What do they look like?
Leeches are segmented worms with suction cups at each end. Their bodies are flattened, much wider than they are thick. They are usually dark colored, often brown or sometimes black or dark green. Some species have no markings, others have spots and stripes. The smallest leeches grow no more than 5 mm, but some big species may get to be more than 25 cm long. Many leech species have one or more pairs of eyes visible on the top of their front end. Leech species that suck blood have sharp teeth. Predatory species may have teeth, or may have only crushing jaws.
How do they grow?
Leeches lay eggs in cocoons, and the babies that hatch out look and behave like little adults. They don't change much as they grow, they just get bigger. Leeches that live in habitats that freeze or dry out during part of the year bury themselves in mud and stay dormant until the habitat improves. Leech growth rate is strongly affected by temperature and food supply. Most species can mature in a few weeks or months if conditions are good.
How do they reproduce?
In most species, each leech has both male and female sex organs, and can both lay eggs and give sperm to another worm. After mating, each worm produces several cocoons containing eggs. The cocoons are protected with a tough layer of protein, and contain one or a few eggs (depending on the species). Most species attach their cocoon to vegetation or debris underwater, but a few put them in damp soil. Leeches reproduce and grow at very different rates, depending on which species they are, the amount of food they get, and the temperature of the habitat they live in. Most grow faster in warmer temperatures.
Key reproductive features:seasonal breeding; year-round breeding; oviparous.
Some freshwater leeches bury their cocoons and then guard them and keep a stream of water flowing over them so the eggs can get more oxygen. Some species attach their cocoons to their bodies, and carry the eggs with them for protection. A few carry their hatchlings with them too, until the little leeches have their first meal.
Parental investment:no parental involvement; male parental care; female parental care.
How long do they live?
Some leeches complete their life cycle in a few months, but many can live for several years.
How do they behave?
All leeches can crawl, and some are good swimmers. They search for prey by following the scent or touch of the animals they want to eat. When they first detect food, they extend their bodies and hold very still, probably to carefully sense their prey.
Tuesday, May 6, 2008
What do they look like?
at 5:27 AM