Aerobic and anaerobic metabolism of the freshwater oligochaete Tubifex sp.

Abstract

The freshwater oligochaete lbbifex shows several mechanisms of metabolic adaptations, enabling the worms to occupy saprobial habitats of extremely variable oxygen content. Under normoxic conditions the metabolism of the worms is mainly aerobic with a respiratory ratio of 0.7. Under hypoxic conditions, metabolism of energy sources via aerobic and anaerobic pathways is observed. During complete anoxia acetate and propionate are the main products of glycogen degradation and they are excreted in constant rates into the water. A retransfer of the worms to aerobic conditions enables them to regain aerobic metabolic state within about 60 min.In two Tubifex habitats, which we have characterized, concentrations of dissolved organic material (DOM) were low in the surface water, but high in the interstitial water from sediments. The short-chain fatty acids acetate and propionate reached concentrations up to 1 mmoleAiter. Employing radioisotope techniques, we demonstrated that Tubifex can achieve an integumentary uptake of acetate and propionate from artificial tap water at naturally occurring concentrations of 5 to 1000 p M . Levels of uptake (600 to 800 nmoles/g w.wt.hr) and transport characteristics are very similar to those of marine invertebrates associated with detritus rich sediments. The uptake is susceptible to inhibition by structurally analogous compounds and to metabolic inhibition. Furthermore, DOM uptake in lhbifex is susceptible to inhibition by oxygen depletion, ouabain and Na+ -depletion. The results may suggest that a carrier system for DOM transport exists in the integument of the worms. The uptake system is highly specific for aliphatic C2 and C3 carboxylic acids. The absorbed volatile fatty acids are rapidly metabolized. Only 15 min after absorption, a considerable amount of radioactivity is present in the glycogen storage of the animals. Depending on the substrate concentration assumed to be available for uptake, up to 40 per cent of the oxidative requirement of the worms may be attained by using dissolved organic material from the interstitial water of their habitat.Supported by the Deutsche Forschungsgemeinschaft (Ho 631/9-9).

First phase of macroinvertebrate repopulation of Lake Orta (Buccione Basin) after liming

“…The different bathymetric distribution of the two species of Tubificidae is dependent on a set of factors among which those linked to the chemical-physical characteristics of the sediments and the depth undoubtedly play a major role (Nalepa & Thomas 1976;Barton 1988;Mc Murtry et al 1983). Both species prefer a substrate made up of silt and sand, but while Limnodrilus hoffmeisteri in lakes normally colonises the littoral and sub-littoral layers, Tubifex tubifex has a preference for the deep zone, thanks to its ability to reproduce and increase even at temperatures below 10 °C and to survive for long periods at low oxygen concentrations (Milbrink 1980;Hoffmann et al 1986;Anlauf & Neumann 1997).…”

The Immune Response to the Myxozoan Parasite Myxobolus cerebralis in Salmonids: A Review on Whirling Disease

“…Whirling disease affects multiple salmonid fishes with varying severity and disease onset [10,11]. Clinical signs can be observed in Chinook salmon (Oncorhynchus tshawytscha), brook trout (Salvelinus fontinalis), sock eye salmon (Oncorhynchus nerka), rainbow trout (Oncorhynchus mykiss), and brown trout (Salmo trutta) [10,12,13]. Although different studies have revealed clinical progression in brown trout, rainbow trout is considered the most highly susceptible host [14][15][16].…”