MINERAL REGENERATION BY SERPULID POLYCHAETE WORMS

¹ Department of Zoology, Duke University, Durham, N. C. 27706

1. The tubes of H. brachyacantha and E. dianthus contained two polymorphs of calcium carbonate, high magnesium calcite and aragonite, whereas the mineral regenerate produced by both species contained only aragonite. The site of initial appearance of the mineral regenerate over the openings of the calcium-secreting glands and the presence of aragonite in the duct of the calcium-secreting gland of E. dianthus indicate that the aragonite of the mineral regenerate and probably also of the tube is secreted by the calcium-secreting glands. The high magnesium calcite fraction of the tube is probably secreted by the ventral shield epithelium.

2. At all salinities in which worms were able to produce mineral regenerate the rate of mineral regenerate production was extremely variable.

3. Both species of serpulids failed to produce mineral regenerate below a salinity of about 20. Above this salinity the rate of mineral regenerate production increased with increasing salinity and environmental calcium concentration. However, there was not a significant increase in the rate of mineral production by E. dianthus between normal sea water (34%, 0.430 mg Ca/ml) and hypercalcium sea water (0.490 mg Ca/ml).

4. E. dianthus, weighing about 4 mg, secreted up to 50 µg of CaCO₃ per day. Thus worms of this size secreted an amount of aragonite equivalent to about of the cell volume of the calcium-secreting glands per hour.

5. There was an inverse exponential relationship between the size of worms and both the relative rate of mineral regenerate production and the concentration of calcium in the tissues of the worms, strongly suggesting that the mass of the tissues involved in mineral production did not increase in proportion to the increase in mass of the worm.