Volume regulation in a euryhaline oligochaete,Pontodrilus bermudensis Beddard
Experimental data on weight/volume and water regulatory capacity of a littoral oligochaete,Pontodrilus bermudensis Beddard are presented. The results presented are of the weight/volume and water regulatory capacities under heterosmotic media ranging from 5 to 30‰ for a period of 72 h or more. The magnitude of the increase in weight is inversely proportional to the external medium concentration. The final weights attained are higher in lower salinities and lower in higher salinities. The weight/volume regulatory capacities of the worm are comparable to those reported in a number of brackish/estuarine polychaetes.
The changes in water content under heterosmotic media support the findings of its weight/volume regulatory capacities. The worm showed a narrow range of variation in percentage body water content under heterosmotic media from 5 to 30‰ The regression slope for water content change compares favourably with those reported in some polychaetes.