Feeding, respiration, and excretion by the tropical sea urchin <i>Tripneustes gratilla</i> (Echinodermata: Echinoidea) from the Philippines

Abstract

The rates of ingestion, egestion, ammonium excretion, and CO 2 respiration of Tripneustes gratilla (Echinodermata: Echinoidea) from a shallow water embayment at eastern Mactan Island, central Philippines were examined. There was no significant difference in weight-specific feeding rate with the three macrophytes ( Sargassum polycystum , Thalassia hemprichii , and Kappaphycus alvarezii ). The power function equation, M=KWb fitted well with the weight-specific egestion rates (( r 2 =0·93), weight-specific CO 2 respiration rates ( r 2 =0·92) and ammonium excretion rates ( r 2 =0·86). Weight-specific egestion rates, CO 2 respiration and ammonium excretion were indirectly proportional to body weight. For weight-specific egestion rate (in μg DW faeces/g DW urchin-h), the regression coefficient, b and constant, K were −2·31±0·68 (mean±SE) ( P =0·02) and 6359·55±5394·31 ( P =0·29), respectively. The b and K for CO 2 respiration were −1·28±0·48 ( P =0·04) and 39·72±10·59 ( P =0·01), respectively. For ammonium excretion, the b and K were −1·03±0·46 ( P =0·11) and 262·51±56·89 ( P =0·02), respectively.