paradoxical frogs

Well, I’ve just got back from a series of conferences (3 in the space of 10 days) – & all of them about teaching! I was getting pretty tired by the end of it all, but at the same time it was really good to be able to spend time talking about teaching (& about research into teaching & learning) and to pick up some tips from some of the country’s top tertiary teachers.

One of those teachers was Otago’s Phil Bishop, aka ‘the Frog Man’. If you want to know anything about frogs in this country then Phil’s the man to go to 🙂 He kicks off each of his first-year lectures with a ‘frog fact of the day’, & one of these is about the ‘paradoxical frog, Pseudis paradoxa.

What, I thought, could be paradoxical about a frog? Well, it has to do with the size of the tadpoles. P.paradoxa‘s tadpoles are huge: about 25cm long:

Image from

But the adult frog is much, much smaller, at around 6cm long. (And very fetching little frogs they are too.)

That in itself would make a good starter 🙂 But Phil tells his students that Pseudis paradoxa is even more interesting. Like all frogs it secretes mucus that moistens & helps to protect its skin from damage. This mucus contains a protein that researchers have named ‘pseudin-2’, which helps to prevent the skin developing bacterial infections, killing pathogenic bacteria but not harming the frog (or, indeed, human red blood cells when tested on them). This interested Yasser Abdel-Wahab & his colleagues (2008), who tested the action of pseudin-2 & synthetic forms of the protein.

Among other things, they looked at its effect on pancreatic cells in vitro (i.e. growing in nutrient broth in petri dishes), and found that both the natural and synthetic proteins stimulated the cells to release insulin (with no apparent toxic effects on the cells). In fact the synthetic form ([Lys18]-pseudin-2) was more effective in this than the natural form, which has got to be good news for the frogs 🙂 I did wonder what prompted them to test pseudin-2 on pancreatic cells, but it turns out this was no shot in the dark – scientists already knew that peptides released in the mucus of several other frog species affect the function of these cells (Abdel-Wahab et al., 2008).

The research team concluded that [Lys18]-pseudin-2 “may have potential for development as a therapeutically valuable insulinotropic agent for the treatment of type 2 diabetes”, although obviously it’s a long way from trialling something on cells in a petri dish to releasing it as a therapeutic agent.

Maybe there is something in that story about kissing frogs, after all…

Y.H.Abdel-Wahab, G.J.Power, M.T.Ng, P.R.Flatt & J.M.Conlon (2008) Insulin-releasing properties of the frog skin peptide pseudin-2 and its [Lys28]-substituted analogue. Biological Chemistry 389(2): 143-148