My desk top
(Click here to listen to an audio version of this blog!)
I get ideas for blogs either from my own observations out in nature or from reading about observations in the scientific literature. I keep file folders open on the desktop of my computer, and when I come across an interesting article in one of the publications I read, I add to one of the files. When I get enough articles about a particular topic or when I see some connections between articles on somewhat different topics, I do some extra background reading to flesh out the ideas and then write about the articles.
Sometimes, though, there are articles that just don’t fit together with any other articles. They are often strange, wonderful, esoteric bits and pieces of research that deserved to be noticed and discussed, but by themselves wouldn’t rise to the typical 1200 + word length of these blogs. Today, though, I am going to talk about four of these unique articles that have been hanging around for a while on my computer. Here are some “short-blogs” for our Signs of Summer #1!
Two miles below the Earth’s surface
(this is from an article that an old student of mine, Chris Urik, called my attention to. Thanks, Chris!)
Sunrise dam open pit gold mine. Photo by Calistemon. Wikimedia Commons
Gold mines are the deepest human-made holes on Earth! One of these deep holes, the Moah Khotsong mine in South Africa, extends more than two miles below the Earth’s surface, and the rocks at the bottom of this mine are three billion years old! Water can get trapped in pockets and spaces in these deep rocks and become sealed off from any contact with the surrounding environment for many thousands of years. Recently, scientists sampling these hidden micro-pools found to their great surprise complex, living organisms inhabiting them!
Halicephalobus mephisto. J. Bracht. Wikimedia Commons
For example, in one water pocket that was dated to be five thousand years old a new species of nematode (called Halicephalobus mephisto) was found. This deep dwelling worm is 0.5 mm long and survives by feeding on chemosynthetic bacteria that form biofilms in the 37 degree C (99 degrees F) water. Halicephalobus mephisto’s genus name means “he who loves not the light” in Greek, and its species name is from the devil, Mephistopheles, in the legend of Faust. Popular news stories about this new nematode have referred to it as the “devil worm.”
Three other species of nematodes have also been described from these deep, rock water pockets along with flatworms, segmented worms, rotifers and even a crustacean. Fungi have also been found! All of this living biomass and all of this biological diversity is supported by the consumption of bacteria that, in turn, exist via the oxidation of a wide variety of inorganic atoms and molecules! This is an ecosystem that is far removed from the sun and photosynthesis. In fact, if the sun were extinguished and the Earth somehow survived, these tiny invertebrates and their trophic base of bacteria would continue to exist as long as the Earth’s heat (derived from the radioactive decay of unstable elements) persisted.
Amphibian Halloween Costumes
Hellbender salamander. Photo by B.Gratwicke. Wikimedia Commons.
Amphibians are the oldest group of terrestrial vertebrates. They arose during the Devonian Period of the Paleozoic Era some 370 to 400 million years ago and are the evolutionary forerunners of all of the terrestrial vertebrate groups. Most amphibians lay their eggs in water and have early life stages (larvae) that develop as aquatic organisms (tadpoles of frogs are an excellent example of this). I have written a number of blogs about amphibians: I have talked about the wood frogs down at Ohiopyle ( see Signs of Spring 4, March 22, 2018), the amphibians in my yard ( Signs of Fall 5, October 6, 2016), and the hunt for salamanders at Harrison Hills Park (Signs of Summer 4, June 18, 2015).
I have also written about the massive, on-going extinction of amphibian species along with a few hopeful points about their persistence or recovery or reappearances (like the genetic insights recently made about the Chinese giant salamanders and the adaptations of Panamanian frogs to the deadly chytrid fungus, or the rare hellbender salamander caught in the nearby Kiskiminetas River two summers ago (Signs of Summer 7, July 19, 2018).
Something that we didn’t know about amphibians, though, was that they decorate themselves with eerie, mostly green, biofluorescent markings as if they were going out trick-or-treating for Halloween.
Eastern tiger salamander. Photo by J. Lamb and M. Davis
In a paper published in Scientific Reports (February 27, 2020) two scientists from St. Cloud State University in Minnesota examined amphibians from eight salamander families, five frog families and one family of caecilians (limbless amphibians) at the Shedd Aquarium in Chicago. They exposed these living (or, in some cases, freshly dead) amphibians to blue light and found that all of them displayed green to yellow patterns of biofluorescence!
Blue light has the shortest wavelength (450 to 490 nm) in the color arrays of the visible light spectrum and, therefore, the greatest amount of energy. Blue light also behaves differently than the other visible light components of the spectrum: for example, the other light waves pass relatively directly through the atmosphere on their way to the Earth’s surface while blue light waves scatter and disperse when they strike water molecules or the other gaseous components of the atmosphere. This causes the sky to look blue!
