Secretion of hementin and other antihaemostatic factors in the salivary gland complex of the giant amazon leech Haementeria ghilianii

Abstract

Biological observations were made on the antihaemostatic activity in the saliva of the giant Amazon leech Haementeria ghilianii. Particular emphasis was placed on determining where the fibrino(geno)lytic enzyme hementin is produced and secreted in the salivary gland complex.

Hungry third-fed Amazon leeches produce about 650 units of hementin, with by far the majority of the activity (75%) in the two posterior glands. The two anterior glands contain much less hementin (12%), and a small amount (12%) resides in the proboscis itself, presumably in the salivary gland ductules. In the anterior gland, hementin appears to be produced by only certain cells. The secretion of hementin is confined to the lumen of the proboscis.

Secretions in the proboscis lumen are rich in antihaemostatic activity, as evidenced by fibrinogenolysis (hementin), prolongation of prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin clotting time (TCT) and Atroxin clotting time, and inhibition of collagen-induced platelet aggregation. In contrast, no anti-haemostatic, including hementin, activity was detectable at the tip. Suprisingly, the wound from the bite by the Amazon leech is not associated with prolonged bleeding. This is in marked contrast to the wound by the European medicinal leech Hirudo medicinalis which bleeds for an average of ten hours. The absence of bleeding is compatible with the interpretation, based on the above findings, that during feeding the Amazon leech does not inject antihaemostatic factors into the host, or at least not in the vicinity of the wound.