9/21/2023 0 Comments Snail leech![]() ![]() They cannot hear, but are sometimes very sensitive to vibrations. Leeches have very poor vision (often they can only tell the strength of light), but are very sensitive to touch. When they first detect food, they extend their bodies and hold very still, probably to carefully sense their prey. They search for prey by following the scent or touch of the animals they want to eat. How do they behave?Īll leeches can crawl, and some are good swimmers. Some leeches complete their life cycle in a few months, but many can live for several years. Most species can mature in a few weeks or months if conditions are good. Leech growth rate is strongly affected by temperature and food supply. 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. They don't change much as they grow, they just get bigger. Leeches lay eggs in cocoons, and the babies that hatch out look and behave like little adults. These animals are found in the following types of habitat.Most leech species are found in shallow, slow-moving freshwater, but some live in the oceans, and a few live in moist soil on land. In Michigan there are at least 40 species, and probably more. Leeches are found all over the world, and there are hundreds of species. Predatory species may have teeth, or may have only crushing jaws. Leech species that suck blood have sharp teeth. Many leech species have one or more pairs of eyes visible on the top of their front end. The smallest leeches grow no more than 5 mm, but some big species may get to be more than 25 cm long. Some species have no markings, others have spots and stripes. They are usually dark colored, often brown or sometimes black or dark green. Their bodies are flattened, much wider than they are thick. But in the lab, they are also fed dead insect larvae, and Civitello worries that in the wild the leeches will prove to have dangerously diverse diets.Leeches are segmented worms with suction cups at each end. The leeches do happily eat many species of snails. “These predators are often not specialists on the snails we want them to eat.” This is a problem that has plagued snail biocontrol, he explains. austinensis does love snails - but it will eat other things too. “If you are indiscriminately killing snails, but you’re not eradicating snails, you’re setting up the possibility that you are weakening competition for food.” And if the leeches leave low populations of big, well-fed snails at large, their infectiousness could mean that snail-borne disease ends up getting worse, not better, he says. ![]() “Having a hard time finding your prey item is indicative of a poor ability to drive it extinct,” he says. Once populations of snails decreased, he notes, the leeches had a hard time finding snails. But he thinks much more research is needed. It’s an interesting idea, says David Civitello, an ecologist at Emory University in Atlanta who was not involved in the study. The leech’s taste for snails suggests that it could be used to control snail populations - and, hopefully, snail-borne diseases. In this video, the leeches seek out and swarm a hapless snail. Helobdella austinensis can’t resist escargot. Using different ratios of leeches and snails, Shain and colleagues put together predator-prey computer simulations that suggested leeches could tank populations of snails within six months. If enough snails were present, one leech could consume 0.97 milligrams of snail per day - roughly the leech’s own weight. austinensis proved an indiscriminate devotee of escargot. The team tested the leeches in the lab with seven different freshwater snail species, and only H. modesta, which can be found in local lakes in New Jersey by turning over rocks. austinensis, a laboratory leech, and two other species, the lab leech H. “And snails are a big problem globally, in terms of health, and so we just connected a few dots.” The leeches aren’t very picky in terms of the types of snails they eat. “Everybody who works in the very small leech world globally, we all know that these particular types of leeches love snails,” says Daniel Shain, an evolutionary biologist at Rutgers University in Camden, N.J. Leeches may be staple frights for horror movie characters, but the animals that should really live in terror of H. ![]()
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