Welcome back to the Abstract!
You’ve probably been reading a lot about humans this week. Most of the news seems to revolve around humans. Fair enough, we do seem to get up a lot of hijinx.
But now, we’re going to check in on what some other Earthlings have been doing with their time. Some are eating bat poop in the dark underwater caves. Some are getting swole to fight viruses in ponds. Some are literally attracting lightning strikes on purpose. As bizarre as our own antics have been of late, we have nothing on the adaptive genius of our planetary fellows.
Then, once you’ve walked in the shoes (or fins, or branches) of these species, it’s time to get obliterated. Oh, not in a celebratory way. In a torn-into-cosmic-oblivion way. Have fun!
All Hail the Blind Grumpy Poop-Eating Fish Hermit
Sometimes in life, it can seem tempting to retreat from all social activity and hole up in a cave alone for the rest of your mortal existence. I wouldn’t recommend this path for a human, given that social isolation is as deadly to us as smoking 15 cigarettes a day. But solitary life has worked out very well for the Mexican tetra (Astyanax mexicanus), also known as the blind cave fish, which split off from its more gregarious relatives about 20,000 years ago by opting for a quiet life alone in pitch-black underwater caves.
Eyes? Who needs them? Not the Mexican tetra, which navigates instead with lateral sensory lines along its sides. Friends? Nah. More trouble than they're worth. In fact, according to a new study this week, the Mexican tetra is not just an asocial loner, but an actively anti-social curmudgeon—a finding that provides new insights into the benefits and drawbacks of various social structures in the wild.
“The evolution of social behavior in Astyanax mexicanus (AM), which exists as a sighted, surface-dwelling morph and a blind, cave-dwelling morph, provides a model for understanding how environmental pressures shape social behaviors,” said authors Britney Sekulovski and Noam Miller of Wilfrid Laurier University.
“To investigate whether the loss of shoaling in blind AM represents an adaptive strategy rather than a physiological constraint, we examined the shoaling tendencies of surface-dwelling and cave-dwelling AM morphs alongside zebrafish—a well-studied schooling species used as a control,” the team said.
In other words, the researchers wanted to probe whether blind tetras avoid their own kin because they have lost the ability to detect and coordinate with them (physiological constraint hypothesis) or because they simply don’t want to hang (adaptive strategy hypothesis). To assess the difference, the team studied the three species under various laboratory conditions, including when they were hungry, fed, and dosed with prosocial hormones that are analogous to oxytocin in humans.
The results revealed that the “blind cavefish not only fail to form shoals, but actively avoid conspecifics, with hunger further diminishing their social cohesion.” While dosing the blind fish with certain hormones made them slightly more approachable, the findings in total suggest that “the loss of shoaling in blind AM results more from a decrease in their motivation to shoal than an inability to aggregate.” In other words: They just don’t wanna.
Overall, the study validates the hypothesis of adaptive strategy over physiological constraint in explaining the antisocial behavior of blind tetras. But it is also filled with other amazing details about this aquatic introvert and its unusual approach to life.
“Blind AM populations underwent a host of morphological, physiological, and behavioral adaptations…that are believed to have been driven not only by the complete absence of light but also by the lack of predators and extreme scarcity of food in their cave habitats,” note Sekulovski and Miller.
“In such habitats, blind AM feed on low-nutrition organic matter that occasionally drifts into the caves, such as detritus, algae, fungi, bat guano, and the remains of other cave-dwelling organisms,” they added. “Many populations of blind AM, such as Pachón cave populations, are characterized by their relentless pursuit of food and have been suggested to be insatiable.”
Delightfully disgusting diets? Insatiably ravenous? Shunning all light? Truly, these are the fish versions of Dracula. And as the chef’s kiss (performed with guano-tinged fingers), it turns out that the mechanism that drives their eyes to atrophy is named the sonic hedgehog (Shh) gene. What more could you want? The next time you feel like you need some time to yourself, this is the spirit animal to channel.
They Grow Up So Fast (Infected Tadpoles, Obviously)
Tadpoles are incredibly adaptable swimmers that are highly sensitive to their environments. Indeed, scientists have presented new evidence that tadpoles can fight deadly pathogens—like the tadpole-killing ranavirus—by growing much faster to try to stave off infection.
