Annelids are heterotrophic. They are metamerically segmented invertebrates. They have a well developed complete digestive system. They feed on soil, small invertebrates or dead and decaying organic matter. According to their diverse habitat, their feeding mechanism differs.
- Earthworms live in the soil. They are soil-eaters. They extract the nutrients from the dead organic matter mixed in the soil.
- Polychaetes are marine. They may be predator, scavenger or filter-feeders. Most of them contain a pair of jaws and eversible pharynx to grab the food in their mouth quickly. Jaws are used to biting food and grasping prey. Filter feeders contain a ciliated crown of palps to filter food going into the mouth.
- Leeches are parasites or predators. The predatory species feed on small invertebrates. They mostly contain eversible proboscis. They swallow their prey. The parasitic species feed on the blood of the host. They suck the blood from the host using their anterior suckers. They secrete a peptide called hirudin to prevent the blood clotting.
Feeding in Earthworms
Earthworms feed on soil with dead and decaying organic matter. Their body is segmented and the unsegmented alimentary canal runs throughout their body from mouth to anus. This type of digestive system is known as ‘tube within a tube’.
The alimentary canal of earthworm consists of a mouth on the 1st segment, i.e. peristomium, which opens into the buccal cavity. The mouth is covered by prostomium and food is ingested through it. The chemoreceptors present there help in identifying the food they eat. It is followed by the pharynx, oesophagus, muscular gizzard, intestine and anus. The function of the gizzard is to grind the soil particles and decaying organic matter. The digestion completes in the intestine followed by absorption of nutrients. The typhlosole region of the intestine increases the surface area of absorption. The undigested food is excreted out through the anus and known as worm castings.
Explore more: Earthworm Digestive System
This was in brief about the feeding mechanism in Annelids. Get access to all the NEET Questions with explanations, only at BYJU’S.