Caption

Frog tadpole. Close-up of a two-day-old tadpole of the common frog (Rana temporaria), showing its gills (frond-like, upper left). This is the external gill stage. The gills are feathery and present a large surface for the uptake of oxygen. The head also shows an eye pit (dark spot, upper left). The mouth has not yet broken through but below it is a horseshoe shaped sucker (two bulges, below the head) for clinging to the jelly of the egg sac (not seen). The tadpole feeds on the internal yolk at this stage. At the end of the body is the prominent tail. This tadpole is approximately 10mm long.