Jaw anatomy of the blood-sucking leeches, Hirudinea Limnatis nilotica and Hirudo medicinalis, and its relationship to their feeding habits

Abstract

The triple jaws of the leeches Limnatis nilotica and Hirudo medicinalis (both Hirudinidae, Hirudininae) are compared, using the stereomicroscope and scanning electron microscopy (SEM). The jaws of Limnatis are relatively small, rounded and soft, bearing about 30 flat-topped, rough-surfaced teeth, and papillae which presumably secrete saliva. Limnatis sucks blood in stages from internal soft vascular tissue, often in the pharynx, and may stay inside the host for several weeks. Evidence is strong that it is unable to pierce external skin. Hirudo jaws are rigid, have no papillae and bear about 60 sharp teeth, each tooth possessing a secretory aperture on its side, close to the tip. In contrast to Limnatis, Hirudo is an external feeder. It pierces the skin and usually gorges itself with blood in one meal, after which it detaches itself from the host. It gains from six to nine times its weight in a meal, and remains satiated for 3–18 months. The ingested blood of Limnatis, unlike that ingested by Hirudo, is particulate and resembles a liver homogenate. This is probably a result of some scraping by its teeth as the jaws thrust towards a blood vessel. The relationship between jaw anatomy and feeding habits of L. nilotica and H. medicinalis is shown. Clearly, each species has adapted to the particular environment supplying its food (soft internal tissues, external skin).