Image Credit: Davian Ho, Maya Peters Kostman, and Philippa Steinberg for the Innovative Genomics Institute, CC BY-NC-SA 4.0, Image Cropped
Tag Archives: featured
The time has come for the Stats Corner to wrap up as Ecology for the Masses closes. I want to thank Sam Perrin for bringing me on board, carving out a place for statistics on the site, and supporting my writing for the past two years. He was always generous with his time helping me brainstorm topics when I was out of ideas and providing helpful feedback to make the posts more engaging and accessible. We all have Sam to thank for the fun pictures that kick off each post as well. 🙂Read more
A couple of months ago, on a drive into town, my mum and I were listening to the radio. A particular segment, on adders in the UK, caught my attention. The guest, one Nicholas Milton, author of “The Secret Life of the Adder: The Vanishing Viper”, spoke passionately and informatively about the plight of the adder in Britain. He specifically noted how negative public perception of the UK’s only native venomous snake, egged on by media sensationalism and fearmongering, played into the difficulties in protecting and campaigning for the adder.Read more
When you think about contagious diseases, the image that’s conjured is probably not a romantic one. Spanish flu, polio, the Black Death – while they’ve all shaped our history, they’re not exactly prime fodder for light-hearted musicals or sitcoms. And while many of these diseases we’ve successfully conquered as a society, we still see many diseases that do not have a cure yet.Read more
Image credit: Movie poster advertisement for Tarantula (1955), Public Domain, Image Cropped
In the mid twentieth century, movies like ‘Tarantula’ and ‘Them!’ set the scene for what life would be like if giant bugs existed. Scenes filled with nightmares arisen from experiments gone wrong, children-stealing ants, great taglines like “Science’s Deadliest Accident”, and some unbelievably outdated special effects.
Luckily, giant bugs don’t exist… Anymore.Read more
Climate anomalies and competition reduce establishment success during island colonization (2022) Nicholson et al., Ecology and Evolution, https://doi.org/10.1002/ece3.9402
The colonisation of islands by species on the move has given rise to some of the most fascinating ecosystems around the world. Think the marsupials of Australia, Papua New Guinea’s Birds of paradise, or the multitudes of weird and wonderful creatures that pop up in tiny unexpected landmasses around the globe. On the flipside, invasive species arriving on islands can hit like veritable hurricanes, with similar (though admittedly slightly slower-moving) effects. Yet for these phenomena to take place, a species first has to make it to an island from the mainland. This isn’t always super easy, seeing as islands may be tiny and hard to find, or way out in the middle of nowhere.
But even if they do arrive, whether or not a species is able to persist depends a lot on circumstance. If a large storm or drought hits (increasingly likely with climate change upping the frequency of extreme weather events) just after a species arrives on an island, it might wipe them out before they’ve even gotten started. A competitor already having set up shop there could decrease a species’ survival chances too. Today’s authors were lucky enough to have introduced a new species to a series of islands with and without competitors, all of which were hit by a drought just after one of the introductions. Let’s see how the populations fared.Read more
Nature is complicated and the environment is vast. How can we possibly learn all there is to know about our surroundings? Aspects of our natural world like life population dynamics and life histories influence the very survival of species, but understanding these requires data from long time periods. Luckily, technology and the remarkable commitment of some scientists have meant that we are making progress in data collection by establishing many long-term monitoring networks that collect a variety of information at many different locations. Weather sensors keep track of temperature, precipitation, and wind speed. Air and water-quality sensors keep track of what is in the air we breathe and the water we drink.Read more
How do we motivate people to protect ecosystems?
At this stage in the climate crisis, many of us are very aware that ecosystem destruction and biodiversity loss are huge problems, bringing about everything from rapidly expanding deserts to global pandemics. We are acutely conscious that something incredibly valuable is being destroyed, and we want to protect it.
However, there are also people who aren’t very aware of the scale of ecosystem destruction, and therefore don’t seem to be doing anything about it. Motivating these people to protect ecosystems – or at least stop destroying them – is a huge problem. A problem so big, some people have even tried to throw money at it.Read more
Would you rather stab, or be on the receiving end of a stab? This may seem like a confronting question, but it’s the dilemma many flatworms face when a mating opportunity arises.
Option 1: You are a flatworm and have just been stabbed by a stubby penis. You now have puncture wounds that must heal, after which you must carry fertilized eggs which you need to lay and protect upwards of 24 hours. Oh, the energy demands!
Option 2: Flatworm victory! You have successfully stabbed your opponent with your stubby penis before they could stab you. Your sperm has now fertilized their eggs. With this win, you move on with life and wait for your next mating “opponent”.
