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A Snail as Fast as a Bullet, and Other Darwin-Defying Marvels

Evolution News

snail

You could fill up a web publication’s daily coverage just with new wonders from the world of life. Would that be expected given Darwinian assumptions? It seems not. Indeed, the closer scientists look at organisms they thought they understood, the more they find bewildering, previously unrealized designs at deeper and deeper levels. 

Here are some seemingly quotidian organisms that have surprised researchers with new tricks worthy of awe.

Fast Snail

Snails and other mollusks are not known for being the quickest animals on the planet, but marine snails known as cone snails are new record setters, according to news from U.C. Irvine. Scientists had already been amazed at the powerful venom of these sea creatures that hunt fish with harpoons. They knew that studying the venom of certain cone snails was providing insight into the causes of pain, such that derived compounds from the animals might lead to new anti-pain medications.

It turns out that cone snails are also lightning fast — not in crawling, but in hunting with their harpoons.

Using high-speed videography, the researchers determined that the radular harpoon can be propelled into prey within 100 microseconds, with a peak acceleration exceeding 280,000 m/s2 and a maximal acceleration exceeding 400,000 m/s2. These extreme speeds are similar to a fired bullet. [Emphasis added.]

The new paper in Current Biology describes the mechanism in the snail Conus catus. 

We report here that the cone snail’s prey strike is one of the fastest in the animal kingdom. A unique cellular latch mechanism prevents harpoon release until sufficient pressure builds and overcomes the forces of the latch, resulting in rapid acceleration into prey. The radular harpoon then rapidly decelerates as its bulbous base reaches the end of the proboscis, a distensible hydrostatic skeleton extended toward the prey, with little slowing during prey impalement. The velocities achieved are the fastest movements of any mollusk and exceed previous estimates by over an order of magnitude.

One of the researchers was curious why this mechanism was so fast, since the fish they prey on are two orders of magnitude slower than the harpoon. He said he wanted “to uncover insights into how they evolve and how their design could inspire new forms for robots or medical devices.” The second goal sounds worthy of intelligent engineering. Good luck on the first goal. Watch this snail at work, if you dare:

Long-Distance Dandelions

Last year, Evolution News reported on a new discovery about dandelions. Each tiny feathered seed, called a pappus, creates a vortex with its tufted plume that actually lifts the seed into the air. The mechanism allows the seed to remain aloft much longer than it would otherwise.

Now, another study by French researchers shows that the arrangement of tufts in the pappus is optimized for lift and flight distance. They created a model using equations from fluid dynamics. The model portrayed rods arranged like spokes on a bicycle wheel, to see how many spokes worked best when air flowed through them. Phys.org says,

The researchers report that their models showed the same kinds of vortices forming as the researchers with the prior effort had seen first-hand. They next ran the models using different numbers of rods. They found that the optimum number was 100, which matched the number found in a real pappus. At this number, the pappus was most stable while floating — with more rods, flight became unstable; with fewer rods, flight distance was reduced. They suggest their findings could be used to design lighter-weight parachutes.

Flashlight Shrimp

The mantis shrimp is already a champion of biomimetic design. Scientists have marveled at its knockout-punching claw, its eyes that can perceive circularly polarized light, and its 16 color channels in vision perception. Now, one species of mantis shrimp has added another curiosity to its bag of tricks: its larvae have flashlights in their eyes. The paper in Current Biology says, “Reflective filters in mantis shrimp larvae simultaneously reflect and transmit light.” The researchers believe this aids the shrimp in detecting bioluminescent targets. 

A video at the beginning of the open-access paper explains how the eyes of these larvae work. It sounds like a description of a high-tech optical invention. The “intrarhabdomal structural reflector (ISR)” is a “four-part, barrel shaped structure,” the narrator says. It contains “hundreds of small round units called vesicles, each about 152 nanometers in diameter, which is the perfect size for interacting with wavelengths of visible light.”

