871 



Hopkins, Hoyt S. 1946. 



The influence of season, concentration of seawater and environmental 

 temperature upon the oxygen consumption of tissues in Venus mereenaria. 

 J. Exp. Zool. 102(2): 143-158. 



Tissues of young hard clam have a higher rate of respiration than those of 

 older clams. Adductor muscle had the lowest rate, but also had the greatest 

 average difference in O2 consumption between old and young. Gill tissue had 

 the highest rate of consumption, and mantle intermediate. For gill tissue the 

 difference in rate between old and young clams is distinctly less in winter 

 than in summer. The seasonal difference in muscle tissue is small. 

 Alterations in salinity, pH, and temp of seawater produced absolute changes 

 in rate of respiration of gill tissue, without affecting relative age 

 difference much. The same was true for temperature and muscle tissue. 

 Moderate fasting in summer by clams of different ages abolished the age 

 difference for gill tissue. Increase in respiratory rate in summer of young 

 clams over old was apparently related to increase in ciliary activity, which 

 may be controlled by hormones. Excised gill tissue from N.C. clams had a 

 lower respiratory rate than that of N.Y. clams when both were held at 25°C. 

 N.C. clams at 25°C had a lower respiratory rate than N.Y. clams at 20°C. 

 - J.L.M. 



872 



Hopkins, Hoyt S. 1949. 



Metabolic reactions of clams' tissues to change in salinity. I. Ciliary 

 activity, narcotic and cyanide effects, and respiratory quotient. Physiol. 

 Zool. 22(4) : 295-308. 



Rate of O2 consumption of Venus mereenaria gill tissue was inversely 

 proportional to seawater density between 1.012 and 1.030 for clams living 

 in seawater of density 1.024. Rate of respiration in seawater 1.015 was 

 more than 4 0% higher for gill and 12% higher for mantle tissue than in 

 density 1.025. It was 15% lower for muscle sections. Ciliary activity in 

 seawater diluted to 60% did not increase activity of frontal cilia, although 

 it augmented gill respiration. Ciliary activity actually was definitely 

 lowered as compared with that in natural seawater, so that ciliary activity 

 can be eliminated as a factor in increased respiration. Isotonic NaCl 

 solution increased O2 consumption of gill tissue by 47%. This was largely 

 suppressed when CaCl2 was present in the same concentration as in seawater. 

 In a 3:2 or 1:1 mixture of isotonic NaCl with seawater there was no increase 

 in respiratory rate. M/1,000 cyanide had no effect on O2 consumption of gill 

 in summer, but produced moderate inhibition in fall, about 6 0% in mantle and 

 muscle tissues. Augmented respiration of gill and mantle in diluted sea- 

 water was inhibited relatively more by cyanide than in natural seawater. 

 Average respiratory quotient of gill was 0.87 in seawater of density 1.025, 

 and 0.94 in 1.015. It is probable that V. mereenaria has more power of 

 osmotic regulation than other species. This may be reflected in respiratory 

 responses of certain excised tissues in dilute seawater. - J.L.M. 



873 



Hopkins, Sewell H. 1956. 



Odostomia impressa parasitizing southern oysters. Science 124(3223): 628-629. 



Mereenaria mereenaria, placed in aquaria with Odostomia impressa and oysters, 

 did not attract the snails as oysters do. A few snails may crawl up on 

 quahogs but did not stay long. - J.L.M. 



244 



