The Spider, the Fly and the Octopus: Invertebrate Designs
Small animals without backbones are cleverly designed, leaving evolutionists scratching their heads.
Jumping spiders are “masters of miniature color vision,” Science Daily says. National Geographic put it, “Surprise: Jumping Spiders Can See More Colors Than You Can.” Their eyes are tiny compared to ours, but new research shows that they can see in three color channels, just like human eyes do. Science Daily appealed to Darwin’s bag of tricks:
The “spectral filtering” the researchers discovered had never before been described in any spider. That makes this visual strategy a remarkable example of evolutionary convergence.
Not surprisingly, the paper published in Current Biology had little to say about how evolution converged on trichromatic vision in a little spider, or how this “innovation” came about:
This suggests that a shift from dichromacy to trichromacy may have played an important role in the evolution of the distinctively colorful courtship displays of Habronattus jumping spiders. Future studies will examine if improved color discrimination ability, conveyed by intraretinal filtering, represents a key innovation that enabled the extensive radiation and success of the genus Habronattus.
I.e., stuff happens. Maybe someone will figure it out some day.
In conclusion, our study offers a solution to the long-standing puzzle of how some salticids see color and opens the door for future studies on co-evolution of color vision and coloration. Future work should focus on the taxonomic extent of this filter-based trichromacy, as well as the adaptive benefits most likely to have favored its evolution. In particular, we suggest that trichromatic species may realize significant advantages when foraging in prey communities that include red and yellow aposematic prey.
Australians have been freaking out over “spider rain” (NBC News), but it’s not really raining spiders. It’s the season for their migration. Many species of spiders spin little strands of silk that catch the wind and can transport them long distances. You, too, can freak out. “This is going on all around us all the time,” an arachnologist (spider expert) said. “We just don’t notice it.” National Geographic shows a picture of a piece of ground coated with spider webs like snow. (Not to worry; this poses “no danger to people. It’s a spectacular natural history occurrence.”) It may seem disgusting to some, but the article uses the event to discuss the “Wonders of Silk”—
Silk has been a “huge evolutionary breakthrough,” he said, and “this is one more example of why spiders have been a successful group.“
For a spectacular example of spider coloration and mating displays, see the Peacock Spider dance video embedded in this article at Evolution News & Views. Look how much color and skill is packed into a little guy just five millimeters in size!
A news item in Nature explains how flies use an “internal compass” to build a map of their surroundings. Fruit flies are tiny little guys; they have a compass in their pinheads? Sure; experiments with flies placed into a “virtual reality arena” shows them orienting their heads as they explored the virtual space. Their control traces down to the neurons in their little heads: “Neurons in the central complex showed highly tuned responses that encoded the fly’s orientation relative to a visual cue from the arena.” Once again, though, the explanations resort to speculative processes of convergence in spite of no evidence for evolution:
The possibility that ring-like attractor networks are evolutionarily conserved [i.e., unevolved] raises the exciting prospect that similar internal computational principles are used to calculate orientation in disparate species.
As stated in yesterday’s entry (5/19/15), flies share another “convergence” with humans. Current Biology says, “A recent study shows that brain connectivity in Drosophila melanogaster follows a small-world, modular and rich-club organisation that facilitates information processing. This organisation shows a striking similarity with the mammalian brain.”
A paper in Nature reveals another remarkable correspondence between fruit flies and people: “Together, these results indicate that recursive splicing is commonly used in Drosophila, occurs in humans, and provides insight into the mechanisms by which some large introns are removed.” Recursive splicing is a multi-stage step requiring precise placement of molecular machinery on certain “ratchet points” in the transcribed gene. These ratchet points are “evolutionarily conserved” (unevolved) in the tiny fly’s genes, as to “structure and function”.
An article in Science Daily says that “Ants’ movements hide mathematical patterns.” How did ants learn math? When they go exploring for food sources, they choose “collective routes that fit statistical distributions of probability,” known as Gaussian and Pareto distributions. Surprisingly, these little creatures, unrelated to vertebrates, “converge” again on similar strategies used by higher animals:
Scientists have yet to discover the mechanisms explaining how flocks of birds, shoals of fish, lines of ants and other complex natural systems organise themselves so well when moving collectively.
If they can figure it out, they can share the secrets with robot designers who would love to use the same mechanisms. “For example, they could be used to design the coordination of a group of micro-robots or small robots to clean a contaminated area or other tasks,” one of the researchers said.
Another ant trick shows skill with mathematical physics. National Geographic shows a video clip of a trap-jaw ant using its powerful lightning-fast mandible to fling itself out of a sand trap. “It’s like popcorn. They go bouncing everywhere,” an observer said.
Here’s another ant surprise: they see color really well. PhysOrg says, “their colour vision is likely to be as good as that of humans and old world primates and significantly better than that of other mammals such as dogs, cats or wallabies.” That packs a lot of technology into tiny eyes and brain. It’s so good, robot designers want to learn about microminiaturization from the ants, the article says.
Accompanied by a photo of a brightly-colored weevil, PhysOrg headlines an article, “Within colors of bees and butterflies, an optical engineer’s dream is realized.” Why so?
Evolution has created in bees, butterflies, and beetles something optical engineers have been struggling to achieve for years—precisely organized biophotonic crystals that can be used to improve solar cells, fiber-optic cables, and even cosmetics and paints, a new Yale-led study has found.
