Mechanics of cocoon secretion in a segmented worm (Annelida: Hirudinidae)
Ultrastructure published in Micron (2016)
Abstract
Clitellate annelids (e.g., segmented earthworms, leeches) secrete proteinaceous cocoons into which eggs are deposited. The process of cocoon production is characterized by the coordinated release of micro-granules from secretory cells positioned asymmetrically within the clitellum. Collectively, these assemble into a tubular cocoon sheath that is sealed at either end by globular opercula. By transmission electron microscopy (TEM), we show here that granules destined to the cocoon operculum in the leech, Erpodbdella obscura, display a series of concentric rings surrounding a structureless core with dimensions approximating a single nanoglobule found in the operculum. Upon their channeling to the surface through narrow tubules, granules are secreted into the cocoon lumen where they appear to fragment upon contact with the operculum matrix. The distribution of partial concentric ring structures throughout the operculum suggests that granular fusion causes dynamic fragmentation of outer surface material, which thereafter integrates into operculum nanoglobules and cavities. Other granules within the same secretory cell display a punctate pattern and likely fuse with the cocoon sheath prior to crystallization.
Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.
Summary
Transmission electron microscopy of Erpobdella obscura cocoon production reveals concentric-ring secretory granules that fuse and fragment during operculum formation. Provides bioadhesion-relevant insight from a leech model.
Why This Matters for Hirudotherapy
The study used transmission electron microscopy to examine how cocoon secretory granules form the operculum in the leech Erpodbdella obscura. It describes coordinated microgranule release from asymmetrically positioned clitellar secretory cells, granules with concentric rings around a structureless core, transport through narrow tubules, fragmentation into the operculum matrix, and fusion into operculum nanoglobules and cavities. For ASH, this is relevant only as basic leech biology, because it concerns reproductive cocoon biomaterials rather than salivary anticoagulants, the therapeutic leech secretome, or hirudotherapy. The abstract reports microscopy findings in a single leech species and provides no human, clinical, or therapeutic data.
Citation
Mechanics of cocoon secretion in a segmented worm (Annelida: Hirudinidae).
Rossi AM et al. · Micron (Oxford, England : 1993), 2016
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