FURTHER STUDIES ON ALLOCENTROTUS FRAGILIS, A DEEP-SEA ECHINOID

¹ Department of Biological Sciences, Stanford University, Stanford, California

1. Additional data on the size of the gonads relative to the body and the presence and ripeness of gametes and their maturity were gathered for a year on the deep-sea echinoid, Allocentrotus fragilis.

2. The data indicate that the breeding season is an annual cycle with a maximum gonadal size in January and February, accompanied by the presence of mature eggs and sperm.

3. The sea urchins in one collection were found to have fed on large algae, the pellets resembling those of the intertidal sea urchin, Strongylocentrotus purpuratus.

4. A considerable quantity of lipid is found to be stored in the wall of the gut, less in the gonad, and still less in the body wall (per unit dry weight). Total amount of stored lipid is largest in the gut, next in the test, and least in the gonad.

5. The usual diatom diet of the sea urchin contains much fat; the algae tested in one series contain considerably less.

6. The respiratory quotient of the gut, ovary and test of the sea urchin was found to be about 0.6 to 0.7, suggesting utilization of lipids. The R.Q. for the testis was 0.92.

7. Some comparisons are made between Allocentrotus and the purple intertidal urchin, Strongylocentrotus purpuratus.