Surface secretions of the skin of Blennius (Lipophrys) pholis L.

Abstract

Mucus is secreted to the surface of the body and fin webs of Blennius pholis by superficial epithelial cells and by goblet cells. Some goblet cells secrete sulphated acid glycoproteins, others produce a mucus which is neutral or mixed in its reactions. The superficial epithelial cells of these areas secrete sulphated acid glycoproteins, seen by electron microscopy as electron-lucent or moderately lucent vesicles; this secretion is not normally visible external to the skin in transmission electron microscope (TEM) sections. These cells do not react to the bromphenol blue test for proteins. Over part of the surface of the pelvic fins and the distal parts of the rays of the pectoral fins, the skin contains no goblet cells and bears a thick external secretion, or cuticle, containing protein and glycoprotein which is mainly neutral in reaction, although some cells at the edges of the region secrete weakly sulphated or non-sulphated acidic glycoprotein. The protein content of the columnar superficial epithelial cells of these regions correlates with the fibrous nature of the secreted cuticular layer as seen by TEM; the columnar cells are characterized by extensive ribosomal endoplasmic reticulum and vesicles which stain darkly with phosphotungstic acid, less so with uranyl acetate. The distal part of the cell, containing these vesicles, reacts positively to the PAS stain. In some places the borders of the zones with fibrous cuticle are characterized by cuboidal superficial epithelial cells which give a strong positive reaction to alcian blue at pH I .O, indicating the presence of sulphated acid glycoproteins, but also react positively to the bromphenol blue test for proteins.

Glycoconjugates in the branchial mucous cells of <i>Cynoscion guatucupa</i> (Cuvier, 1830) (Pisces: Sciaenidae)

“…PAS positivity is mainly related to the production of glycoproteins, the alcian blue staining coincides with the carboxylation stage, and the conjugation with sulphated groups with the detection of sulphated glycoproteins (Arellano et al, 1999). Moreover, in some freshwater fish (Monopterus cuchia and Pungitius pungitius), the epidermal mucous cell sulphated proteins predominate in the mucus composition, whereas in marine fish (Blennius tentacularis and B. sanguinolentus), GCs with sialic acid prevail (Whitear and Mittal, 1984). Likewise, in the fresh-water fish Odontesthes bonariensis (Díaz et al, 2004b), sulphated GCs predominate in their gills.…”

“…Likewise, in the fresh-water fish Odontesthes bonariensis (Díaz et al, 2004b), sulphated GCs predominate in their gills. It has been postulated that sulphated GCs deter the proliferation of pathogenic micro-organisms in fresh-water fish which are more likely to become infected in this type of environment (Whitear and Mittal, 1984;Mittal et al, 1994).…”

Functions for fish mucus

“…This layer has been referred to as the cuticle (Whitear, 1970(Whitear, , 1977Whitear and Mittal, 1984) and it may reach considerable thicknesses (up to 10 ~tm) although more typically it is less than 1 Ixm thick. Electron micrographs suggest that, where it occurs, the cuticle is secreted by Malpighian cells (also known as pavement, squamous or filament-containing cells) (Hughes and Wright, 1970).…”

Some new observations on the cytopathology of fin erosion disease in winter flounder Pseudopleuronectes americanus

“…as the author was unable to find a thor- (Clark 1981), and appeared to be secretory based on the fine structural nature of their cytoplasm. Thus, these cells may provide secretions that bathe the skin as has been descnbed by Whitear & Mittal (1984) for the blenny Blennius pholis (L.) and for several species of Indian carp (Singh & Mittal 1990). Lymphocytes routinely found in the fin epithelium of winter flounder, but not described in the plaice, may be involved in the generation of antibacterial immunoglobulins found in the skin mucous of other fish species (Peleteiro & Richards 1985, Alexander & Ingram 1992.…”