Bristles and Barbs Capture Minute Foods

a calanoid capepod seen on a black background, its body glowing yellow with red spheres at its back and two long appendages with small barbs at its front

Biological Strategy

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Capture, Absorb, or Filter Organisms

Many living systems must secure organisms for food. But just as one living system must capture its prey to survive, its prey must escape to survive. This results in capture and avoidance strategies that include trickery, speed, poisons, constructed traps, and more. For example, a carnivorous plant called the pitcher plant has leaves formed into a tube that collect water. Long, slippery hairs within the tube face downward. When insects enter the tube seeking nectar, they lose their footing and slide inside, unable to climb out and escape being eaten and digested by the plant.

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Capture, Absorb, or Filter Solids

Some living systems must secure solid particles such as sediment, usually to keep the particles from hindering their health or activity. The most common way in which they do this is through filtering. To be effective, a filtering system must be appropriate to the sizes of solid particles to be captured and must capture only what is needed. It must also be effective in the appropriate media–air, water, or sometimes solids like soil. An example is mangroves, which are trees that grow along ocean coasts. Their root system slows down and settles sediment out of the water, building up soil to support the mangrove ecosystem.

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Suspension-feeding appendages of Calanoid copepods capture minute particles and organisms from the surrounding water with the help of attached bristles and barbs.

“Many aquatic animals feed on small particles that they remove from the surrounding water using suspension-feeding appendages…Calanoid copepods are small (of the order of millimeters in length) planktonic crustaceans that can be extremely abundant in oceans and lakes…the spectrum of particles removed from the water by different copepods varies. A feeding copepod propels a current of water past itself by flapping four pairs of appendages; this is the ‘scanning current’. When a parcel of water containing a food particle nears a copepod, the animal actively captures that water and particle using another pair of appendages, the second maxillae…short appendages bearing long bristles, called ‘setae’. The setae are studded with barbs, called ‘setules’. During capture motion, the second maxillae fling apart, thereby sucking water between them, and then squeeze back together again over the water. During the squeeze, the only escape route for the water is between the setae of the second maxillae. Particles retained within the basked formed by the squeezing second maxillae are then combed into the mouth by another pair of appendages.” (Koehl 1983:1, 3, 4)

Last Updated August 20, 2016

References

Journal article

The morphology and performance of suspension-feeding appendages

26/02/1983 | Koehl, M. A. R.

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