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

The rates of ingestion, egestion, ammonium excretion, and CO2 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 tilt three macrophytes (Sagassum 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 CO2 respiration rates (r(2)=0.92) and ammonium excretion rates (r(2)=0.86). Weight-specific egestion rates, CO2 respiration and ammonium excretion were indirectly proportional to body weight. For weight-specific egestion rate (in mug DW facces/g DW urchin-h) the regression coefficient, b and constant, K were -2.31 +/-0.68 (mcan +/-SE) (P=0.02) and 6359.55 +/-5394.31 (P=0.29), respectively. The b and K for CO2 respiration were -1.28 +/-0.48 (P=0.0.1) and 39.72 +/-10.59 (P=0.01), respectively. For ammonium excretion, the h and K were -1.03 :1:+/-0.46 (P=0.11) and 262.51 +/-56.89 (P=0.02), respectively.