EFFECTS OF TURBIDITY-PRODUCING MATERIALS IN SEA WATER ON EGGS AND LARVAE OF THE CLAM (VENUS (MERCENARIA) MERCENARIA)

Open Access
Publisher Website
Google Scholar
Abstract
Quantitative determinations have been made of the effects of several concentrations of clay, Fuller''s earth, chalk and silt suspended in sea water on the development of eggs and growth of larvae of the hard clam. Some clam eggs developed normally in concentrations of clay, chalk and finely-ground Fuller''s earth as high as 4.0 g/1. The percentage developing normally decreased as the concentration of these suspended materials increased. In silt suspensions, however, there was no significant decrease in the percentage of eggs developing normally in concentrations of 0.75 g/1 or lower. The percentage decreased progressively at silt concentrations of 1.0, 1.5 and 2.0 g/1, and none of the eggs developed normally in concentrations of 3.0 or 4.0 g/1. Larvae resulting from eggs that developed to the straight hinge stage in 4.0 g/1 of clay, Fuller''s earth and chalk, and from those that developed in 2.0 g/l of silt were capable of normal growth and were reared to metamorphosis by keeping them in normal sea water after.the 1st 48 hours. Clam larvae were unable to grow in concentrations of clay, chalk or Fuller''s earch as high as those at which some eggs developed. Thus, 0.25 g/1 of chalk and 0.5 g/l of clay and Fuller''s earth were the highest concentrations of these suspended materials at which clam larvae showed any growth. At all higher concentrations of these materials the larvae showed no growth and mortality exceeded 90% within 12 days. In suspensions containing 0.75 g/1 of silt or less, larval growth was as fast, or faster, than in control cultures. Growth of larvae was progressively slower in silt concentrations of 1.0, 1.5 and 2.0 g/1, and at 3.0 or 4.0 g/1 larval growth was negligible. Even at a silt concentration of 4.0 g/1, however, there was no appreciable larval mortality within 12 days.

This publication has 0 references indexed in Scilit: