A new role for the fleshy tentacles (bristles) on the snout of the male bristlenose catfish (Ancistrus) in feeding the fry under paternal care has been proposed by Taiwanese ichthyologist Hong Young Yan in a study published in the most recent issue of the Journal of Fish Biology.
Yan examined the histochemical properties of the tentacles of male Ancistrus triradiatus by studying tissue sections of the tentacles subjected to various histochemical stains under the microscope.
He found that the edge of the tentacles had numerous goblet (mucus-producing) cells, and that females lacked these cells on the skin of their snouts.
The contents of the goblet cells were acid mucins and O-acetylated sialomucins (mucins are a group of glycosylated proteins, i.e. protein molecules with sugar molecules attached to them) that had high energy content.
Based on this observation, Yan proposed that the secretions produced by the snout tentacles may have a role in providing nutrition to the fry (in a similar manner to the mucus in breeding discus).
However, he stressed that his hypothesis requires further testing, and also proposed other possible roles for the snout-tentacle secretions.
The first alternative hypothesis is that the secretion may have an antimicrobial function that helps to protect the eggs against pathogens.
Another possible function proposed for this secretion is that it is a chemical signal for mate attraction, or male territoriality signalling, or possibly species recognition.
For more information, see the paper: Yan, HY (2009) A histochemical study on the snout tentacles and snout skin of bristlenose catfish Ancistrus triradiatus. Journal of Fish Biology 75, pp. 845"861.