Effects of salinity on ingestion, oxygen consumption and ammonium excretion rates of the sea cucumber Holothuria leucospilota

Abstract

The sea cucumber Holothuria leucospilota is a good candidate for aquaculture, for large-scale production of this sea cucumber, it is imperative to know the effects of salinity on its physiological performance. In this study, ingestion, oxygen consumption and ammonium excretion rates of the adult sea cucumber H.leucospilota (16.98 ± 1.14 g, wet weight) at various salinity levels (18, 23, 28, 33 and 38 PSU) were studied in the laboratory. The species were acclimated for 1 week at the desired salinity before testing, and were fed with sediment from their natural habitat during this period. Results showed that the minimum ingestion rate (0.02 ± 0.01 g g−1d−1) at a salinity of 18 PSU was significantly lower than those observed at salinities of 28, 33 and 38 PSU, and there was no significant difference among the values at 23, 28, 33 and 38 PSU. The maximum value of oxygen consumption rate recorded at a salinity of 28 PSU was significantly higher than the minimum at 18 PSU, no significant differences were observed among other treatments. The ammonium excretion rates of H. leucospilota also changed significantly in response to salinity variations, the maximum value observed at a salinity of 28 PSU (0.09 ± 0.03 μM g−1h−1) being nearly five times higher than the minimum value at a salinity of 38 PSU (0.02 ± 0.01 μM g−1h−1). The O:N ratio varied as a function of salinity. Lower O:N ratios (<11.0) at salinities below 23 PSU indicated protein-dominated catabolism under hyposaline stress; the higher O:N ratio (46.5) at a salinity of 38 PSU indicated carbon-based metabolism. Results of this study indicated that the sea cucumber H. leucospilota may have a wide tolerance of salinity variation. However, it is not a very suitable species for rearing in hyposaline water. This study provides useful information for improving aquaculture management in tropical and subtropical coastal areas.