Which option do you choose? If you still can’t choose, it’s a good thing you aren’t a simultaneous-hermaphroditic flatworm. These flatworms have both fully functional male and female reproductive capabilities that can be used interchangeably, unlike other hermaphroditic species who switch back and forth during different phases of life. One might say these individuals have the capability to “choose” what role they want to play, male or female. Although, those forced into the role of reproductive female may disagree…
It is believed that individuals fight to “remain male” (i.e., not be fertilized) because sperm is biologically cheaper to produce than eggs, and males can produce more offspring than females over a lifetime. This type of fight has been thought to be “pure evolutionary selfishness”.
It was only discovered recently, after Dr. Leslie Newman and Dr. Nicholas Michiels spent 20 hours continuously watching pairs of captured flatworms. They observed that when an individual encounters another, both assume a fighting stance, curling their bodies back to display their penises. Next, they began to fight, each attempting to stab the other, which could last from 20 to 60 minutes.
Different species fight with different strategies. For example, racing-line flatworms (Pseudocerotidae bifurcus) use their penis to repeatedly strike at one another until one succeeds, injecting sperm under the skin of the other. Once the sperm is injected, it moves through the body to find and fertilize the eggs. Persian carpet flatworms (P. bedfordi, pictured above) instead use their penis like a water gun, ejaculating anywhere on their opponent’s body. With a sperm cocktail that dissolves flesh, it burns its way through various tissues until it reaches and fertilizes the eggs.
Penis fencing is the term scientists use to describe this behavior to “remain male”. This mating behavior isn’t seen amongst all flatworm species, only certain species within the family Pseudocerotidae. In the 1990’s there were only two species of flatworm known for this behavior, however as of 2020, the number has grown to 16.
Evolution of Penis Fencing
Species of flatworms can use sexual reproduction (need both gametes; sperm and egg), asexual reproduction (does not require both gametes, obtain all DNA from parent), or both. Those that use both, do so depending on which strategy is favoured by the environmental conditions. For example, sexual reproduction is favored under harsher, more unpredictable conditions, since genetically variable offspring are often better able to adapt and survive these conditions. Asexual reproduction may be favored when individuals are scarce, however it tends to be avoided as there is on average a 50% loss of genetic diversity per generation, subsequently increasing the probability of inbreeding in future generations. If asexual reproduction does occur, it can occur through budding or transverse fission. Budding occurs when ‘buds’ (i.e., outgrowth) grow out of the flatworm’s body until they are large enough to break off as new individuals. Fission, on the other hand, involves an individual being cut in half, with each half becoming a new individual.
A species may employ different hermaphroditic strategies of cross-fertilization depending on their ecological niche. These include delivery of sperm to a sperm-receiving organ of the mating partner, or hypodermic insemination of sperm into the cellular tissue by a modified penis that enables individuals to pierce the body wall of their partner. It is believed that the willingness to invest as little resources as possible into their offspring is very strong in hermaphroditic species, leading to these extreme mating behaviors such as penis fencing.
Yet penis fencing does not always occur when individuals meet. Four possible scenarios have been observed when individuals encountered one another:
- Both partners were receptive to mating and penis fencing was observed,
- Both partners were receptive but no penis fencing was observed,
- Only one partner was receptive and no penis fencing was observed however insemination was successful, and
- Neither were receptive to mating.
If penis fencing occurs, it typically leads to successful sperm insemination for one or both individuals. Number 3 may be the result of other mating behaviors. For example, mating Starry flatworms (P. stellae) will curl around each other, swimming in circular motions in attempts to inseminate each other.
Outcomes of Penis Fencing
A more recent study in 2020 found that penis fencing results in three outcomes; 1) both individuals were inseminated, 2) one individual was inseminated, or 3) neither were inseminated. These researchers found penis fencing to be more of a duel or contest mating ritual, rather than an aggressive, violent behavior as was originally thought. This is because they found different scenarios where penis fencing occurred that resulted in neither individual being inseminated, or where no penis fencing occurred resulting in at least one individual being inseminated. Although we may think of penis fencing a little differently now, one thing that will forever remain constant are the words of David Attenborough, “its only solace is knowing it’s young will carry the genes of a master swordsman”.
Jennifer Merems is a writer and researcher focusing on behavioral and nutritional ecology. She is currently a PhD candidate in the Department of Forest and Wildlife Ecology with the University of Wisconsin-Madison. You can learn more about Jennifer by following her on Twitter at @atyourcervid.