Nutrient Translocation during Early Disc Regeneration in the Brittlestar Microphiopholis gracillima (Stimpson)...

Microphiopholis gracillima can autotomize and then regenerate the autotomized central disc, including integument, gut, and gonads. Experiments were carried out to determine the relative importance of internal nutrient reserve translocation and exogenous nutrient uptake during the regeneration process. Approximately 60% of the dry body weight of M. gracillima is organic material. Intact animals held for three weeks in natural seawater did not change significantly in weight, caloric content, or relative concentration of protein, carbohydrates, or lipids. Intact animals held for three weeks in artificial seawater devoid of nutrients lost weight and caloric content. The rate of loss was rapid initially, but slowed after about eight days. Animals regenerated in natural seawater lost weight initially, then regained the lost weight. Animals regenerated in artificial seawater lost weight constantly and at a higher rate than either the artificial seawater control or natural seawater regenerated animals. All weight losses were attributable to significant changes in the protein and carbohydrate fractions of the organic body component. The lipid fraction and ash components did not change significantly in any treatment. M. gracillima appears to be adapted to regenerate the lost disk rapidly, even under conditions of food deprivation.