One of my students has told me about another peculiar behaviour, this time in the
convict cichlid. He had a pair of convicts tending their eggs inside a ceramic skull
(one of those aquarium decorations sold in pet shops). The female, instead of fanning
her eggs in the usual way, used to go to the airstone, take air into her mouth, bring it
back to the nest and release it at the bottom so that the air bubble would float upwards
along the egg batch. She did this repeatedly, to the extent that air was gathering at the
top of the skull, threatening to raise the nest and its content all the way to the surface!
Did she carry air bubbles to provide oxygen to her eggs in the face of localised
hypoxic conditions? George Barlow has provided another interpretation, which may
be better: he has observed a similar behaviour in orange chromides, Etroplus
maculatus, and he saw this as an expression of fry-retrieving behavior (see the page:
Are fishes good parents?). The small bubbles are about the same size as fry. The
parent may be fooled into thinking that the air bubbles are fry (even though its eggs
have not hatched yet), and it tries to bring back those incredibly mobile fry back into
the nest. 3