It is difficult, and yet important, to practice holding multiple truths at once, such as: No animal is inherently bad, and also the Surinam toad is a toad of nightmares. The diversity of life on Earth should be celebrated, and also the Surinam toad’s particular eccentricities are satanic. Every living thing is beautiful because it is alive, and also the body of theSurinam toad is an affront to beauty itself.
The Surinam toad, which has the dissonantly cute scientific name Pipa pipa, is an aquatic frog that lives in the murky, tannin-dyed waters of the Amazon and Orinoco rivers and tributaries in South America. You might not have heard of the Surinam toad by name, but you have probably seen it in images circulated on the internet that highlight its most peculiar evolutionary adaptation, which is the toad’s ability to give birth through its back. Most toads lay eggs in the water that hatch into wriggling, boba-bodied tadpoles. Not the Surinam toad. After she lays her eggs in the water, the male will fertilize them and then push them onto her back, where she will grow a new, thick layer of skin over the eggs until they appear studded in her back like big blackheads waiting to be popped. There the babies grow until they are toadlets, at which point they spurt from their mother’s back like fat gobs of sebum. If you would like to witness this miracle of life, you may do so at your own discretion.
Once freed, the toadlets jet off and grow up. The adults are extremely flat and have no tongue. They spend their days lurking like a corpse in the brown water with their big hands outstretched like Mr. Mime. When a tasty morsel swims close by, the toads open their enormous mouth to vacuum in their prey and swallow it whole. It is an oddly impressive feat for such a flat frog.
Now, a new paper in the Journal of Comparative Physiology A explains how the toads sense their prey in such murky conditions. The secret rests in the toad’s fingers, which almost have fingers of their own. Although everyone is understandably fixated on the frog’s strange back, its hands are also strange. The toad’s four fingers each sprouts into four little lobes, which you can admire in this rather elegant, even yearning photo of a Surinam toad hand.
But that’s not all! The tip of each of these four lobes sprout into four even tinier lobes, meaning each frog finger has a bouquet of 16 tiny lobes, like so. This totals to 128 mini-lobes per Surinam toad. Please enjoy this extremely zoomed-in photo of these little lobes in the photo below, which are colored for your viewing pleasure.
Duncan Leitch, a neurobiologist at the University of California, Los Angeles and an author on the paper, learned about the toad’s little lobes from an anatomy paper. “It immediately seemed to me like these lobes might be somewhat analogous to antennae that the frogs extend so they can feel the space around them,” he said in a press release. When the researchers scanned the frog’s fingers under a microscope, they found each lobe was downright knobbled in sensory bumps called papillae, the same sensitive bumps that carpet our tongues. And when the researchers anesthetized the frogs and touched different parts of their fingers with tools designed to deliver precise forces, they found the fingers were most sensitive to touch at their tips, just like our fingers. They also measured the frog’s nerves and found the little lobes contained 60 percent of the touch-sensitive nerves in each arm.
The best comparison for the toad’s fractal fingers might be the star-nosed mole, which has 22 fleshy nasal tentacles riddled with sensory organs. These organs are known as tactile fovea, and they give the moles an extraordinarily detailed understanding of the world around them. The mole devotes a huge amount of its brain space to its star and the tactile information it collects: around half its cortex, the wrinkled outer layer of the brain. Although the Surinam toad does not have a cortex, it processes its sensory information in a part of the midbrain called the optic tectum. And even though its 128 lobes are such a tiny fragment of the frog’s body, they occupy an outsized amount of the frog’s brain. If you’d like to visualize this, please enjoy this only moderately horrifying illustration of a Surinam toad that depicts its toes as if they were proportioned according to the amount of space they take up in the frog’s brain.
The researchers also observed Surinam toads hunting bluntnose minnows in a lab. As the toads lurked at the bottom, they managed to slurp up prey that came within a half centimeter of their splayed fingers, suggesting the toads were indeed using their little lobes to sense movements in the water. The frogs do have eyes, but they are extremely tiny and situated on top of their head and offer little help in the way of detecting prey with any kind of precision. When it comes to hunting, it’s all about the fingers.
Two things can be true. The Surinam toad’s body, at least to me, embodies a kind of anatomical dystopia whose process of childbirth makes me want to shut my eyes, and whose hands recall a polydactyl AI hallucination. And also the Surinam toad is a testament to the fact that evolution has no obligation to beauty or moral sensibility, and clearly the frog is doing fine. In fact, it is thriving, hailing from a family of frogs that dates back to the Cretaceous. And when the Surinam toad rests its wretched body on the floor of some brown stream and stretches out its long and discomfiting fingers, it feels the ripples and waves of the water more exquisitely than we could ever imagine.