INGESTION, ABSORPTION, AND GROWTH-RATES OF PARACENTROTUS-LIVIDUS (ECHINODERMATA, ECHINOIDEA) FED DIFFERENT MACROPHYTES

We recorded ingestion, absorption, total and gonadal growth rates of Paracentrotus lividus fed unlimited rations of 12 macrophytes (Rissoella verruculosa, Corallina elongata, Asparagopsis armata, Cystoseira mediterranea, Stypocaulon scoparium, Padina pavonica, Cystoseira compressa, Colpomenia sinuosa, Dilophus spiralis, Ulva rigida, Posidonia oceanica and Codium vermilara) over a 6 mo period. Macrophytes seemed to affect ingestion, absorption, total and gonadal growth rates. This effect was altered by changes in echinoid size and temperature during the length of the experiment. The highest ingestion, total growth and gonadal production were obtained with R. verruculosa whereas the lowest rates were obtained with A. armata and D. spiralis. There was no gonadal growth below a minimal ingestion rate of 3 g organic matter per 6 mo. Above this ingestion rate threshold, the allocation of energy between somatic and gonadal growth was not affected by the offered macrophyte. The highest absorption rates were recorded for A. armata. The lowest absorption rates were recorded for C. elongata and S. scoparium. Ingestion and absorption rates correlated negatively. Overall, individual growth rates positively correlated with rates of ingested organic matter, and even more so for the total time interval of the growth experiment, with absorbed organic matter. Individual monthly growth rates were better correlated with amounts of ingested organic matter than with ingested volume, wet weight, dry weight, or even energy, proteins and essential amino acids. Probably due to high individual variability, coefficients of determination were not significantly higher when using absorbed amounts of organic matter, dry weight, energy and proteins.