Switching Between Deposit and Suspension Feeding in Coastal Zoobenthos
83
causes a strong current to move posteriorly along the midline of the animal.
The second gnathopods and first two pairs of peraeopods are heavily set with
plumose setae, and suspended material is retained on this filter-screen. Every
few seconds the first gnathopods close towards the midline, scraping food
material off the posterior limbs and passing it forwards to the mouthparts.
The feeding method suggests that detritus and the micro flora associated with
sand grains make up the main food source. Thus, suspension feeding does
occur, but it is combined at times with swirling up of sand grains from the
bottom, almost a form of deposit feeding.
Two feeding modes of the amphipod Corophium volutator have been
described by Medows and Reid (1966). C. volutator feeds on surface sediment
particles or on suspended matter by bringing these food items into its shallow
U-shaped or semicircular tube in the sediment (Fig. 4.1a). In the surface
deposit-feeding mode, C. volutator gather particles from the sediment surface
with its enlarged second antennae. In the suspension-feeding mode, C. volutator extends its body along the tube and feeds by filtering particles from a
pleopodal current with a basket formed by the finely plumose setae of the
second gnathopods. Fenchel et al. (1975) found that C. volutator ingests particles between 4 and 60 flm and this particle size comprises nearly the total
volume of the gut content. It was found highly probable that C. volutator can
directly utilise suspended particles, e.g. small planktonic algae. The setae of
the second gnathopod indicate that the fine bristles form a regular network
which retains particles larger than about 4 flm. Miller (1984) studied suspension and deposit feeding by C. insidiosum, C. salmon is, and C. spinicorne.
Collection of food particles and subsequent manipulation of the particles
seem to be identical for all studied species of the genus Corophium.
4.1.5 Soft Corals
Soft corals are usually assumed to be passive suspension feeders that are
dependent on suspended particles being carried to them by a current.
However, Slattery et al. (1997) have observed that the colonial nephtheid soft
coral Gersemia antarctica can switch to deposit feeding in the soft sediment
communities of McMurdo Sound, Antarctica. Deposit feeding in G. antarctica
involves bending by means of hydrostatic inflation of the entire colony
against the sediment surface. Gut content analyses revealed a mixed diet
including benthic diatoms, foraminiferans, and particulate organic matter.
The deposit-feeding mode in G. antarctica has apparently evolved to supplement the capture of planktonic prey and seems to be of particular importance
in the Antarctic.
83
causes a strong current to move posteriorly along the midline of the animal.
The second gnathopods and first two pairs of peraeopods are heavily set with
plumose setae, and suspended material is retained on this filter-screen. Every
few seconds the first gnathopods close towards the midline, scraping food
material off the posterior limbs and passing it forwards to the mouthparts.
The feeding method suggests that detritus and the micro flora associated with
sand grains make up the main food source. Thus, suspension feeding does
occur, but it is combined at times with swirling up of sand grains from the
bottom, almost a form of deposit feeding.
Two feeding modes of the amphipod Corophium volutator have been
described by Medows and Reid (1966). C. volutator feeds on surface sediment
particles or on suspended matter by bringing these food items into its shallow
U-shaped or semicircular tube in the sediment (Fig. 4.1a). In the surface
deposit-feeding mode, C. volutator gather particles from the sediment surface
with its enlarged second antennae. In the suspension-feeding mode, C. volutator extends its body along the tube and feeds by filtering particles from a
pleopodal current with a basket formed by the finely plumose setae of the
second gnathopods. Fenchel et al. (1975) found that C. volutator ingests particles between 4 and 60 flm and this particle size comprises nearly the total
volume of the gut content. It was found highly probable that C. volutator can
directly utilise suspended particles, e.g. small planktonic algae. The setae of
the second gnathopod indicate that the fine bristles form a regular network
which retains particles larger than about 4 flm. Miller (1984) studied suspension and deposit feeding by C. insidiosum, C. salmon is, and C. spinicorne.
Collection of food particles and subsequent manipulation of the particles
seem to be identical for all studied species of the genus Corophium.
4.1.5 Soft Corals
Soft corals are usually assumed to be passive suspension feeders that are
dependent on suspended particles being carried to them by a current.
However, Slattery et al. (1997) have observed that the colonial nephtheid soft
coral Gersemia antarctica can switch to deposit feeding in the soft sediment
communities of McMurdo Sound, Antarctica. Deposit feeding in G. antarctica
involves bending by means of hydrostatic inflation of the entire colony
against the sediment surface. Gut content analyses revealed a mixed diet
including benthic diatoms, foraminiferans, and particulate organic matter.
The deposit-feeding mode in G. antarctica has apparently evolved to supplement the capture of planktonic prey and seems to be of particular importance
in the Antarctic.