The Respiratory Metabolism of Helminths

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Abstract
The respiratory metabolism of the trema-tode Paramphistomum cervi and the nematodes Haemonchus contortus, Ostertagia circumcincta, Syphacia sp., Heterakis spumosa, Strongylus equinus, and S. vulgaris was examined. The nematodes gave QO2 values ranging from -7.4 to -1.1. When calculated on the basis of the relative surface areas of the parasites the differences in O2 uptake were much smaller. Cyanide inhibited the uptake of O2; R.Q. values ranged from 0.8 to 3.3. Nematodes inhabiting those parts of the gut in which bacterial fermentation is most active generally showed higher R.Q. values. Paramphistomum cervi gave the low QO2 of -0.03, and an R. Q. of 8 or over. Cyanide caused a pronounced increase in the uptake of O2. When the trematodes were incubated aerobically in vitro the R. Q. gradually fell and the activating effect of cyanide decreased. The cyanide activation of O2 uptake of brei prepared from Paramphistomum cervi was not obtained when methylene blue was present. The present investigation has shown that the pattern of respiratory metabolism in helminths may vary, even among morphologically related forms. However, different spp. of parasites from regions of similar physiological activity in the host show some similarity in the nature of their respiratory activity.