The Respiration of Some Planktonic Copepods

The respiratory rates of two neritic planktonic copepods, Centropages hamatus and Temora longicornis obtained from the northeast coast of the United States, have been shown to he very similar to the rates determined for British specimens, provided due allowance is made for the difference in size of the animals. The relationship previously suggested between respiratory rate and length for planktonic copepods, appears to hold for these two American species, but in the case of Temora the modified formula suggested by Gauld and Raymont (1953) must be used. The relationship applies also to Pseudocalanus minutus. Tortanus discaudatus has been found to have a higher rate as determined experimentally. It is suggested that this high rate is associated with the carnivorous feeding of this copepod. Experiments on the respiration of Eurytemora herdmani show that females have a considerably higher oxygen demand than males, though the difference becomes only slight when due allowance is made for the difference in size between the sexes. Some experiments conducted on the respiratory rates at 15° and 20°C suggest that Eurytemora herdmani, in contrast to the other calanoids investigated, does not show any increase in respiratory rate beyond 15°C. In the laboratory lack of feeding in Tortanus is associated with a marked decline in respiratory rate; to a lesser extent a reduction in respiration with lack of food has been observed in Centropages hamatus.