biology zoology blog frog egg embryon (1)

A Frog’s Egg

What can a frog’s egg teach us

Hardly anything in zoology could be more exciting than to observe how from an egg cell a whole new individual develops. Unfortunately for the curious person very often the developing egg is hidden from view as in mammals and sometimes it is so small that it is impossible to examine what precisely goes on. But there are some animals which allow even children without the aid of a microscope to observe the embryo and how it grows inside the egg. One example are freshwater pulmonate snails like Planorbarius corneus (the ramshorn snail) or Lymnaea stagnalis (the common pond snail). Their eggs, attached in clusters of up to 40 or so on the glass walls of an aquarium make observations easy. But other, and even bigger and therefore more suitable eggs allowing one to follow the changes that go on inside them are those of frogs, toads and newts. In the gelatinous eggs of these amphibians, rice grain sized in newts but up to the size of peas in frogs, one can see the entire developmental process through the transparent egg membranes virtually with the naked eye (although a hand lens would help, of course).

biology zoology blog toad frog (1)

In Praise of the Toad

In Praise of the Toad – Really?

Few things can annoy me more than injustice, prejudice, unfair treatment and unwarranted accusations. And when I hear comments like “toads give you warts”, I feel sorry for both the falsely accused creature and the ignorant person, who says so. I was really upset when during a practical exercise with live toads one Aussie student bragged laughingly “we used to use them as golf balls”. What a callous attitude towards a living organism! Even if it is as despised as the cane toad, an introduction to Australia from Puerto Rico gone badly wrong as it gobbles up anything that moves and fits into its mouth. —>—>