Preliminary characterisation and extraction of anterior adhesive secretion in monogenean (platyhelminth) parasites

Abstract

Secreted anterior adhesives, used for temporary attachment to epithelial surfaces of fishes (skin and gills) by some monogenean (platyhelminth) parasites have been partially characterised. Adhesive is composed of protein. Amino acid composition has been determined for seven monopisthocotylean monogeneans. Six of these belong to the Monocotylidae and one species, Entobdella soleae (van Beneden et Hesse, 1864) Johnston, 1929, is a member of the Capsalidae. Histochemistry shows that the adhesive does not contain polysaccharides, including acid mucins, or lipids. The adhesive before secretion and in its secreted form contains no dihydroxyphenylalanine (dopa). Secreted adhesive is highly insoluble, but has a soft consistency and is mechanically removable from glass surfaces. Generally there are high levels of glycine and alanine, low levels of tyrosine and methionine, and histidine is often absent. However, amino acid content varies between species, the biggest differences evident when the monocotylid monogeneans were compared with E. soleae. Monogenean adhesive shows similarity in amino acid profile with adhesives from starfish, limpets and barnacles. However, there are some differences in individual amino acids in the temporary adhesive secretions of, on the one hand, the monogeneans and, on the other hand, the starfish and limpets. These differences may reflect the fact that monogeneans, unlike starfish and barnacles, attach to living tissue (tissue adhesion). A method of extracting unsecreted adhesive was investigated for use in further characterisation studies on monogenean glues.