A histochemical study on the snout tentacles and snout skin of bristlenose catfish Ancistrus triradiatus.

Histological sections of the tentacles of Ancistrus triradiatus revealed that they contain many goblet cells with granule-like sections distributed along the edge of the tentacles (mean 302 cells mm(-1)). Various histochemical methods were used to characterize the contents of the goblet cells. The results indicated that the contents were periodic acid-Schiff (PAS) positive, glycogen negative and no sulphated mucins could be found. The contents of the goblet cells were acid mucins and O-acetylated sialomucins which had high energy content. The snout skin of the male also contained goblet cells with higher density (mean 755 cells mm(-1)) than that of the tentacles. Snout skin of female A. triradiatus, on the contrary, did not contain any goblet cells. Instead, many minute spines could be found. Based on the acid mucins and O-acetylated sialomucins secretions of goblet cells which are of high nutritional values, it is hypothesized that snout tentacle secretions are used to provide nutrients to fish larvae when they are under paternal care.