The freshwater oligochaete Tubifex tubifex is able to absorb 14C‐labeled short‐chain carboxylic acids (VFA) from ambient water (Hipp et al., '86). In this paper evidence is given that VFA are transported across the body surface (autoradiography) and not taken up to any significant extent by bacteria or accumulated on the surface layer. Absorbed carboxylic acids are metabolized, as shown by the appearance of label in respiratory Co2 as well as in glycogen content. Rates of uptake are determined by the metabolic state of the worms. Under anoxic conditions, uptake is rapidly reduced. However, only 30 to 60 minutes of aerobic recovery were needed to regain aerobic control levels of uptake. Comparison of potential rates of VFA accumulation to rates of oxidative metabolism suggest that acetate and propionate might serve as an important nutritional supplement to these benthic freshwater animals.
The freshwater oligochaete Tubifex tubifex can achieve an uptake of short-chain volatile fatty acids (VFA, acetate and propionate) from artificial tap water at naturally occurring interstitial concentrations of 5 to 1000 pM. The uptake results from a combination of saturable and nonsaturable transport, the former displaying Michaelis-Menten-type kinetics. The saturable component is susceptible to inhibition by structurally analogous substances. The kinetics of the inhibition were found to be competitive. VFA uptake rates are strongly depressed by potassium cyanide and iodoacetate. Furthermore, VFA uptake is susceptible to inhibition by ouabain and to Na' depletion. Ql0 values in excess of two are also consistent with the suggestion that a mediated system for VFA absorption exists in the integument of T tubifex.
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