Irregular helicoids in leech cocoon membranes

Roberto Marotta, Daniel H. Shain

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Helicoids in the cocoon membrane of leeches Theromyzon tessulatum and Erpobdella punctata comprise a twisted superposition of layers, each containing a variable number of planes formed by unidirectional fibrils. Straight fibrils intersecting at different angles were displayed in tangential sections through the cocoon wall of each species. When the sectioning angle was below a certain value (i.e., the critical angle), bow-shaped lines apparent in oblique sections were replaced by a succession of layers containing straight fibrils, permitting a direct measurement of step-angle change between successive layers in a helicoid. By this methodology, we determined that no regularities exist in the succession of step-angles or in layer thicknesses within the cocoon membranes, but that the distribution of step-angles between layers was unique for each cocoon type.

Original languageEnglish (US)
Pages (from-to)336-343
Number of pages8
JournalJournal of Structural Biology
Issue number3
StatePublished - Jun 2007

All Science Journal Classification (ASJC) codes

  • Structural Biology


  • Bow-shaped lines
  • Egg capsule
  • Erpobdella
  • Theromyzon
  • Twisted tissue


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