Giant Invertebrates: Scientists Deadliest Accidents or Competitive Superiority Through Evolution?
Image credit: Movie poster advertisement for Tarantula (1955), Public Domain, Image Cropped
Tag Archives: evolution
Cockatoo Can Play At That Game
Australia is once again at war with the birds – but instead of trying to fight off emus in the outback, this time it’s a bit closer to home(s). The cockatoos of Sydney have taken the saying ‘one man’s trash is another man’s treasure’ to heart, and have taken to ‘dumpster diving’ in search of food. Although the challenge of keeping urban wildlife out of rubbish bins is not a uniquely ‘Australia problem’, finding a solution to thwart the brainy cockatoos is proving difficult. For every deterrent that humans come up with, the cockatoos seem to find a work-around – similar to the evolutionary arms race that we might expect between a predator and prey.
Read more: Is bin-opening in cockatoos leading to an innovation arms race with humans?
What makes this really cool is that it is essentially an ‘evolution in action’ scenario happening right in the backyards of Sydney residents! There are different strategies being deployed by both the humans (to deter the the cockatoos) and the cockatoos (to open the rubbish bins). These strategies have costs for both parties as well (how long it takes to secure the rubbish bin vs how long it takes to open) and we expect these strategies to experience different selection pressures that might lead to the selection of an optimal rubbish bin securing strategy (that is until the cockatoos work out how to thwart the humans once again).
I for one am rooting for the birds – if at minimum so that they can claim having defeated humans not once but twice!
Tanya Strydom is a PhD candidate at the Université de Montréal, mostly focusing on how we can use machine learning and artificial intelligence in ecology. Current research interests include (but are not limited to) predicting ecological networks, the role species traits and scale in ecological networks, general computer (and maths) geekiness, and a (seemingly) ever growing list of side projects. Tweets (sometimes related to actual science) can be found @TanyaS_08.
To Stab, Or Not To Be Stabbed: The Sex Lives of Flatworms
Image Credit: Hectonichus, CC BY-SA 3.0, Image Cropped
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.
Dreamweaving
We’ve probably all had at least one dream about embarrassing ourselves at school in some way… which begs the bigger question – do other animals also dream about embarrassing situations?? Note here I said animals, as new research by Dr. Daniela Rößler’s team at the University of Konstanz suggests that not only the usual suspects such as dogs and cats, but other more surprising animals such as octopuses and worms dream as well! It turns out even spiders need that all too precious REM sleep.
Read more: Regularly occurring bouts of retinal movements suggest an REM sleep–like state in jumping spiders
One really cool thing from this study – most animal eyes don’t move like ours so it makes it challenging to actually pick up these sleep cycles. BUT because baby jumping spiders are translucent and have the neat feature of having movable retinal tubes, researchers can actually detect the rapid eye movement associated with REM sleep. This has really cool implications for understanding the evolutionary history behind sleep as well help us to better understand the physiological function of REM sleep.
Tanya Strydom is a PhD candidate at the Université de Montréal, mostly focusing on how we can use machine learning and artificial intelligence in ecology. Current research interests include (but are not limited to) predicting ecological networks, the role species traits and scale in ecological networks, general computer (and maths) geekiness, and a (seemingly) ever growing list of side projects. Tweets (sometimes related to actual science) can be found @TanyaS_08.
Triffids Underground
Carnivorous plants are (to put it bluntly) pretty darn dope. I mean what’s cooler than the idea that ‘boring’ and ‘unremarkable’ plants have upgraded themselves from prey to predator!?! These carnivorous beasties have served as inspiration for an array of scary monsters in the world of fiction, such as the Triffids, Audrey II and more recently the Demogorgon from Stranger Things (I really want to add Bulbasaur and his evolutionary lineage to the list but I don’t think that’s more a symbiotic relationship).
But it turns out that we could’ve made these creatures even more terrifying, but still biologically plausible, by making them capable of haunting not only those living above ground but those below ground too…
A new species of carnivorous plants from Borneo (described only this year) have been found to have underground (yes you read that correctly) pitchers, the acid-filled tubs into which unsuspecting insects often fall. Not only is this really neat but it also shows we have so much left to discover and learn about the natural world…
But also just imagine carnivorous plant inspired monsters with the ability to move swiftly underground like the sandworms from Dune…
Tanya Strydom is a PhD candidate at the Université de Montréal, mostly focusing on how we can use machine learning and artificial intelligence in ecology. Current research interests include (but are not limited to) predicting ecological networks, the role species traits and scale in ecological networks, general computer (and maths) geekiness, and a (seemingly) ever growing list of side projects. Tweets (sometimes related to actual science) can be found @TanyaS_08.
Can Fishes Adapt To Our Warming Oceans?
Low potential for evolutionary rescue from climate change in a tropical fish (2020) Morgan et al., PNAS, https://doi.org/10.1073/pnas.2011419117
The Crux
As the planet warms thanks to climate change, the massive bodies of water that are our oceans grow hotter. Since they’re larger, and much poorer conductors of heat, they don’t tend to vary in temperature as much as the land does, which means many species will have to get used to longer, warmer periods.
