Fungal Attack on Frog Eggs

Dr. Clive Cummins
Last update: 17 August, 2002

Whilst trawling through the literature the other day I came across a paper entitled Two fungi lethal to frogs in Central America by Jaime Villa (Copeia 1979 (4): 650-655).  During the course of his research the author had found 18 species or growth forms of fungi associated with frog eggs in Nicaragua and Costa Rica.  While most grew on dead eggs (sometimes spreading to smother developing embryos in the same clutch) two were clearly different.  The two species or growth forms concerned 'attacked and killed' healthy, developing embryos and appeared to be restricted to frog clutches.  Neither produced reproductive structures that could be used to identify them, nor was it evident how they infect new clutches of eggs.  However, larvae of a phorid fly often fed upon one type of fungus.

This was identified as Megaselia scalaris, and the author suggested that fragments of the fungus might be carried around by the fly. Most of the work was carried out on clutches of eggs of tree frogs namely Agalychnis, Phyllomedusa and Centrolenella.  The author noted that healthy embryos of many frog species were resistant to attack by a variety of fungi, and suggested that the parent frogs might have introduced secretions with fungicidal properties.  Apparently, egg clutches of centrolenid frogs, which 'guard' their eggs, were less often infected by fungi than clutches of phyllomedusine frogs, which do not sit on their eggs.  Another possible means by which parent frogs might reduce fungal attack on their eggs is by physically disturbing the eggs thereby breaking the fungal threads, or hyphae.

Quite a few keepers of Dendrobatid frogs remove eggs as they are laid, for 'safe keeping'.  This may be necessary if eggs would otherwise be eaten, but it does mean that the parents are unable to do whatever they would normally do to look after their offspring.  This might take the form of 'watering', applying skin secretions, pushing the eggs about or any combination of these. If you take eggs away from your frogs, and if you have problems with fungal growth on healthy embryos, you might try simulating the movements of a parent frog. This could, perhaps, be achieved by gently pushing the egg capsules with a small, wet paintbrush (the type used for artwork - not painting walls) say, twice a day.  If you get clutches regularly, do an experiment - give some clutches this treatment, but not others. Above all, whether this works or not, let us know what happens.