Medicinal Leech Biology
Taxonomy, anatomy, salivary pharmacology, and clinical relevance
Biology vs. clinical evidence: Out of 440+ catalogued salivary proteins, only a fraction has clinical evidence. See the Coverage Map for what is and isn't studied per organ system, the Research Roadmap for ASH's evidence-gap priorities, and Transparency & Trust for the editorial integrity record.
Last updated: March 18, 2026
The medicinal leech is both an FDA-cleared medical device and a sophisticated biological research platform. With 440+ proteins identified in saliva and three clinically relevant Hirudo species, understanding leech biology is essential for evidence-based hirudotherapy practice.
Educational Purpose
Core Topics
Salivary Pharmacology
The Salivary Gland Complex
Overview of 440+ identified proteins across functional groups — anticoagulants, anti-inflammatories, antimicrobials.
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Hirudin — Primary Anticoagulant
The most potent natural thrombin inhibitor — a 65-amino-acid peptide that inspired three FDA-approved drugs.
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Anticoagulation & Antiplatelet
Beyond hirudin: calin, apyrase, saratin — multiple anticoagulation strategies working synergistically.
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Anti-inflammatory Compounds
Hyaluronidase, eglin c, bdellins — the anti-inflammatory arsenal that modulates tissue response.
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Destabilase — Dual Function
Unique enzyme with both fibrinolytic AND antimicrobial activities — research potential for thrombolysis.
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Antimicrobial Peptides (AMPs)
Hirunipins, theromacin, and other defense molecules — novel candidates against drug-resistant bacteria.
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Taxonomy & Species
Classification & Taxonomy
Phylum Annelida to genus Hirudo — why accurate identification matters for FDA compliance.
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Species Guide
H. medicinalis, H. verbana, H. orientalis — comparative profiles.
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Species Identification
Morphological and molecular methods for identifying medicinal leech species.
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Anatomy & Physiology
Medicinal Leech Anatomy
32 segments, tripartite jaw, dual suckers, and the remarkable crop-based blood storage system.
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Nervous System & Sensory Biology
21 ganglia, ~10,000 neurons — how the medicinal leech finds its host.
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Feeding Mechanism & Blood Processing
The complete feeding cycle — from attachment to passive bleeding.
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