Hisaki Nakagawa

Collagen of edible jellyfish exumbrella

The edible jellyfish exumbrella collagen was prepared by limited pepsin digestion. The yield of collagen was very high; 46.4% on the basis of lyophilised dry weight. This collagen was comprised of α1α2α3-heterotrimers, moreover it was relatively stable at 26.0 °C for 60 min. Thus, the edible jellyfish exumbrella will have potential as an important collagen source for use in various industries and it is expected that the development thus so far unutilised resource will advance in the future.

Factors influencing otolith strontium/calcium ratios in Anguilla japonica elvers

The effects of temperature and salinity on the concentration ratios of strontium (Sr) to calcium (Ca) within the sagittal otoliths of elvers of the Japanese eel, Anguilla japonica, were studied by spot analysis using a wavelength dispersive X-ray electron microprobe. A total of 340 elvers were used: 100 elvers were reared for 15 days under various salinity conditions (freshwater, one-third seawater, two-thirds seawater and pure seawater at 22 °C; 240 elvers were reared for 58 days under various water temperature conditions (12, 17, 22, 27 °C) in either freshwater or pure seawater. Otolith Sr/Ca ratios were found to be positively correlated with water salinity. On the other hand, the Sr/Ca ratios were not found to be significantly different among the various temperature groups. The above results strongly suggest that the physiological mechanism of incorporation of Sr and Ca within the otolith of an eurythermal fish, Japanese eel, does not change within this range of temperatures (12–27 °C).