that the decline of pH promoted the oxidation of myoglobin. An in vitro experiment using a mixture of extracted lipid and myoglobin from the dark muscle showed that the oxidation of phospholipid promoted the oxidation of myoglobin. Thus, we conclude that the discoloration, caused by the decline of pH at the boundary between dark muscle and ordinary muscle, progresses toward the body surface with oxidation of the phospholipid.

We aimed to develop equipment to estimate the fat content of raw yellowtail and horse mackerel by nondestructive measurement using impedance (electrical resistance). The frequencies used were 5, 20, 50, and 100 kHz.Impedance varied with storage time after killing of theˆsh sample in all measurements using any of these four frequencies, but the impedance measured at 100 kHz showed a higher correlation with the fat content. Impedance varied with the change inˆsh body temperature. The accuracy of estimating fat content was improved by changing the electrode width to match theˆsh size. Therefore, we consider that to have better estimation of the fat content, to unify theˆsh body temperature and storage time and to use an appropriate electrode width corresponding to theˆsh size on the measurement of the impedance is eŠective.

No abstract

We investigated the in‰uence of diet and season on the discoloration of dark muscle of cultured yellowtail Seriola quinqueradiata. The amount of a-tocopherol (aToc) and ascorbic acid (AsA) in the diet aŠected the amount in dark muscle and discoloration was inhibited by the amount of AsA rather than the amount of aToc. Discoloration was suppressed by adding ascorbic acid derivatives to the diet. Discoloration varied depending on the season: the ratio of metmyoglobin to total myoglobin (metMb) was lower from August to October that than from December to March. The amount of AsA from December to March was low, and the pH of dark muscle from August to October was high. Although metMb was correlated with AsA content and pH, there was no correlation with aToc amount. Therefore, the amount of AsA and suppression of pH decrease were considered to be the key to suppressing discoloration.

We have developed a new type of heat-inducedˆsh meat gel with sodium citrate instead of sodium chloride.The eŠects of this new heat-inducedˆsh meat gel on blood pressure and lipid concentrations were investigated in rats. The new type and general type of lyophilized heat-inducedˆsh meat gels were added to control diets pre-