Engineers have had a hard time manufacturing the precise geometric patterns at the microscopic scale that produce interference patterns that intensify colors seen in insects. Evolution somehow achieved what intelligent design has been unable to do:
“Arthropods such as butterflies and beetles, which have evolved over millions of years of selection, appear to routinely make these photonic nanostructures using self-assembly and at the desired optical scale just like in modern engineering approaches,” said Richard Prum, the William Robertson Coe Professor in the Department of Ecology and Evolutionary Biology and senior author of the paper.
Honeybee hives are models of collective behavior with social organization, division of labor and economic efficiency. How did that evolve? An article on PhysOrg tries to discern clues in the genes for a phenomenon that has been an evolutionary puzzle for 155 years:
Explaining the evolution of insect society, with sterile society members displaying extreme levels of altruism, has long been a major scientific challenge, dating back to Charles Darwin’s day. A new genomic study of 10 species of bees representing a spectrum of social living – from solitary bees to those in complex, highly social colonies – offers new insights into the genetic changes that accompany the evolution of bee societies.
But do the genes just “accompany” the behaviors, or cause them? That’s a deeper philosophical question. Gene Robinson (U of Illinois) believes they co-evolve: “It appears from these results that gene networks get more complex as social life gets more complex, with network complexity driving social complexity.” So is the unit of selection the gene, or the network? Surprisingly, evolution works against natural selection in this case:
A third major finding was that increases in social complexity were accompanied by a slowing, or “relaxation,” of changes in the genome associated with natural selection. This effect on some genes may be a result of the buffering effect of living in a complex, interdependent society, where the “collective genome” is less vulnerable to dramatic environmental changes or other external threats, Robinson said.
Nature just made a beeline to a special section this week on bees. Here are links to the features:
- Lauren Gravitz writes about bee instincts, their waggle dances, and their “leaderless organization” that creates a “hive mind.”
- Lucas Laursen writes about the “lone ranger” wild bees: solitary bees that are unsung heroes of pollinization.
- Neil Savage writes about bumblebee aerodynamics and the attempts by robot designers to mimic their acrobatic flights. “The flight of the bumblebee is a remarkable feat,” evidenced by the difficulty of playing Rimsky-Korsakov’s virtuouso piece by that name. The tiny hairs on the bee’s body provides sensory data and also dampens aerodynamic forces. Did you know that these champion flyers have been found flying higher than Mt. Everest?
- Alla Katsnelson writes about bee guts. That’s right; “By analysing bacteria that live in the digestive tracts of bees, researchers hope to learn about the role of microbes in insect health.” The bacteria inside bee guts “have evolved to make a living in one of the most extreme antibiotic environments on the planet,” one biologist says.
- A slate of seven entomologists discusses “the biggest challenges faced by bees and bee researchers.”
- Sarah DeWeerdt waxes poetic about “the beeline” – i.e., the “long and interwoven history” between humans and honeybees.
A new glowing millipede in California was announced in PNAS. The title promises to show “the gradual evolution of bioluminescence in Diplopoda,” but once again, the innovation just appears over and over in different organisms. Whether or not it gets brighter over time (in their speculative evolutionary timeline) is a much less challenging question:
Luminescence in Motyxia may have initially evolved to cope with metabolic stress triggered by a hot, dry environment and was repurposed as a warning signal by species colonizing high-elevation habitats with greater predation risk. The discovery of bioluminescence in X. bistipita and its pivotal evolutionary location provides insight into repeated evolution of bioluminescence across the tree of life.
The octopus, a cephalopod (“head-foot”), is one of the most complex invertebrates known, with eyes rivaling the human eye in design, a myriad of complex behaviors, skin that can instantly change color and shape, and eight flexible, highly-maneuverable arms. Another wonder just surfaced: the octopus (and other cephalopods) can “see” with its skin. Science Magazine says that rhodopsin molecules are found in the skin, apparently giving the animals the ability to sense light. (See this ability in an unrelated animal, the brittlestar—an echinoderm, 8/23/01). A press release from UC Santa Barbara says that octopus skin can “see” even without input from the eyes and brain. Though the skin only senses brightness, it’s enough to help the octopus adapt its camouflage quickly, as the embedded video clip shows.
How could this evolve? As usual, the explanation involves innovation and convergence:
According to Oakley, this new research suggests an evolutionary adaptation….
Ramirez wants to understand how these two groups are related. “Do they all come from the same ancestral source or did they evolve multiple times?” he asked.
Science Magazine’s speculation tosses some co-option into the Darwin brew: “light-sensing ability may have originated with an ancestral mollusk, which over time cephalopods have drafted to facilitate their unique behavior.”
Octopus arms are the focus of three recent articles by engineers who want to imitate them for robotics: PhysOrg (“Octopus inspires future surgical tool”), Live Science (“Octopus-inspired robotic arms can multitask during surgery”) and The Conversation (“How we made an octopus-inspired surgical robot using coffee”). Coffee? Kaspar Althoefer explains that their robot uses the same method of “granular jamming” used to pack coffee in cans. “In fact, the granules used in the STIFF-FLOP robot prototypes are actually ground coffee granules because of their excellent jamming behaviour.” It allows the robot to “freeze” the robotic arms in specific positions. The octopus, with its arms always in motion, doesn’t need the caffeine.
Since these three articles were focused on mimicking the octopus’s excellent engineering, they did not venture into speculations about how the octopus might have evolved.
Evolutionists evolve their theories by blind, unguided processes of chance. Creationists reason up their theories by intelligent design.