Biochemical changes during reproduction and starvation in the sipunculid worm Phascolosoma agassizii

Abstract

1. 1. Levels (% dry weight) of protein, non-protein nitrogen, total carbohydrate, glycogen, lipid and lipid fractions, and water were determined for Phascolosoma, some of them at various times in the reproductive cycle, and after various degrees of starvation. 2. 2. The body of the worm contains about 82·3 per cent water; various tissues contain 75–78 per cent water. The water content of a starved worm increases to between 86·2 and 88·3 per cent. 3. 3. The protein tissue (Kjeldahl) level is about 30 per cent; lipid levels vary for different tissues, being 25 per cent in the gut, 17·2 per cent for eggs, 6·9 per cent for sperms, and lesser quantities in muscle and body wall. However, the lipid level of the female body wall is double that of the male. About half of the lipid content of the female worm is in the eggs. 4. 4. Starvation results in a weight loss accompanied by a decrease in lipid reserves, particularly of the neutral lipid. Later the protein content also decreases. GLycogen levels are maintained or may even rise during starvation, although glycogen content may decline. Non-protein nitrogen levels rise during utilization of protein. 5. 5. The respiratory rate of Phascolosoma is of the order found in other marine invertebrates. Calculations based on oxygen consumption show that a Phascolosoma rapidly exhausts its nutrient reserves.