Parasitic adaptations of the leech
A leech is built for blood: suckers cling, jaws cut, hirudin stops clotting, the pharynx pumps, and the crop stores blood for months.
Adaptations and how they help
| Adaptation | How it helps |
|---|---|
| Anterior and posterior suckers | Hold the leech firmly to the host while it feeds |
| Three jaws with fine teeth | Cut a painless, Y-shaped wound in the host's skin |
| Salivary glands that secrete hirudin | Hirudin is an anticoagulant: it stops the host's blood from clotting, so blood keeps flowing |
| Muscular pharynx | Works like a pump to suck blood |
| Large crop with chambers and caeca | Stores blood, enough for several months, so the leech needs to feed only rarely |
| Little need for digestive juices | Stored blood is digested slowly, so elaborate digestive glands are not needed |
| No parapodia or setae | A smooth body with suckers suits clinging to a host; bristles are not needed |
Why it is a successful parasite
An ectoparasite must find a host, hold on, feed quickly and then survive until its next meal. The leech manages all four. Its eyes and skin receptors sense movement in the water. Its suckers hold on. Its jaws, hirudin and pumping pharynx let it take a big meal in a short time. Its crop lets it live for months before it needs another host.
Leech vs earthworm (both annelids)
Comparing the two shows why the leech has no setae: it clings with suckers instead.
When a leech drops off after feeding, the small wound may keep bleeding for a while: that is hirudin at work. Washing the bite with soap and clean water and pressing it with a clean cloth helps it stop.
1 marks: “Name the anticoagulant present in the saliva of a leech.” Hirudin.
2 marks: “What is hirudin? What is its role?” An anticoagulant secreted by the salivary glands of the leech; it stops the host's blood from clotting while the leech feeds.
4 marks: “Write the parasitic adaptations of the leech.” Suckers for attachment; jaws cut a painless Y-shaped wound; hirudin stops clotting; pharynx sucks blood; crop stores blood for months; no parapodia or setae; less need for digestive juices.
'Super Jumbo Hungry Parasites Cling': Suckers, Jaws, Hirudin, Pharynx, Crop (and no setae).