Page 8 - 11-Bio-12 Nutrition

12. Nutrition eLearn.Punjab

Filter feeders: Many aquatic animals filter the water and digest the particles that they extract

from it.

A common mussel possesses two large gills covered with cilia. The movement of cilia causes a
current of water to enter animal via an inhalent siphon (Fig. 12.6). The water, which enters, contains
the food, such as microscopic algae and protozoa. Secretory cells scattered among cilia produce
sticky mucus which entangles food particles. The trapped food particles are then swept towards
the mouth by the ciliary movement. Certain types of whales are also filter feeder.

Fig. 12.6 Filter feeding in mussel

Fluid feeders: When the food is ingested in liquid form the animals are classed as fluid feeders.

Aphids and mosquitoes are the examples. Aphids suck the phloem juices out of the green stems
by inserting their delicate stylets. The female mosquito is also a fluid feeder because it sucks blood
from the skin capillaries by piercing the skin with the help of tubular mouth parts.

Macrophagous feeders: Animals, which take in food in the form of large pieces, are

macrophagous feeders. Tentacular feeding, scraping and seizing prey are the common methods of
macrophagous feeding. Feeding in Hydra is the example of tentacular feeding.

Scraping type of feeding occurs in the garden snail (Helix). It feeds by using rasping organ, the
radula. Leaves are held by the lips of the snail. The radula moves back and forth over the leaves

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