Mus muscularis. Photo by G. Shutlin, Wikimedia Commons
(To listen to an audio version of this blog, click on the following link….Mouse hairs, octopus brains and talking mushrooms
Recent articles in The New York Times and The Scientist described a paper written by a British defense industry physicist, Ian Baker, whose research area is infrared sensors. The paper (published in the December 8, 2021 issue of the Royal Society Open Science) described the extensive infra-red observations Baker made on the nighttime behaviors and activities of animals living in the diverse field and wooded habitats near his home. Using his highly advanced infra-red cameras, he observed numerous small mammals (including a number of species of mice, shrews, voles, squirrels, hares and rabbits) and also several of their predators (specifically, domestic cats and barn owls).
Figure by I. M. Baker. R. Soc. Open Sci. 8, 210740
Baker noted that the cats and barn owls seem to assume quite exaggerated body positions when hunting for and lunging at their prey. These body positions (the cats hunched back behind their cold noses and the owls twisted and folded up to hide their faces and legs) seem, on Baker’s outstanding thermal photographs, to function to conceal the heat signature features of the predator’s body from their prospective prey. Baker wondered why they would be doing this?
Infrared sensor-like hairs of the common shrew. Figure by I. M. Baker. R. Soc. Open Sci. 8, 210740
Baker then examined the microscopic structure of the guard hairs on the backs of diverse group of potential prey species and found a curious, but very consistent feature: the hairs all had regular arrangements of bands of pigments along the length of their shafts. Further, this band pattern was quite familiar to Baker: it was the same banded pattern found in his own thermal sensors that were tuned to specific wavelengths of electromagnetic (EM) radiation! Specifically, the band pattern in these guard hairs were identical to those in thermal sensors designed to detect EM radiation with wavelengths of 10 microns. This wavelength is in the mid-infrared region and is also the most typical infrared heat signature of a mammalian or avian body.
Baker hypothesizes that the banded guard hairs on his mice, voles etc. are in fact sensory receptors designed to detect the infrared body signature of an approaching predator. If this hypothesis is correct, then these prey species have a “360 degree sensory shield” that helps to protect them from predators. More research is called for to examine the neural connections of these guard hairs to determine if, indeed, they transduce heat signals into sensory nerve impulses.
Day octopus, Photo by M. Tattersail. Flickr
I have written about the intelligence of octopuses and other members of Class Cephalopoda before (see Signs of Summer 1, June 3, 2021). Many lists of the “most intelligent animals” put octopuses among the top ten most intelligent organisms in all of Nature! They are typically ranked as being more intelligent than dogs or cats, but slightly less intelligent than chimpanzees, orangutans, elephants or dolphins! They are, without question, however, the most intelligent, group of invertebrates on Earth! Octopus brains, though, have not been extensively studied using some of the newest tools of neurobiology.
On average, octopus brains contain a little over 500 million neurons! That’s comparable to the number of neurons found in a dog’s brain. It is possible, though, as I mentioned in my June 3, 2021 blog, that due to the incredible diversity of types of cellular junctions seen in octopus neurons, that the octopus neuron-network is more both more efficiently and more complexly interconnected than those found in mammalian species with comparable numbers of neurons.
Vampire squid, Photo by MBAR, Wikimedia Commons
A research team at the University of Queensland (Australia) Brain Institute explored the brain anatomy of four cephalopod species using advanced Magnetic Resonance Imaging (MRI) technology. Their results were published in the November 18, 2021 issue of Current Biology. The selected cephalopod species were from a broad range of habitats and exhibited a number of different behaviors and ecological roles. The organisms in the study included the vampire squid (Vampyropteuthis infernalis) (a deep ocean species), the blue lined octopus (Hapalochlaena fasciata) (a solitary, nocturnal species), the algal octopus (Abdopus capricornicus) and the day octopus (Octopus cyanea) which are both diurnal species found in complex, species-rich reef ecosystems.
The findings of this study were quite logical, but also quite elegant. The optic lobes of the brains in the vampire squid and the blue lined octopus were much smaller and less complex than the optic lobes in the algal and day octopuses. The importance of vision and visual memory in these two diurnal predators was clearly correlated with their MRI’s. Also, the vertical lobes of the algal and day octopuses were larger and more complexly folded than either the vampire squid or the blue lined octopuses. The vertical lobe is involved with memory and learning and undoubtedly helps these two, diurnal octopuses develop and carry out complex tasks both in hunting for prey and avoiding becoming prey for other, larger predators.
This study clearly correlated the ecological roles and requirements of these cephalopod species with the development and evolution of their complex brains. There are about 800 living cephalopod species doing all sorts of activities in their very diverse environments. Let’s hope that neurobiologists continue to explore these as yet unexamined brains in order to generate a more complete picture of the evolution of invertebrate intelligence!
Forest mushroom, Public Domain
I have written about fungi before (Signs of Spring 10, May 3, 2018). I have looked at fungi from an ecological point of view discussing their ability in soil ecosystems to form mycorrhizal, symbiotic networks with plant roots that enable plants to more efficiently gather nutrients and the fungi to gather energy molecules from the plants. I have also talked about the chemical diversity of fungi (and especially their mushrooms) and some of the research exploring the use of these chemicals as medicinal drugs to benefit human health. I have also talked about gathering wild mushrooms for food (and fun!). A recent research paper, though, in the Royal Society Open Science (April 6, 2020) explored a feature of fungi that I didn’t have any idea existed: how they “talk” to each other!
Fungal hyphae mass. Photo by S. Thimmiah, Wikimedia Commons
Fungal hyphae (the long, thin, cellular “threads” that a fungus forms as it grows through its environment) make interconnections with other fungi and also with plant roots. The Fungus/plant interconnections are the mutualistic mycorrhizae mentioned above. Hyphae are capable of generating electrical impulses similar to the action potentials seen in nerve fibers. Researchers at the Unconventional Computing Laboratory at the University of the West of England used micro-electrodes to monitor the hyphal electrical impulses of four common mushrooms (enoki, split gill, ghost and caterpillar fungi). Their observations suggest that the electrical impulses being produced by these fungi are not random by-products of some other metabolic processes. Instead, there were distinct patterns to the impulses that suggested an organized “vocabulary” of some 50 “words!”
If these electrical impulses are, indeed, words, what could these fungi be talking about? What information would be so valuable to a community of fungi that could account for the large metabolic expense required to both run and recover from these electrical cascades? What natural selection system could explain the elaborate, evolutionary steps and sequences required to construct these electrical generating systems?
Can we expect to be able to translate these fungal “words” into a human language? Would they make any sense to us at all? Probably not. As the philosopher Ludwig Wittgenstein put it, “If a lion could speak, we could not understand him.” And, a fungus is much more alien to us than a lion!