Filter feeding in the burrowing amphipod Corophium volutator

Abstract

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.

Particle capture mechanisms in suspension-feeding invertebrates

“…The filter is made up of fine bristles (setules) on the setae, and the distance between the bristles is ∼7 µm. The filter basket may efficiently retain particles with diameters > 7 µm, which has been supported by the experimentally measured particle retention efficiency (Møller & Riisgård 2006). Riisgård (2007a) studied the integrated function of the setal filter-basket and the pleopodal pump in C. volutator.…”

Regulation of nitrous oxide emission associated with benthic invertebrates

“…, 2008). Temperature, which can regulate the feeding rate of aquatic invertebrates (Hymel & Plante, 2000; Moller & Riisgard, 2006), may also regulate the metabolic rate of denitrifying bacteria in the gut directly. In other words, seasonal changes in temperature may influence the degree of gut filling (and hence bacterial biomass) and the rate of bacterial N 2 O production in the gut, respectively.…”

“…In aquatic sediments, seasonal variability in temperature and NO À 3 availability regulates denitrification rate and the N 2 O ⁄ N 2 production ratio (Pina-Ochoa & Alvarez-Cobelas, 2006;Silvennoinen et al, 2008). Temperature, which can regulate the feeding rate of aquatic invertebrates (Hymel & Plante, 2000;Moller & Riisgard, 2006), may also regulate the metabolic rate of denitrifying bacteria in the gut directly. In other words, seasonal changes in temperature may influence the degree of gut filling (and hence bacterial biomass) and the rate of bacterial N 2 O production in the gut, respectively.…”

Group sweeping: Feeding activity and filtration rate in the tubiculous amphipod Haploops nirae (Kaim-Malka, 1976)

“…microalgae) was provided using peristaltic pumps with a pure culture of the diatom Thalassiosira weissflogii. The cell concentration was determined using a Malassez cell counting chamber and the relationship between Chl a (µg.L -1 ) and cell concentration (C c 10 3 cell.mL -1 ) was Chl a = 2.7 x Cc (Møller and Riisgård, 2006). To mimic an increasing range of particulate inorganic matter (hereafter PIM), silt (Kaolinite BS1, AGS Montguyon, France) was added to the diet.…”

“…20 µm) corresponding to the particles efficiently retained by Haploops antennae. For the amphipod Corophium volutator, Møller and Riisgård (2006) showed that the distance between two brittles on the gnathopods (filter organs) corresponds to the particle diameter retained with 100% efficiency (i.e. 6-7 µm).…”