Components of mucus of terrestrial slugs (Gastropoda)

Abstract

Mucous secretion by the body wall of the terrestrial slugs (Ariolimax columbianus, Arionidae; and other species) was found to involve at least three distinct stages--release of vesicles, formation of granules, and organization of strands. Mucus is stored intracellularly in membrane-bound vesicles, and these are shed intact from the mucous cells. Disruption of the vesicle membrane, with release of contents, can be effected by endogenous lytic agent(s), as well as by exogenous surfactants, lipid solvents, or hypotonic media. Thereupon 1-micron granules are released. These may be stable, or they may change to material that is finely granular or in the form of strands; the transition to strands is facilitated by shear stress exerted through the fluid containing the mucous components. Lectins organize, or are organized with, the strands, as evidenced by agglutination of erythrocytes on them. Mucous formation, as seen in the living slug, differs markedly from the one-step process of exocytosis of fluid mucus inferred from studies of mucous membranes fixed for ultrastructural investigation.

The relative contribution of calcium, zinc and oxidation-based cross-links to the stiffness ofArion subfuscusglue

“…This network of fibers would form the primary structure of the glue. Such large fibers have been reported in A. columbianus glue (Deyrup-Olsen et al, 1983). Once the fibers are formed, they may be cross-linked further, with imine bonds forming and electrostatic interactions becoming coordinate covalent bonds as the ligands are brought closer together.…”

“…It is likely that the manner of mixing is essential as well. The mucus of terrestrial slugs is secreted in discrete, membrane-bound packets (Deyrup-Olsen et al, 1983). When they are intact, the secretion is watery, but once they rupture, the glue rapidly sets.…”

“…When they are intact, the secretion is watery, but once they rupture, the glue rapidly sets. Mechanical shear or calcium are sufficient to rupture these packets (Deyrup-Olsen et al, 1983). Furthermore, there appear to be two or three primary types of adhesive cells that secrete different components, with one identified as a calcium cell, one secreting mucopolysaccharides and another that secretes a large volume of fluid and some protein (Luchtel et al, 1984;Smith, 2010).…”

Adhesive defence mucus secretions in the red triangle slug (Triboniophorus graeffei) can incapacitate adult frogs

“…Animals have evolved a diverse array of anti-predator traits, including those that are physical (camouflage, mimicry, and weaponry), behavioural (defensive displays, colouration), and chemical (venom, noxious chemicals). The production of mucus is a prime example of a chemical response to predation risk which has been recorded amongst velvet worms (Baer & Mayer, 2012), echinoderms (Flammang, Demeuldre, Hennebert, & Santos, 2016), fish (Schubert, Munday, Caley, Jones, & Llewellyn, 2003;Shephard, 1994), arthropods (Betz & Kölsch, 2004), lizards (Brau, Lanterbecq, Zghikh, Bels, & Damman, 2016), aquatic gastropods (Rice, 1985), terrestrial slugs (Barber et al, 2015;Deyrup-Olsen, Luchtel, & Martin, 1983), and amphibians (Arnold, 1982;Evans & Brodie, 1994;Graham, Glattauer, Li, Tyler, & Ramshaw, 2013). Such bioadhesives are typically secreted quickly and exhibit a rapid curing process, with some able to be exposed for weeks without losing their bonding capability (von Byern et al, 2017).…”

“…This has been recorded among the terrestrial slugs, which are very susceptible to predation due to their lack of a protective shell, soft bodies and slow pace. This defence-specific mucus is often distinct from the usually thin and slippery mucus produced for the purposes of lubrication and locomotion, acting as a protective barrier that prevents contact between the potential threat and the slug's body (Deyrup-Olsen et al, 1983;Smith, 2006).…”