Hirudinea
Introduction
Leeches. About 500 species (63 in North America) of primary freshwater annelids, some species are secondarily marine or terrestrial.
Leeches. About 500 species (63 in North America) of primary freshwater annelids, some species are secondarily marine or terrestrial.
Recognition
The form is usuallly distinctive. Leeches lack parapodia and setae. They have only 34 true segments, but these may be secondarily annulate. Leeches have anterior and posterior suckers.
Life Cycle
Hermaphroditic with mutual copulation resulting in cross-fertilization. Breeding may be seasonal or occur throughout much of the year, and it may occur only once or many times. They use the clitellum to secrete a cocoon around the eggs. The trochophore larva is passed in the cocoon and miniature adults emerge upon hatching. Life cycles may be univoltine, multivoltine, semivoltine or variable.Trophic Roles
Leeches are primarily parasites or predators.Communities
Usually only modestly complex, but most diverse in our warmer, productive shallow, lentic and slow lotic waters. Leeche species separate mostly by substrate and type of food, some are amphibious.
Economic Importance
Leeches can be a nuisance in swimming areas, they sometimes impact fish and wildlife. They are often difficult to control. Some leeches are still used for bloodletting. Many are heavily used by fish and wildlife as food and by man as fish bait or fly patterns. The importance of these soft-bodied worms in diets is often underestimated. Leechs are also a major research organism in experimental studies.
Zoogeography
The families and many of the species are widely distributed. Many species are shared between continents. The cocoon stage and encysted worms may be transported overland, often aided by larger animals. Many areas are not yet well collected.
Collecting
Most leeches must be removed from the substrate by hand. This may include soft sediments, rocks and logs as well as fish, water birds, amphibians, reptiles and sometimes one's self. Swimming leeches may be taken in bottle traps. Many leeches are much more active at night.
Preservation
Leeches should be slowly killed by poisoning their water with ethanol (or many other things) before fixing them in Kahle's fluid or in 10% formalin. When the fixative is added the worms should not respond to touching, but should not be so far gone that secondary annulations are lost or decomposition begins. Leeches can usually be processed in about 5-20 minutes. The specimens are transferred to 70% ethanol after a day, or more for permanent storage.
Taxonomy
Fairy well studied because of the limited size of the group and the wide distribution of many species.
Some changes after Pennak
Haemopis is now split into Mollibdella grandis, Bdellarogatis blumbeus and Percymoorensis for the remaining species.Synopsis Of Neartic Families
- Family Glossiphoniidae- mouth a small pore on the anterior sucker with protrusible proboscis, no jaws, body flattened and much wider than the head, anterior sucker fused to the head, 1-4 pairs of eyes, brood the eggs and young under the body, predators on invertebrates or temporary parasites on fish, amphibians, reptiles and birds, often found free-living, poor swimmers, 10 genera and 30 species.
- Family Piscicolidae- mouth a small pore on the anterior sucker with protrusible proboscis, no jaws, body cylindrical, anterior sucker expanded and distinctly separate from the body, 0-2 pairs of eyes, do not brood the eggs or young, parasitic on marine and freshwater fishes, rarely found free-living, poor swimmers, 4 genera and 10 species.
- Family Hirudinidae- mouth large, 5 pairs of eyes arranged in a regular arch, usually with jaws and teeth, fixed pharynx is shorter than a third of the body length, large sized, 3 genera and 13 species, predacious or bloodsucking parasites on amphibians and mammals, they are good swimmers.
- Family Erpobdellidae- mouth large, 0, 3, or 4 pairs of eyes never in a arch, no jaws or teeth, fixed pharynx is about one-third the body length, moderate sized, 4 genera and 10 species, free-living predators, good swimmers.
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