A team studied hundreds of wood frog tadpoles in a sample of Connecticut ponds with different levels of ranavirus load. The results revealed that “tadpoles from Infected ponds were larger at the time of the initial sample and maintained this difference through time,” hinting that the tadpoles in infected ponds can sense they are in a survivalist race against time.
“Our study provides evidence that the presence of ranavirus affects the growth, development, and resource allocation of wood frog tadpoles,” said authors Logan Billet and David Skelly of Yale University. “Specifically, relative to ponds without ranavirus infection, the presence of ranavirus infection in a pond was associated with modest increases in tadpole allocation (size per developmental stage), tadpole growth (size per unit time), and tadpole development (developmental stage per unit time) early in the larval period.”
It’s yet another reminder that tadpoles are blessed with all kinds of inbuilt evasive maneuvers. The study also gets bonus points for the real scientific term “explosive breeders” to describe the prolific reproductive capacity of wood frogs. Imagine being so good at producing offspring, it can only be described as some kind of pyrotechnic denotation. Respect.
These Trees Are in for a Shock
Most living things would prefer not to be struck by lightning. It is, after all, an efficient way to become a dead thing. But it turns out there’s an exception to even this rule: The large rainforest tree Dipteryx oleifera, also known as the eboe, choibá, Tonka Bean or almendro tree, which may have actually evolved to be living lightning rods.
Reaching heights of 130 feet, these trees are not only robust enough to survive direct lightning strikes, they can actually benefit as the bolts kill off competitors and lianas (a type of vine) that infest the trees.
“Lightning strikes are exceptionally powerful phenomena that kill hundreds of millions of trees annually,” said researchers led by Evan Gora of the Cary Institute of Ecosystem Studies. “Here, we use data from a unique lightning location system to show that some individual trees counterintuitively benefit from being struck by lightning.”
The team identified 93 trees that were struck by lightning in Panamas’ Barro Colorado Nature Monument, including nine D. oleifera individuals. All nine survived their strikes with minimal damage, whereas 64 percent of the other tree species died within two years. The strikes on D. oleifera also reduced the number of parasitic lianas infesting their crowns by 78% and killed multiple rival trees around them.
”Not only do D. oleifera trees apparently benefit from lightning, but their unusual heights and wide crowns increase the probability of a direct strike by 49-68% relative to trees of the same diameter with average allometries,” the team said. “These patterns suggest that lightning plays an underappreciated role in tree competition, influencing selection on tree life histories and tree allometries with implications for species coexistence.”
In other words, getting hit by lightning is a spa day for these trees. It’s also a reminder that, though forests seem peaceful, they are actually arboreal combat zones where trees wage war against each other with ingenious weapons. I mean, D. oleifera has learned how to reach up into the sky to deliberately attract bolts of plasma to zap its parasites and rivals. In the immortal words of Werner Herzog, the harmony of the rainforest is a “harmony of overwhelming and collective murder.”
Welcome to the STAR GRINDER
Time to journey to the center of the galaxy. It’s crazy there! There’s a supermassive black hole, called Sagittarius A*, with the mass of four million Suns! It’s orbited by a bunch of smaller black holes, dust clouds, and stars, all in close proximity! We’re sitting out here on the galactic exurbs, but it’s downtown rush-hour all the time around the galactic core. And it turns out the congestion price in this region is death by STAR GRINDER.
Yes, in what may be the most epic term coined this week, researchers proposed the existence of a “star grinder” at the galactic core. This grinder is powered by a speculative population of black holes that were formed from the deaths of massive stars, known as O-type and B-type stars, that are tens of times more massive than the Suns. Stars that enter this region of densely packed black holes risk being torn asunder by the corpses of the old stars (ie. the black holes).
“A population of stellar-mass black holes surrounding Sagittarius A* thus acts like a ‘star grinder’, with any new star being destroyed by collisions with the black holes,” said researchers led by Jaroslav Haas of Charles University. “We find that the collisions of the stars and the black holes can lead to the depletion of the most massive stars…on a timescale of a few million years.”
The star grinder is basically the stellar version of those gorey scenes showing zombies ripping humans to pieces. Life on Earth can seem pretty chaotic at times, but the universe, as always, is great at providing some perspective.
Thanks for reading! See you next week.