Biomedical Ephemera, or: A Frog for Your Boils

Lepidosiren aimectans [now Lepidosiren paradoxa] - South American lungfish

This curious Amazon-basin fish is one of the few obligate air-breathers in the fish world, meaning it cannot get its oxygen from the water it lives in, and must breathe from the surface. It’s also notable in the ichthyological world for being a hibernator when conditions are poor, much like frogs and toads. It can encase itself in a cocoon of mud, and re-emerge as much as 6 months later, having had no fresh air or water in the mean time.

The first naturalists to encounter these fish in the mid-19th century recognized that when they dissolved these mud-cases underwater, the encased fish would “come back to life”, but they assumed that the mud casing was a very short-term protection capsule for the fish.

When they took the capsules back to Europe and dissolved them, assuming they would get some dead (but preserved) specimens, the lungfish took more than one group of zoologists by surprise when they sprung back to life, even after a 3-month voyage over the Atlantic.

South American lungfish behavior hasn’t been as well-studied as African lungfish behavior, but their hibernation/estivation behaviors are very similar. However, the South American lungfish is not believed to be as capable of crossing land as African lungfish, owing to its smaller “limbs” and its very swampy environment - African lungfish tend to live in ponds with defined shorelines, rather than swampland.

Popular History of the Aquarium of Marine and Fresh-Water Animals and Plants. George Brettingham Sowerby, 1857.