THE SIZE AND SHAPE OF METAMORPHOSING LARVAE OF VENUS (MERCENARIA) MERCENARIA GROWN AT DIFFERENT TEMPERATURES

¹ U. S. Fish and Wildlife Service, Bureau of Commercial Fisheries, Biological Laboratory, Milford, Connecticut

1. The mean setting dates for larvae of Venus (Mercenaria) mercenaria grown at constant temperatures of 30.0°, 27.0°, 24.0°, 21.0° and 18.0° C. were found to lie on an almost perfectly straight line according to equation Y' = - 1.00 X + 37.91, where Y' is the predicted setting date and X is the temperature.

2. There were no significant differences among the five temperature groups with respect to mean length of larvae at time of setting.

3. There was no apparent relationship between maximum length of larvae at time of setting and temperature.

4. The correlation between mean width and mean length of larvae at time of setting was very high (r = .95).

5. No apparent relationship was found between shape of larvae (i.e., ratio of mean length to mean width) at time of setting and temperature.

6. The average daily growth increment for all cultures at given temperatures under the conditions prevailing during the experiments was determined.

7. The rate of growth of larvae of the southern clam, Venus (Mercenaria) campechiensis, was the same as that of the northern species, Venus (Mercenaria) mercenaria, when the temperature and other conditions were identical. Moreover, setting of larvae of both species began at the same time.