If species can adapt to hotter temperatures through thermal acclimation, ecosystems may not be too harshly affected. However if they’re unable to adapt, marine ecosystems may undergo rapid changes as they lose native species. Today’s researchers looked at a key study species – the zebrafish – in order to figure out how well fish can respond to increasing temperatures.
Read moreBuzz Show
To start this interview is 100% the Zootopia version of the Graham Norton show – featuring Bunnydict Cumberbatch because why not (we’re pretty sure that’s his real name anyway). On the docket for tonight’s interviews – Graham the Gerbil/Hamster looks into the history of the human-biting ‘London Underground mosquitoes’ – more specifically how they probably did not evolve in London. Check out the lead author’s thread below for a more in-depth take!
Tanya Strydom is a PhD candidate at the Université de Montréal, mostly focusing on how we can use machine learning and artificial intelligence in ecology. Current research interests include (but are not limited to) predicting ecological networks, the role species traits and scale in ecological networks, general computer (and maths) geekiness, and a (seemingly) ever growing list of side projects. Tweets (sometimes related to actual science) can be found @TanyaS_08.
Getting Hot Hot Hot
How melanism affects the sensitivity of lizards to climate change (2022) Mader et al. , Functional Ecology, https://doi.org/10.1111/1365-2435.13993
Image credit: Tony Rebelo, CC BY-SA 4.0, via Wikimedia Commons
The Crux
Climate change is a fact of life. Every day we uncover more of the negative effects it will have on the various animals, plants, and fungi in the natural world. Species range contractions are one such effect, and they occur when the area that a given species normally occupies shrinks. They are directly linked to a species’ risk of extinction, with this risk growing as a species inability to adapt to new environments grows. Though the theory sounds logical, many of the exact mechanisms behind range contractions are still unknown.
Ectotherms are organisms that depend on the surrounding environment to regulate their own body temperature, making them particularly vulnerable to climate change. Many different biological mechanisms are involved in regulating temperature, but the ability to reflect solar radiation is a key player. Indeed, the ability of organisms to reflect solar radiation (aka energy from sunlight) is part of the thermal melanism hypothesis (see Did You Know?). Melanistic (darker) organisms may be favored under climate change, due to the protection against UV radiation provided by melanin. However, melanistic individuals are more prone to increased heating, which can be bad. Today’s authors sought to understand how climate change would affect melanistic organisms.
Read moreWhy Are There So Many Species?
The causes and ecological context of rapid morphological evolution in birds (2022) Crouch & Tobias, Ecology Letters, https://doi.org/10.1111/ele.13962
Image credit: Andrej Chudý , CC BY-NC-SA 2.0
The Crux
One of the biggest questions facing evolutionary ecologists is why some groups of organisms contain SO MANY species, while others are relatively sparse in comparison. We’ve discussed adaptive radiations on Ecology for the Masses before, which is when a burst of speciation occurs within a group, with new species adapting to fill new ecological niches. It could be that the reason for such uneven groups is that some clades, or related groups of organisms, are more prone to such adaptive radiations than others. If this is true, it would mean that such clades experience not only an increase in the number of lineages (species) that they contain, but also the number of traits they exhibit.
Increases in the speciation rate and trait evolution are the hallmarks of adaptive radiations, but they may not occur at the same time, which can lead to some different outcomes. Clades may diversify rapidly, without really evolving new traits, and this is known as a “non-adaptive radiation“. In contrast, a lineage may quickly evolve new traits without speciating, which is known as an “adaptive non-radiation“. To understand the causes and context of such evolutionary scenarios, today’s authors studied the history of bird evolution.
Read moreBigger is Better
Population size impacts host-pathogen coevolution (2021) Papkou et al. 2021, Proc B, https://doi.org/10.1098/rspb.2021.2269
Image credit: Kbradnam, CC BY-SA 2.5, via Wikimedia Commons
The Crux
Host-pathogen interactions are maybe best characterized as a battle – a pathogen (a parasite that causes disease) doing what it can to maximize how much it can get from a given host organism, and a host doing what it can to defend itself from this endless attack. As a result, hosts and pathogens are locked in an endless evolutionary battle, whereby hosts evolve to better defend themselves and pathogens evolve to better attack the host. A key factor in this battle is population size, as this affects the evolutionary potential of a given population of organisms to respond to selection.
The larger a population of hosts, the more novel genetic variants there are, which are simply organisms with different genetic make-ups, which can be the result of mutations popping up or through combinations with other genetic variants within the population. The more variation there is, the more diverse the population is, and the more chance it has of carrying the genes that could help it respond to a new threat, like a pathogen.
This means that a larger host population is more likely to have a genetic variant that is able to defend itself from these pathogens. That variant will then be selected for and the host population will become more resistant to that pathogen over time. While a lot of theory has been dedicated to understanding these coevolutionary battles, actual experimental evidence is lacking. Today’s authors used a model system to conduct evolutionary experiments to test the effect of host population size on host-pathogen coevolution.
Read more
Ecology for the Masses 
