|Foods & feeding|
The general features of a corophiid amphipod (SubOrder Gammaridae) are shown in the accompanying drawing. This may help with the interpretation of feeding methods in the Research Study below.
In burrow-inhabiting corophiids, the main morphological
|Studies on corophiids are considered here, while ones on TALITRIDS and CAPRELLIDS are dealt with elsewhere.|
Research study 1
Burrow-inhabiting Corophium species feed on organic particles that they stir up from the sediment surface or filter-feed from the plankton. A study on food-capture mechanics in 3 species at Friday Harbor Laboratories, Washington using small sections of glass tubing or "sandwich aquaria" reveals that oscillatory motions of mouthparts are employed to ingest selected particles. Experiments on particle size-selection, done in a recirculating flume device, show that particles of a range 5-53µm are sorted and eaten, while 60µm particles are too large. Particles of 9µm diameter are ingested at a rate of >20 . sec-1.
An individual within its tube feeds either by suspension-mode or deposit-mode, often somersaulting and rotating about to change position. Suspension feeding is done as follows: currents generated by beating of the pleopods carry suspended particles into a sieve formed by the double row of plumose setae of the 2nd gnathopods (see Left blue drawing above). From time to time the 1st gnathopods brush these particles into the maxillipeds and maxillae around the mouth. Experiments with dye show that almost all of the pleopodal-generated water stream passes through these sieves. Scissor-like movements of the maxillipeds and maxillae sort the particles, some being moved into the mouth and others being moved anteriorly in a rejection stream.
In deposit-feeding, the amphipod emerges from its tube and uses its 2nd antennae in a scraping motion to collect and form particles into a bolus from the substratum surface (see drawing far Left). The 2nd antennae are greatly extended through large pedunclular expansion. The amphipod then backs into its tube with the food bolus held in its 2nd antennae and sorts the contained particles in the same manner as described for suspension feeding (see Right part of drawing above). The author notes that particle selectivity differs for the 3 species, but is uncertain of the reasons for it. Drawing upper Left courtesy Meadows & Read 1966 J Zool 150: 387.
NOTE the species are spinicorne, insidiosum, and salmonis. They inhabit shallow U- or semicircular-shaped tubes in the sediment
NOTE the particles are spherical polystyrene beads of different diameters. After a feeding experiment, test animals are dissected, and the beads counted and measured from the gut contents
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