Animal Magnetism and Other Wonders
What is it that so attracts us to animals? Is it animal magnetism? Some animals do have magnetic senses that can guide them across oceans. The more we learn about animals, the more we should admire their high-tech equipment. Here are some recent examples of amazing animals, some of them suitable for Halloween decorations.
Eensy weensy wonder spider: After cockroaches, spiders are the second most vibration-sensitive creatures, reported PhysOrg. Researchers at the University of Vienna used scanning white light interferometry and micro-force measurements to measure the strain sensors on a species of wandering spider that detects vibrations on leaves to detect prey. Strain sensors? Yes. Here’s how they work: “Team member Friedrich G. Barth explained that the spider has over 3,000 strain sensors in its body, mostly on the legs and in vibration receptors located near the leg joints,” the article said. “Each strain sensor comprises a series of arrays of tiny parallel slits in the compound lyriform [lyre-shaped] slit sense organs that detect vibrations and movements. When forces are applied the slits are compressed and stimulated.” And that’s not all: spiders can see in the dark and sense odors on their antennae. Remember that when you see spider decorations for Halloween.
Giant spider webs: Some spiders can cross rivers with their giant webs. The species Caerostris darwini, endemic to Madagascar, builds “the largest known orb webs utilizing the toughest known silk.” PLoS ONE reported findings of a team who studied the web-building activity of these spiders that were just discovered last year (9/24/2010). The webs of C. darwini are made of silk combining strength and great elasticity such that it outperforms all other known spider silks, and even most synthetic fibers, in terms of toughness (work required to fracture the silk),” the researchers said; “Furthermore, capture areas of C. darwini webs regularly exceed 1 m in diameter and are suspended on bridge lines that often exceed 10 meters, while the largest capture areas reach almost 2 meters in diameter and are suspended on bridge lines up to 25 meters in length.” The team wanted to know how the spiders manage to bridge such large distances, and whether the silk toughness co-evolved with this ability. They watched 32 spiders in action. The spider starts by spinning a “bridging silk” that consists of several strands that catch the wind then recombine within 24 seconds into a line that gets tangled in vegetation across the stream. The spider then “reels in” the bridging line, from which it can travel out and start constructing its large orb web above the water. It drops a vertical line in the center, forming a T structure, from which it creates diagonals up to the bridge line, resulting in a triangular web. Within hours, the web is complete. Curious readers may wish to visit the open-source paper for details how the spiders build their world-record webs. The authors could not do more than speculate on how their specific adaptations evolved. Citation: Gregorič M, Agnarsson I, Blackledge TA, Kuntner M, 2011. How Did the Spider Cross the River? Behavioral Adaptations for River-Bridging Webs in Caerostris darwini (Araneae: Araneidae). PLoS ONE 6(10): e26847. doi:10.1371/journal.pone.0026847.
Glow in the dark: What could be spookier than eerie green lights in the dark? Biological light – bioluminescence – is common among marine and land animals. Among glowing sea creatures are tiny unicellular animals living in surface plankton called dinoflagellates. They give rise to the “red tide” under certain conditions when they bloom in large numbers. During red tides, night-time beachgoers can see the waves glowing with a spooky blue-green light, and every step on the wet sand produces a hundred sparkles. An explanation for how these tiny organisms scintillate when mechanically stimulated was reported on Science Daily. Here’s how the article described the “novel mechanism” that produces a “beautiful natural phenomenon in our oceans”—
As dinoflagellates float, mechanical stimulation generated by the movement of surrounding water sends electrical impulses around an internal compartment within the organism, called a vacuole–which holds an abundance of protons. These electrical impulses open so-called voltage-sensitive proton channels that connect the vacuole to tiny pockets dotting the vacuole membrane, known as scintillons. Once opened, the voltage-sensitive proton channels may funnel protons from the vacuole into the scintillons. Protons entering the scintillons then activate luciferase—a protein, which produces flashes of light, that is stored in scintillons.
Ghost sense: An article on Science Daily is permeated with evolutionary speculation, but the observational part is cool. Many species of “primitive” fish, including sharks, paddlefishes and certain other aquatic vertebrates, have the ability to “detect weak electrical fields in the water and use this information to detect prey, communicate and orient themselves.” Readers can judge whether they buy the claim that humans evolved from a common ancestor with this sixth sense that lived hundreds of millions of years ago, but it is remarkable that any animal would have electroreception organs and the brain power to use that information.
