The influence of diet on the growth and bioenergetics of the tropical sea urchin, Tripneustes ventricosus, Lamarck

G. R. Lilly
1975
Marine plants are known to vary greatly in their growth-supporting value to sea urchins, but the reasons for the differences in growth-supporting value are not well understood. The major purpose of this study was to determine how well the tropical sea urchin, Tripneustes ventricosus, could use for growth five of the plants available in its habitat, and to determine the causes of any differences in growth by measuring simultaneously the following three phases of the food conversion process: (1)
more » ... rsion process: (1) consumption, (2) digestion and absorption, and (3) conversion of the absorbed food to growth. The foods varied in growth-supporting value as follows: Sargassum > Padina > Dictyota > Ulva >> Thalassia. Reasons for these differences were found in each of the three phases of the food conversion process: (1) Consumption rates, expressed in calories/day, varied with diet as follows: Thalassia > Sargassum > Padina > Dictyota > Ulva. This variability is attributable primarily to differences in the urchin's ability to manipulate and ingest the foods, and to differences in water and ash contents of the foods. There is no evidence that any of the foods are distasteful to the urchin. (2) Average absorption efficiencies, measured in terms of calories, varied with diet as follows: Ulva (62%), Padina (58%), Dictyota (49%), Sargassum (40%), Thalassia (23%). The natural foods of sea urchins are usually low in protein, but T. ventricosus improved the calorie : protein ratio by selectively absorbing protein from most foods. (3) Average net growth efficiencies, measured in terms of calories, varied with diet as follows: for small urchins, Sargassum (23%), Dictyota (19%), Padina (18%), Ulva (16%), Thalassia (7%); for larger urchins, Sargassum (15%), Thaiassia (3%) . When the urchin ate a given food, the net growth efficiency increased with the rate of absorption. Average net growth efficiencies, measured in terms of protein, were much higher than corresponding efficiencies measured in terms of calori [...]
doi:10.14288/1.0093587 fatcat:ltk3mquftzaatddq63tcwji2zi