There's a frog in my tadpole
Sometimes a photograph can instantly give you a whole lot more information on a topic than you ever knew.
This is a cropped close-up of a picture that I showed on the blog a few weeks back (see here). At the time that I took the picture, and later when I selected it for the blog post, I had completely failed to spot this metamorphosing frog in the image. I had never fully appreciated how the new frog in a metamorphosing tadpole was formed. Perhaps because of the colour of this Xenopus laevis frog from an invasive population in Tucson, Arizona, is so stark, you can clearly see through the transparent tadpole flesh the form of the frog coming through.
Note how the head of the tadpole and head of the frog appear to be completely different, yet the sensory organs (eyes, nares, etc.) are functioning on the tadpole and joined by nerves to those same sites on the frog head. Note also the way in which the fore-limbs (that always appeared to come at an odd place on the tadpole) are perfectly situated in relation to the frog head.
Over the next week or so, the tadpole head will regress in size and the tail will start to shrink as the final stages of metamorphosis take place. Sensory organs will relocate into the frog head.
