The biological function of hementin in the proboscis of the leech Haementeria ghilianii
Physiology published in Blood Coagul Fibrinolysis (1991)
Abstract
The giant Amazon leech Haementeria ghilianii feeds by inserting an exceedingly long tubular proboscis (up to 10 cm) deep into its mammalian host. The wound from its bite is not associated with prolonged bleeding because all antihaemostatic factors, including the fibrinogenolytic enzyme hementin, appear to be secreted exclusively into the lumen of the proboscis. It is in this narrow lumen that blood first comes into contact with hementin, the secretion of which is under neuronal control from the brain. During feeding, about 15 ml of blood are sucked through the proboscis at the rate of approximately 0.14 ml/min. A complete passage of blood takes less than 1 min, much faster than the approximately 6 min needed for coagulation (fibrin formation). Therefore, it is unlikely that hementin functions in the proboscis simply to prevent fibrin formation. Of greater risk is platelet aggregation which can occur within 1-2 min. The formation of a platelet-rich clot within the proboscis could make the proboscis non-functional. Hementin's unique ability to dissolve platelet-rich clots offers a way of restoring blood flow through the proboscis. Hementin is able to disaggregate platelets by breaking the fibrinogen crosslink between platelets. Hementin's unique cleavage site in the connector region of platelet-bound fibrinogen is thought to be a most effective mechanism for eliminating the crosslinking.
Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.
Summary
Hementin in the giant Amazon leech's tubular proboscis functions primarily to disaggregate platelet clots — not to prevent fibrin formation per se — preserving proboscis patency during the ~1-minute blood passage.
Why This Matters for Hirudotherapy
This study investigates the biological function of hementin in the proboscis of Haementeria ghilianii during feeding, finding that the enzyme is secreted under neuronal control exclusively into the proboscis lumen where blood first contacts it. The abstract reports that blood transits the proboscis in under one minute—faster than the approximately six minutes needed for fibrin formation—suggesting hementin's primary role is not preventing coagulation but rather dissolving platelet-rich clots by cleaving fibrinogen crosslinks between platelets to maintain proboscis patency during feeding. This is relevant to ASH's domain as it illuminates the functional ecology of a leech anticoagulant in its natural feeding context. However, the study concerns a non-Hirudo species' feeding physiology rather than clinical hirudotherapy, limiting its direct practical relevance to comparative leech biology.
Citation
The biological function of hementin in the proboscis of the leech Haementeria ghilianii.
Sawyer RT, Jones CP, Munro R · Blood coagulation & fibrinolysis : an international journal in haemostasis and thrombosis, 1991
Added to ASH library: May 26, 2026 · Site last updated: June 18, 2026