It’s a curious case of reverse biomimetics, researchers at the University of Minnesota indicate:

A University of Minnesota-led research team recently discovered a new way animals can modify their vision. Crystal-like structures in the photoreceptors of larval mantis shrimp simultaneously reflect and transmit light onto light sensitive cells. This newly described structure resembles how a human-made optical device, known as Fiber Bragg Grating, works. Fiber Bragg Grating is a filter commonly used in sensors that monitor extreme conditions for a variety of industries.

“Nature often inspires human design and invention,” said Kathryn Feller, Ph.D., the study’s lead author and a researcher in the College of Biological Sciences at the University of Minnesota. “In this case, humans invented something before they knew a natural analog existed. The structure discovered in mantis shrimp offers a different way to build a useful optical device.”

The scientists were puzzled why only one of 17 families of mantis shrimp possesses this feature. “The big question is what this new larval visual system can tell us about the evolution of adult mantis shrimp color vision, which is the most complex on the planet,” said one researcher. Good luck with that big question, too.

Ecological Hydraulic Engineers

Complete the phrase: “Busy as a ….” 

Metaphors for industriousness, beavers are finally getting the respect they deserve. In America, they were nearly wiped out in the early 1800s to satisfy European men’s vanity for stylish hats. In England, they were decimated, because they were considered a nuisance, leaving fallen trees in their wake. But one can only admire the ability of these large rodents to fell trees with their teeth, drag heavy limbs into streams to build large dams, and create safe houses partly underwater in which to raise their young.

Researchers at the University of Stirling are growing in appreciation for beavers and want them reintroduced in England. They call it the “key to solving freshwater biodiversity crisis.” Beavers don’t just work for themselves. They work for the whole community.

Beavers are one of the only animals that can profoundly engineer the environment that they live in — using sticks to build dams across small rivers, behind which ponds form. Beavers do this to raise water levels to avoid predators, such as wolves and bears: however, numerous other plants and animals also benefit from their work.

Comparing 20 wetlands in Sweden, half of them without beavers present, the researchers found much richer animal and plant diversity in the beaver-engineered environments. Everyone from small beetles to large mammals benefited from the wetlands created by beavers. 

This research follows the team’s 2018 study that found that 33 percent more plant species and 26 percent more beetles were living in wetlands created by beavers, compared to those that were not. Another previous study, from 2017, showed that — over a period of 12 years — local plant richness in a Tayside wetland rose by 46 percent following the introduction of beavers. They created 195 metres of dams, 500 metres of canals and a hectare of ponds.

Desalination Plants

Toss some water lilies into those beaver ponds, too. The un-wettable surfaces of their leaves have inspired super-hydrophobic materials in previous studies. Now, a team publishing in Science Advances took inspiration from water lilies to conceive of a new way to get fresh water from salt water. Previous designs typically clog up the mechanisms with brine. How does the humble water lily keep its leaves so pristine?

Water lily naturally (Fig. 1A) has an elegant system of transpiration with several features. First, the upper epidermis absorbs sunlight and provides stomata for water vapor escape. Its well-known hydrophobic surface has self-cleaning property. Second, the water lily can float naturally on the surface of water because of the existence of lacunae (air chamber) at the bottom of the leaf. Third, there exists a confined water path provided by vascular bundles to pump up water and then spread it into the large surface of the water lily. Taking advantage of these features, we propose a water lily–inspired hierarchical structure (WHS), which can realize highly efficient, stable solar evaporation in high-salinity brine/wastewater until complete separation of water and solute is obtained.

In biology, intelligent design is a gift that keeps on giving. When approaching the workings of plants and animals with design in mind, scientists keep finding new layers of wonder behind the first impressions that inspired them. These brief examples from cone snails, dandelions, mantis shrimp, beavers and water lilies promise that biologists and engineers will never run out of clever ideas to imitate in the millions of species that inhabit our planet.

Photo: A Conus catus shell looks pretty harmless, but do not be deceived, especially if you are a fish, by Philippe Bourjon via Wikimedia Commons.