linear relationship between pumping and respiratory rate suggesting 

 regulation of water transport in relation to metabolic rate. Oxygen uptake 

 was a power function of tissue weight, the exponent was 0.3561 for wet 

 weight and 0.3556 for dry weight. Weight specific respiration was a 

 function of pumping rate and decreased with increasing size of clam. 

 Oxygen deprivation resulted in an oxygen debt which was paid during first 

 hours of subsequent aerobic period in which utilization coefficient was 

 high and decreased gradually to a constant level. When external 02 was 

 reduced to critical value of 5 mg 02/liter, the clam increased efficiency 

 of oxygen removal from water. Below the critical concentrations, O2 con- 

 sumption declined continuously. 02 consumption increased with decreasing 

 salinity, indicating a euryhaline response. 02 consumption increased with 

 increasing temperature up to about 26 °C above which consumption dropped 

 rapidly. - D.L. 



761 



Hamwi, Adel. 1969. 



Oxygen consumption and pumping rate of the hard clam Mereenaria mereenaria L. 

 Ph.D. Thesis, Rutgers Univ., New Brunswick, N.J. ,185 p. 



Pumping rates were measured by replacing incurrent flow by a metered stream of 

 colored seawater, oxygen consumption polarigraphically and calculated by 

 difference between incurrent and excurrent water. Pumping rate was a function 

 of total weight, and nearly proportional to surface. At 3=25*2°/°° pumping 

 stopped below 6° and above 32°C. Between 7° and 12°C pumping increased 

 moderately. Above 18°C it increased to a maximum between 20° and 26°C, and 

 above 26°C pumping decreased abruptly. At 25±1°C pumping of non-acclimated 

 clams was completely inhibited below 15 and above 32°/oo. After acclimation 

 the upper salinity limit increased to about 36°/oo, the lower limit remained 

 unchanged. Maximum pumping rate was between 23 and 27°/°°. Pumping was more 

 sensitive to temp than to salinity change, and when the two factors were 

 interacting maximum pumping occurred in the ranges 17 to 24°C and 18 to 26°/°», 

 Pumping rate was reduced progressively with silt content, by as much as 93% 

 with 2 g silt/liter of water. Response to sudden upward changes in temp was 

 rapid. Oxygen consumption was a function of clam weight. Q02 was a function 

 of pumping rate, and decreased with increasing size of clam. Pumping rate and 

 oxygen consumption were related linearly, suggesting regulation of water 

 transport by oxygen demand. Oxygen consumption increased with temp to about 

 25°C, then dropped rapidly. Maximum O2 consumption was at 21 to 25°C and 

 21.5 to 25. 5°/° o. 02 consumption was more sensitive to salinity than to temp 

 change. Percent O2 utilized was more sensitive to salinity than to temp 

 change. With decreasing O2 concentration down to about 5 mg/liter Mereenaria 

 regulated O2 consumption by increasing efficiency of O2 withdrawal. Below 

 this value O2 consumption declined continuously. Deprived of O2 , clams 

 incurred an oxygen debt, which was paid during the first hours of the 

 subsequent aerobic period, in which utilization coefficient was high, then 

 decreased gradually to a more or less constant level. - modified from Dissert. 

 Abstr. Internatl. 1970: 3433B-3434B - J.L.M. 



762 



Hamwi,. Adel, and Harold H. Haskin. 1969. 



Oxygen consumption and pumping rates in the hard clam Mereenaria mereenaria: 

 A direct method. Science 163(3869): 823-824. 



Respiratory rate (or pumping rate) of hard clam is a direct function of 

 oxygen consumption (or vice versa) . This suggests regulation of water 

 transport by oxygen requirement rather than by feeding. This is in contrast 

 to the generally accepted idea that respiration in bivalves is only incidental 

 to water flow maintained for feeding. The method is described and the 

 apparatus illustrated. - J.L.M. 



212 



