Elaborate ultrastructure of the Hirudo (Annelida: Hirudinae) cocoon surface

Abstract

Species of medicinal leeches (Hirudo medicinalis, H. verbana, and H. sulukii) secrete hard-shelled cocoons. When initially deposited, a cocoon is surrounded by a foam. Over a short time, the foam is transformed into a three-dimensional structure. We show here that this peripheral structure likely forms by the solidification and dehydration of a moderately viscous, proteinaceous substance that surrounds bubbles of various sizes. The resulting matrix-like structure comprises a network of curved branches juxtaposed at ∼120° and taper in width as a function of distance from the outer cocoon wall. The material is proteinaceous, and traps environmental material in its composition, especially silicon. The geometry of compartments and abundance of silicon on branch surfaces suggest a mechanism for trapping water to prevent desiccation in a terrestrial environment.

Studying cuticle shedding in three species of leeches (Hirudinea, Annelida)

“…and Haemopis cf. sanguisuga individuals are forced to leave the water to lay their cocoons (Ceylan et al, 2017; Petrauskiene et al, 2011; Saidel et al, 2018), whereas individuals of Erpobdella cf. octoculata lay their cocoons under water (Murphy & Learner, 1982; Sawyer, 1970).…”

Vol:37 Issue:3

“…Natural behaviour of medicinal leeches to deposit their cocoons dark, damp places into moist soil on terrestrial habitat (Kutschera and Roth, 2006;Kutschera and Shain, 2019). Cocoons initially surronded by a foamy substance then take the final solid form (Saidel et al, 2018) like an egg covered by thin sponge. Saidel et al (2018) thought this three-dimensional structure of cocoon protects itself from desiccation and displacement.…”

“…Cocoons initially surronded by a foamy substance then take the final solid form (Saidel et al, 2018) like an egg covered by thin sponge. Saidel et al (2018) thought this three-dimensional structure of cocoon protects itself from desiccation and displacement. Also leeches may have a instict to protect their cocoons by deposting them into moist soil.…”

Hirudinea Lamarck 1818: Evolutionary origin and taxonomy of the six medicinal leeches (genus Hirudo) known today

“…Both species reproduce by reciprocal insemination via copulation of two fertile hermaphrodites, and deposit their cocoons into moist soil (Figure 2). From these egg sacs, which are characterized by a complex fine structure that protects the cocoons from desiccation [16], juvenile leeches hatch that show the species-specific colour pattern of their parents.…”