What I Learned Today

There is a female frog that swallows its eggs to protect them from predators until they mature. Once swallowed, the eggs secrete a substance that inhibits the production of hydrochloric acid in the frog’s stomach and halts normal muscular contraction that shifts food through the stomach and into the gut. Effectively, the frog’s digestive system turns off for six weeks for this “gastric pregnancy”. Not only that, the baby frogs get so big that they compress the female frog’s lungs, and for the last part of this experience she has to breathe through her skin instead. Imagine her relief when the frogs finally emerge from her mouth. (Photo by Mike Tyler)

This and other ultra-fascinating facts are to be found in David Attenborough’s book, “Life in Cold Blood.” I’ve only read the first chapter (on amphibians) so far, and literally every page has some interesting new fact on it. Not only that, but it is chock-full of gorgeous pictures of the animals being described. They’re all so interesting and alien that I’m nearly moved to get an aquarium and populate it for the observational opportunities.

Did you know?

• Some fish (e.g., lungfish) have primitive lungs (simple pouches lined with blood vessels) and can breathe air.
• The great crested newt lives out of the water, in damp regions, returning to the water to breed. Their eggs lack pigment to protect them from UV, so the female individually wraps each egg in a plant leaf with her hind legs (she lays 2-3 every day from March until mid-July! Talk about unending labor!).
• Many salamanders in the northeastern US have lost their lungs and breathe entirely through their skin, developing long tails that increase their surface area relative to their volume.
• Caecilians somewhat physically resemble earthworms, though they are amphibians. They burrow, and they’ve become sightless, although they do still have eyes — they’re just covered by skin. They are carnivorous, and in some species the female rears her young by repeatedly growing an outer skin, letting them nibble it off, and then resting and regrowing the skin. You can actually watch a video of this from the BBC’s Life in Cold Blood show. Wow, they’re tough! (Never go in against a Caecilian…)
• Different frog species may only be able to hear certain frequencies, which correspond to their own vocal range, so that they need not be confused by the cacophony of other species.
• The transformation from tadpole to frog is, really, simply miraculous. It is an herbivore as a tadpole, with a long coiled gut to permit digestion of plant matter. It grows front legs inside its gill chamber which then burst out fully formed on the sides, it develops lungs, its gut shortens and it becomes a carnivore. It basically completely reconfigures itself for an adult life in an alien environment, with alien food and a different means of mobility required.

I’m even more in awe, at the diversity and innovation of life on our one single planet, than I was before opening this book.