An analysis of water flow in tube-living animals

105

Most accounts on suspension feeding assume that mechanical, sievelike filters retain particles from the ambient water Fluid mechanical aspects have been neglected. Suspension feeding is characterized by very low Reynolds numbers. This implies that water processing and particle retention are exclusively determined by viscous forces. Modern filtration theory can therefore be applied to hypotheses on suspension feeding involving mechanical filters. The resistance to water flow through such filters was found to correspond to pressure drops across the filters of about 0.1 to 0.4 mm H,O in flagellates, ciliates, sponges, and ascidians; and of > l mm H,O in copepods and bivalves. These theoretical pressure drops are consistent with the function as filters of ciliate membranelles, pseudopodial collars in flagellates and sponges, and ascidian mucus filters. Ciliary and flagellar water transport operate at very low pressures The pressure drops calculated for copepod second maxillae and bivalve laterofrontal cirri seem to be incompatible with the roles as filters traditionally ascribed to these structures. Recent studies indicate that sievelike models have to b e abandoned in explaining particle retention in copepods and bivalves. Particles seem to be captured by means of mechanisms that do not imply physical interception of the suspended particles Copepods seem to have adopted mechanisms, based on viscous forces, that direct food particles in the surrounding water toward the second maxillae, which eventually capture the parcel of water that contains the particle. In the bivalve gill capture of suspended particles implies transfer from the currents passing through the gill via the interfilamentary spaces to the frontal surface currents along the filaments. Complex patterns of flow arise where the 2 systems of currents meet at the entrance to the interfilamentary spaces. The patterns are characterized by steep velocity gradients which may act on suspended particles and cause them to enter the surface currents, i.e. to b e captured. It remains to be ascertained to what extent fluid mechanics operate in the capture of particles in other metazoan ciliary feeders

Section: Copepodsmentioning

confidence: 98%

Section: Copepodsmentioning

confidence: 99%

Fluid mechanical aspects of suspension feeding

Jørgensen¹

1983

105

“…Peristaltic movements of Arenicola marina cause a waterflow of 40 to 400 m1 h-' through its L-shaped tube, supplying the polychaete with oxygen (Kriiger 1964, Jacobsen 1967, Foster-Smith 1978, Baumfalk 1979. The burrow wallof the tail shaft, consisting of sand grains and detritus tightly cemented with mucus, is about 1 mm thick and relatively impermeable to porewater.…”

Section: Processes In the Tail Shaft Zonementioning

confidence: 99%

Influence of the lugworm Arenicola marina on porewater nutrient profiles of sand flat sediments

Hüttel¹

1990

Bioturbation by the lugworm Arenicola marina L. caused specific changes in porewater nutrient profiles of sandflat sediments. In 2 in situ container expenments, A, manna increased nitrate and decreased ammonia concentrations at the depth ot its burrows. This indicates that A . marina stimulates nitrification in this sediment layer through oxygen supply via its ventilation current. The enlarged zone of nitrification promotes denitrification and thereby, nitrogen release from sediments. Silicate concentrations in the porewater were also affected by A. marina bioturbation. Silicate was flushed out of the sediment with the ventilation current. These findings emphasize the important role of A. marina for nutrient release from Wadden Sea sediments

“…The tube-dwelling amphipod Corophium volutator (Pallas), which lives in shallow soft sediments of coastal waters around Europe, NE America (Lincoln 1979, Murdoch et al 1986) and Japan (Omori et al 1982), feeds on surface sediment or on suspended particles by drawing these food items into its U-shaped tube in the sediment (Hart 1930, Meadows & Reid 1966, Fenchel et al 1975, Foster-Smith 1978, Nielsen & Kofoed 1982, Miller 1984, Hawkins 1985, Gerdol & Hughes 1994a,b, Riisgård & Kamermans 2001. In the surface deposit-feeding mode, C. volutator gathers particles from the sediment surface with its enlarged second antennae.…”

Section: Introductionmentioning

confidence: 99%

Filter feeding in the burrowing amphipod Corophium volutator

Møller¹,

Riisgård²

2006

The present study shows that when suspended phytoplankton cells are present at sufficiently high concentrations the tube-dwelling marine amphipod Corophium volutator (Pallas) filter feeds, but when the phytoplankton biomass reaches a certain low level, both laboratory and field video observations support the hypothesis that C. volutator can switch to surface deposit feeding. Feeding behaviour and quantification of water processing were studied in individuals transferred to glass tubes. Simultaneous clearance of algal cells of different size showed that the setae filter on the second gnathopods retains particles ≥7 µm. The pumping rate (P, ml h -1 ) was measured by video particle tracking, and the relationship between P and body dry weight (W, mg) was found to be P = 53.3W 0.76 . The relationship between P and body length (L, mm) was P = 0.24L 3 + 7.8, and the relationship between temperature (T, °C) and P was P = 5.55T + 3.3. The respiration rate of a 6.5 mm length individual was 0.7 µl O 2 h -1 (15°C), and by relating respiration to P of an individual of this size, it was estimated that C. volutator pumps 108 l water ml -1 O 2 consumed, thus fulfilling the conditions for classification as a true filter feeder. Monthly samples were collected for 1 yr from the shallow (0.8 m) inner part of Odense Fjord (Denmark) in order to follow size and density distribution of C. volutator. By combining filtration rate data with size-and temperature-dependent P data, the area-specific population filtration rate varied between 0.9 in January and 19.4 m 3 m -2 d -1 in June. The half-life of phytoplankton (assuming 100% particle retention efficiency and efficient vertical mixing of the water column) ranged from 14.5 h in January to 0.7 h in June and July. This suggests that the grazing impact of C. volutator may be significantly important in the inner Odense Fjord and other shallow water areas with dense populations of C. volutator.