The Secretion Process of Liquid Silk with Nanopillar Structures from Stenopsyche marmorata (Trichoptera: Stenopsychidae)

Abstract

Stenopsyche marmorata larvae spin underwater adhesive silk for constructing nests and capture nets. The silk can be divided into fiber and adhesive regions, according to their function. The silk fiber region has a two-layer structure: a core layer situated at the center of the fiber and S. marmorata fibroin, the major component of the silk. In the anterior part of the anterior silk gland, the morphological characteristics suggest that the silk insolubilization leading to fibrillation occurs by luminal pH neutralization. The adhesive region is composed of three layers: the outermost (OM), B, and C layers. On the B layer, coated with the OM layer, numerous nano-order pillar structures (nanopillar structures) are located at regular intervals. A nanopillar structure is approximately 40 nm in diameter and 125 nm in length. The precursor materials of the nanopillar structure are electron-dense globules of approximately 25 nm in diameter that are located in the A layer of the lumen of the middle silk gland. The precursor globules autonomously connect to one another on the B layer when the liquid silk is transported to the lumen of the bulbous region. The nanopillar structures probably contribute to the strong underwater adhesion of S. marmorata silk.

Organization of dermal glands and characteristic of secretion in the freshwater mite, Limnesia maculata (O. F. Müller, 1776) (Acariformes, Limnesiidae)

“…This process may depend on the molecular composition and molecular order in the threads themselves. For instance, in insects' silk glands molecular precursors of the silk protein (fibroin and sericin) may be traced during its formation within the secretory granules and further in the gland lumen (see Akai, 1984;Alberti & Storch, 1976;Ashton et al, 2011;Engster, 1976;Hatano & Nagashima, 2015;Kerkam et al, 1991). In water mites, the composition of silken tube-like threads is more likely realized on the supramolecular level where the combination of fibrillary proteins is quite complex.…”

When phylogeny and ecology meet: Modeling the occurrence of Trichoptera with environmental and phylogenetic data

“…The shelter-making behavior of many genera in this Order is another relevant specific interference of pH on Trichoptera populations. Acid water may impair the physical integrity of compounds used by the larvae to build the shelters, portable cases and cocoons, as the reduced pH has a high potential of oxidizing and corroding organic structures (Ashton, Taggart, & Stewart, 2012;Hatano & Nagashima, 2015;Stewart, Ransom, & Hlady, 2011). pH reduction was the main causal factor in an increased mortality of zebra mussel (Dreissena polymorpha), as available calcium is reduced in acidic water (Hincks et al, 1997).…”

Dual-Mode Cross-Linking Enhances Adhesion of Silk Fibroin Hydrogels to Intestinal Tissue

“…In the search for new functional bioadhesives, researchers have turned to nature − for inspiration on materials that show high adhesive strength in wet environments. Among these, mussels stick to organic and inorganic surfaces, and the adhesion has been attributed to mussel foot proteins (mfps). , mfps are rich in 3,4-dihydroxyphenylalanine residues, which contain a pendant 1,2-dihydroxybenzene (catechol) functional group , that exhibits different oxidation states: a reduced (catechol) state that can adhere by coordination and the oxidized (quinone) state that can react with other functional groups (e.g., primary amines and thiols) and cross-link with other quinones. − Catechol functional groups have been incorporated into polymers in different ways, including by polymerizing monomers that contain catechol pendant groups, − by functionalizing synthetic − and natural polymers, ,− and by enzymatically introducing the catechol group on proteins. − A particularly impressive example is the polymers synthesized by copolymerizing styrene and dihydroxystyrene monomers, which have high shear strengths that rival commercial glues but are not soluble in water and therefore are not yet suitable for internal use .…”