Metamorphosis

Armed with a net and bucket, we headed off to sample some dam water among the rushes to see what waterbugs were present. Sifting through the sample, we discovered a variety of little darting creatures: tiny water mites, beetles, backswimmers, waterboatmen etc. – as well as a few tadpoles, which we took back to the house to examine.

With the aid of our newly-acquired copy of Marion Anstis’s superb book Tadpoles of South-eastern Australia, a hand lens, a USB microscope and camera, we endeavoured to find out which species they were.

Tadpole identification is not easy, and requires the careful study of a range of features such as body/tail shape and size, location and arrangement of mouth parts, eyes and nostrils, pigmentation and many more. These features are used to work through a scientific key to hopefully arrive at the correct identification. Use of the key requires beginners like us to learn a whole new glossary of terms, such as flagellum, iridophores, nares, papillae and spiracle.

The amazing metamorphosis from egg to frog, which can take months, has been divided by biologists into 46 developmental stages. The tadpoles we found seem to be of two or perhaps three species and were fairly well developed, with almost complete mouth parts and hind limbs emerging.

With little confidence we decided that the tadpoles we had would develop into Plains Brown Tree Frog (Litoria paraewingi) or Whistling Tree Frog (Litoria verreauxii), which have fairly similar tadpoles – and Pobblebonk, aka Banjo Frog (Limnodynastes dumerilii). We know from their calls that all of these frogs frequent the dam, but clearly we need more practice in tadpole ID!

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