Cookie cutter cats with steak knives: PhysOrg had an interesting article about the extinct sabre-tooth cats that once roamed North America, Europe and Asia. Fierce hunters, some were large, sleek animals, some with bodies like cheetahs equipped for pursuit, and others (like California’s Smilodon, found in the La Brea Tar Pits) were more muscular, like bears. Facial adaptations, such as larger lips and jowls than seen in modern cats, added to their abilities. Virginia Naples of Northern Illinois University, who owns two cute tabby cats, has a fascination with the large sabre-tooths. With her colleagues, she has published a new book updating what is known about the various species. One species they dubbed the Cookie-Cutter Cat “for its ability to chomp a large, clean chunk of flesh from its prey.” It sported serrated biting teeth 3.5 inches long. “It had a whole mouthful of steak knives,” Naples said. Happy Halloween.
Unerringly across the sea: Among the animals that use the Earth’s magnetic field to navigate (e.g., birds, Monarch butterflies, sea turtles), inherited instructions somehow allow the creatures to find their targets without ever having seen it before (for a detailed description of the Monarch butterfly migration, see the new documentary Metamorphosis). In the latest edition of Current Biology (21:20, R843-R846, 25 October 2011, doi:10.1016/j.cub.2011.09.002), Thomas and Matthew Collett explored how loggerhead turtles follow “signposts in the sea” to navigate their large oval circuits. In the lab, scientists can alter the hatchlings’ swimming orientation with magnetic fields. Out in the ocean, hatchlings mature for a few years in the Sargasso Sea, but then must migrate back to the Florida coast; fortunately, “hatchlings come equipped with instructions to provide this active navigation,” the authors said. When scientists play a cruel joke on them (in the name of research) and put hatchlings far north near the coast of Greenland, they don’t know what to do. Older individuals, however, can calculate the difference between actual and expected, and find the way back. “The technique of teleporting turtles and other animals to magnetically defined places, which works so well for understanding the turtles’ inherited routes, is also revealing map-like navigational strategies in older individuals that have learnt or become imprinted on particular locations.” Similar behaviors have been observed in red spotted newts and lobsters, the authors said.
Rudolph’s coat: Halloween’s passing means Christmas is not far away, with its iconic images of reindeer. Real reindeer may not fly, but have some cool tricks for maintaining body heat. “Insulated in a luxuriously thick winter coat, reindeer are perfectly prepared for the gripping cold of an Arctic winter, PhysOrg reported. “But the pelt doesn’t just keep the cold out, it keeps the warmth in too: which is fine when the animals are resting….” Problem: Rudolph has to bolt through the snow when Santa cracks the whip. His body temperature soars. Now what? A Norwegian scientist figured out three strategies the reindeer uses: “panting with their mouths closed to evaporate water from the nose; panting with the mouth open to evaporate water from the tongue; and activating a cooling system that selectively cools the blood supply to the brain.” Like dogs, reindeer have large, wet tongues good for evaporative cooling. Problem 2: How does Rudolph coordinate the three methods? Norwegian scientists took measurements by playing Santa and exercising their cooperative deer, and found that “reindeer use… a heat exchanger when their temperature becomes dangerously high”. Heat exchanger? Yes; “They began selectively cooling the brain by diverting cooled venous blood – which came from the nose – away from the body and up into the head, where it entered a network of heat exchanging blood vessels to cool the hot arterial blood destined for the brain to protect it from overheating.” By inhaling colossal amounts of cold air, the article explained, “reindeers were able to inhale sufficient cold air through their noses to keep their brains cool, but only as a last resort once the other cooling tactics were no longer sufficient.” And that is how heavily-coated reindeer keep their cool.
There’s no end of wonders to study in the biological world. How did they come to be? By random, purposeless, directionless processes? A reindeer needs all those strategies in place to survive a lengthy escape from a predator. Turtles without navigation will never make it home to lay eggs. Spiders without strain sensors and dark-adapted eyes could not eat. Even the tiny dinoflagellates have irreducibly-complex systems to produce their mechanically-induced sparkles.
Mutations are almost all harmful or neutral. Beneficial mutations, almost unknown in genetics (the controversial examples often with damaging pleiotropic side effects) could never accumulate fast enough to create any of these abilities described above. The Creator put into each animal the initial equipment to thrive and the genetic ability to adapt to changing environments, such as those encountered by the Madagascar spiders (no credit to Darwin). An environment cannot create an adaptation any more than a mountain can create a mountain climber. Let’s rid ourselves of evolutionary myths and face the facts of nature with humility and wonder. Science should be a treasure hunt. Kick the useless storytelling charlatans off the field, and let’s go hunting!