July 16, 2021 | David F. Coppedge

Life Exceeds Expectations: Invertebrates

Here are examples of terrestrial invertebrates
that exceed the requirements for survival



Froghoppers able to suck with enough force to draw up liquid in a vertical straw 100m long (Phys.org). Froghoppers are tiny insects that are known for their remarkable ability to leap over tall buildings (at their scale; 100 body lengths) with a single bound. They leap so fast, they almost disappear from view (see 20 April 2018). Now they have another superpower: sucking strength. Froghoppers suck on xylem water that has negative pressure in the plants they prefer, requiring them to exert sucking force to reach it. Researchers at the University of British Columbia measured the force:

To find out just how much suction froghoppers can generate, the researchers captured multiple samples and studied them in their lab. First, they took micro-scans of the heads to learn about their structure. They found that the insects had a cibarial pump in their foreheads—it works much like a diaphragm when it is pulled by muscles. In froghoppers, that Amazing Factsmuscle is called the post-clypeus and it turned out to be very large for an insect. The researchers then used the dimensions of the pump and muscle to calculate how much force the two working together could generate—approximately 1.6 megapascals. This negative pressure force, the team notes, is greater than the negative pressure exerted by the plants that generate the xylem sap. They note the force is strong enough that the little insect could suck the water out of a cup at the base of the Statue of Liberty while perched on its crown.

Sucking water all day creates an issue for the froghoppers. It makes them have to urinate a lot. No problem; they just catapult it away, the article says. “They also have a butt catapult that throws their urine through the air to keep the bugs from being overwhelmed because they pee so much,” Bob Yirka writes humorously. “And now it seems they are also champion suckers.” For details, see the paper by Elisabeth Bergman et al. in the 14 July 2021 Proceedings of the Royal Society B.

Beetles make ‘Teflon’ to grease their knees (Nature). It’s slicker than Teflon. Beetles need to lubricate their joints, too, but they have a problem: unlike vertebrates, who have enclosed joints, insect joints are exposed to the air. Scientists at Christian-Albrechts University of Kiel in Germany found that the darkling beetle manufactures an amazing lubricant made out of proteins and fatty acids. The grease oozes out of pores in the joints.

When the authors compared this grease to other lubricants experimentally, they found that the substance reduced friction to a similar degree as the chemical coating Teflon. They also found pores and lubricant in the joints of several other species of beetle and a wood roach.

The lubricant is made of protein and fatty acids. That means it must be translated from genetic code and built inside ribosomes in cells. Then it has to be transported to the right location for use. It will be interesting to learn how the pores form without interfering with the action of the joints, and how the substance is secreted. Perhaps this will turn out to be an engineering design found universally in insects. If so, it might find application in nanotech machines that need to stay well lubricated.

How spiders distinguish living from non-living using motion-based visual cues (Science Daily). It’s a remarkably human skill for an invertebrate: the ability to tell the difference between animate and inanimate objects. Humans and other vertebrates can pass tests of this ability with “very limited visual information, such as a point-light display, which shows dots representing the positions of the main joints.” Jumping spiders have 8 eyes arranged around their heads; do they have this ability, too? Sixty spiders tested by Harvard researchers had a counter-intuitive response: they turned their primary eyes toward randomly-blinking dots instead of those simulating biological organisms. There’s a reason, the researchers figured:

“Jumping spiders’ secondary eyes confirm themselves to be a marvelous tool,” the researchers add. “In this experiment, we observed how they alone can tell apart living from non-living organisms, using the semi-rigid pattern of motion that characterize the formers and without the aid of any shape cue. Finding the presence of this skill, previously known only in vertebrates, opens up new and exciting perspectives on the evolution of visual perception. My co-authors and I can’t wait to see what other visual cues can be perceived and understood by these tiny creatures.”

The open-access paper about this ability can be found in the July 15 issue of PLoS Biology. But what does evolution have to do with it? (see 1 July 2021, “‘The evolution of’ is a useless phrase”). Applying Darwin Flubber, the article asserts,

Complex vision evolved independently in vertebrates and arthropods and so the ability to distinguish living from non-living motion using the relative positioning of the joints has most likely arisen convergently in the two groups of animals.

Such reasoning, though, relies on a prior commitment to evolution. Otherwise it would “most likely” point to common engineering principles (12 June 2021) for very different creatures that have similar needs.

In his book Twenty Evolutionary Blunders, Dr Randy Guliuzza rightly fingers the term “convergent evolution” as a product of imagination. “Convergence is not an observation flowing from objectively discernible causes,” he says on page 63. “It is actually a declaration based on mental pictures of diverse organisms evolving similar traits as they are shaped over time by alleged similar environmental pressures.”

See also Brett Miller’s excellent treatment of “The Convergence Concoction” at his site EvidentCreation.com. As for complex eye evolution evolving independently, see his detailed and well-illustrated articles on Eye Origins, Part I and Part II.

After we have sucked the Darwin Flubber out of these stories, we can marvel at the abilities the Creator has given to froghoppers, beetles, jumping spiders and millions of other invertebrates. Our awe comes directly from the observations, not from mental pictures of creatures evolving.


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