Blue light’s potent energy content contributes to macular degeneration and also digital eye strain. It also alters triggers specific retinal input into the brain that stimulates brain activity and suppresses the production of the sleep inducing hormone, melatonin.
The proportion of blue light in an ecosystem’s ambient light spectrum increases in deeply forested, shady habitats. It also increases at twilight. Amphibians, then, who predominately live in shady habitats and display predominantly crepuscular to nocturnal activity, are exposed to significant levels of blue light. The wide range of blue light biofluorescence observed from the amphibian species in this study suggests that this tendency of biofluorescence is a feature that developed far back in the evolution of modern amphibians!
The researchers do not know why amphibians glow under blue light. They speculate that it might function in “communication, sexual selection, camouflage, or improved visual acuity … or, perhaps (it has) no function at all in some lineages.”
Whatever the function is (or is not) these amphibians are well costumed for trick-or-treating!
Bats and Cactus Flowers
Espostoa cactus. Photo by M. Weigen. Freie Univ Berlin
Flowering plants have been co-evolving with pollinating animals for 120 million years. The remarkable diversities of flower shapes and colors are profoundly important to the flowering plants as they enable the plant to attract pollinators (often immensely specific pollinating species) and direct them to the pollen bearing organs (often via a nectar reward). Very simple flowering plants release great clouds of pollen into the air relying on the infinitesimal chance that some of the sperm bearing granules will fall on an appropriate type of flower. When plants connect with pollinators, though, the odds of successful pollen transfer go up considerably.
Many plants are pollinated by bats, and bats do not “see” plants or flowers in quite the same way as most other animals. Bats produce ultrasonic pulses that bounce off of objects in their environment. For a flower to be noticed by a bat, then, it must strongly reflect these ultrasonic waves.
A cactus in the Ecuadorian Andes (called Espostoa frutescens), though, has evolved a slightly different method of directing a searching bat to its flowers.
The flowers of this cactus are surrounded by dense systems of wooly hairs (called cephalia) which are designed to protect the flower and keep it from drying out in the cactus’ arid environment. The bat that has co-evolved to pollinate these cactus flowers (“Geoffroy’s tailless bat”) produces ultrasonic pulses in the range of 90 kHz. Instead of having flowers that reflect these ultrasound waves (thus “lighting up” the flower for the bat) the cehalia hairs surrounding the flower have evolved to be extremely absorptive of the ultrasound wave in the 90 kHz. The flower then shows up as an obvious, “lighted” spot in the middle of a dark “bullseye!”
The Grandmother Hypothesis
In many species females have longer life spans than males. Often, these life span differences can be explained by a higher male mortality due to injuries that arise from fighting between males as they compete for females with whom they may mate or from a greater exposure of males to predators when they are protecting their mates, offspring or flock or herd. Another way to explain these extended female life spans, though, is encapsulated in the “Grandmother hypothesis.” In human beings or in other species with extended nurturing periods of the young, longer female life spans could be evolutionarily selected for in situations where the post-reproductive females (the “grandmothers”) contribute in some positive way to the survival of their offspring or their offspring’s offspring.
I have talked about this “grandmother hypothesis” in terms of human beings before (Signs of Summer, August 22, 2019). There was, though, an article published in Science (December 9, 2019) that discussed the importance of “grandmother” killer whales.
Orca female and calf. Photo by C. Michel. Wikimedia Commons
Killer whales (more appropriately called “orcas”) live in family based pods. Male orcas in the wild live on average for 60 to 70 years while females in the wild live on average 80 to sometimes over 100 years. In captivity these life spans are greatly shortened (average life span of a captive orca is only 14 years!). Male orcas continue to be reproductively viable all trough their life span, while female orcas go through menopause somewhere around age 40 to 45. Females, then, live with their pods as non-reproducing individuals for 50 to 60 years, and it turns out that these “grandmother” orcas are extremely important to the survival of their offspring’s offspring!
Calves without a grandmother have a four-fold greater chance of dying in the next two year period of time than calves that have a grandmother. Much of this benefit is because of food sharing, and it is especially important during times of prey (like Chinook salmon) shortages. Mother orcas tend to freely share food with their male offspring, while grandmothers freely share food with both male and female “grandchild-whales.” Whales as old as 20 years of age have been shown to have increased rates of survival when they have a living grandmother orca.
My grandmother used to make me brown sugar sandwiches on home-made bread warm and fresh out of the oven. I bet she would have given me some of her salmon, too! Thanks, Grandma!