Metabolic characteristics of the sea cucumber Apostichopus japonicus (Selenka) during aestivation were studied in the
laboratory. The effects of water temperature on oxygen consumption rate (OCR) and ammonia-N excretion rate (AER) in A.
japonicus were determined by the Winkler and Hypobromite methods, respectively. Mature (large, 148.5F15.4 g, medium
69.3F6.9 g) and immature (small, 21.2F4.7 g) individuals aestivated at water temperatures of 20 and 25 8C, respectively. The
metabolic characteristics of mature individuals were different from immature individuals during this period. The OCR of mature
sea cucumbers peaked at 20 8C, and then dropped significantly at higher temperatures, whereas the OCR of the immature animals
continued to increase slightly, even beyond the aestivation temperature. The AER of mature individuals peaked at 20 8C, while that
of the immature animals peaked at 25 8C. The relationships between dry weight (DW) and absolute oxygen consumption (R) and
absolute ammonia-N excretion (N) could be described by the regression equation R or N =aWb. With the exception of 15 8C, the
O/N ratios (calculated in atomic equivalents) of large size sea cucumbers was close to 20 across the temperatures used in this
study, indicating that their energy source was a combination of lipid and protein. On the other hand, apart from small individuals
maintained at 10 8C, the O /N ratios of the medium and small sea cucumbers were close to 10, indicating that protein was their
major energy source. The O/N ratios in all size groups remained unchanged after aestivation was initiated.
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