Comparison of defecation rates of Limnodrilus hoffmeisteri Claparède (Tubificidae) using two different methods

Abstract

The defecation rate of the tubificid oligochaete, Limnodrilus hoffmeisteri Claparede was measured by using inverted and upright defecation chambers. Worms cultured using the upright method consistently produced larger amounts of feces (45 to 110%) than those in the inverted method (P < 0.01). The average defecation rate for the upright method was 0.69 ± 0.058 (95% CL) mg feces mg' dry weight h-l compared with 0.41 + 0.033 (95% CL) mg feces mgl dry weight h' for worms using the inverted method.Oligochaetes can have significant effects on the physico-chemical status of the uppermost sediments and presumably on the overlying water. The feeding activity of tubificids is well known as an important process in vertically mixing sediments in the Great Lakes (e.g. Davis, 1974;Robbins et al., 1979). These oligochaete worms feed anterior end down with,t.he posterior end extending a few millimeters to several centimeters above the sediment water interface where the defecated material is deposited.During an on-going research program to determine contaminant mobility mediated by biota, a comparison of methods for estimating the defecation rate of Limnodrilus hoffmeisteri Claparede was made to determine the best technique to be used in studying the transfer rates for particlebound organic pollutants. The comparison was made between the method originally described by Alsterberg (1922) and later used by Appleby & Brinkhurst (1970) which relies on inverting vials containing worms for the collection of feces and a method we developed in which the worms remain in their normal orientation. This paper reports the defecation rates of L. hoffmeisteri using both methods. Materials and methodsThe worms were collected from the Milwaukee Harbor, in 6-7 m of water with an Ekman grab. The worms and sediment were placed in buckets with lake water, returned to the laboratory and stored at room temperature (23 C) for about eight months.Worms were hand-picked from 250 m screened samples of Milwaukee Harbor sediment. Approximately 350 L. hoffmeisteri were placed into a cylinder for 12 h containing 250 Mm screened Lake Michigan sediment. This sediment, used in the experiments, was collected by Ponar grab from a depth of 100 m in Lake Michigan at a site located approximately 11 km northeast of Milwaukee Harbor. Mud samples were washed through a 250 Mm screen into buckets to eliminate large organisms. The screened residues were allowed to settle overnight, after which the supernatant was removed and the mud thoroughly homogenized.Following the 12 h adjustment period, the Lake Michigan sediment samples were screened a second time. Immediately thereafter, L. hoffmeisteri were randomly sorted into each of 20 petri dishes containing lake water. An attempt was made to select healthy specimens of approximately the same size Hydrobiologia 111, 181 184 (1984).

Ecology and Biology of Marine Oligochaeta – an Inventory Rather than another Review

“…The exchange of solutes and pollutants at the water/sediment interface is further increased by the continuous reworking of sediment through the digging and feeding activity of most endobenthic fauna. Kaster et al (1984) calculated for Limnodrilus that sediment up to several times its own body weight is brought to the surface every day via defecation. Grossly enhanced diffusion and reworking of sediment by the various littoral oligochaete species will substantially contribute to the overall exchange of solutes, an important factor in sediment biogeochemistry.…”

The role of tubificid worms (Limnodrilus hoffmeisteri) in sediment resuspension: a microcosm study

“…Tubificid worms ingest sediment particles at depth and defecate onto the sediment surface when they have burrowed into the sediment (Davis, 1974b;Kaster et al, 1984). Their defecation rate is surprising; for example, the volume of sediment defecated by tubificids is 17 mL per worm per year at 10 xC (Davis, 1974a), and the defecated mass is 0.69 mg of fecal pellets per mg of dry worms per h (Kaster et al, 1984).…”

“…Their defecation rate is surprising; for example, the volume of sediment defecated by tubificids is 17 mL per worm per year at 10 xC (Davis, 1974a), and the defecated mass is 0.69 mg of fecal pellets per mg of dry worms per h (Kaster et al, 1984). Owing to the worms' high defecation rate, a large quantity of fecal pellets cluster on the sediment surface.…”

“…Tubificids are conveyor-belt feeders that ingest particles in deep sediments and egest them on the sediment surface in the form of pseudofeces (Kaster et al, 1984;Dafoe et al, 2011). The activities of these worms alter sediment stratification (Matisoff et al, 1999;Nogaro et al, 2007;Dafoe et al, 2011), increase sediment water content and porosity (Fukuhara, 1987;Zhang, 2010), change the distribution of the sediment particle size (Ciutat et al, 2006;Zhang, 2010;Dafoe et al, 2011) and alter the oxygen and nutrient dynamics in the sediment and across the sediment-water interface (Matisoff et al, 1985;Mermillod-Blondin et al, 2005;Zhang et al, 2010).…”

Toxicology and Laboratory Studies

“…Faeces were collected using the method of Kaster et al (1984) with defecation chambers and expressed on a dry weight basis normalised by averaged post-experimental measurements of body weight (mg dw g −1 worm day…”