Metabolic characteristics of sea cucumber Apostichopus japonicus (Selenka) during aestivation

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, 148.5 ± 15.4 g, medium 69.3 ± 6.9 g) and immature (small, 21.2 ± 4.7 g) individuals aestivated at water temperatures of 20 and 25 °C, respectively. The metabolic characteristics of mature individuals were different from immature individuals during this period. The OCR of mature sea cucumbers peaked at 20 °C, 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 °C, while that of the immature animals peaked at 25 °C. 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 °C, 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 °C, 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.