Adapting to Change: Phenotypic Plasticity in Locusts, Humans and Other Animals

in StemSocial3 months ago (edited)

Locusts are mentioned in the Bible (Judeo-Christian) as one of the Ten Plagues of Egypt. This ancient scourge exists today on every continent, except Antarctica. However, locusts do not swarm with devastating ferocity on every continent. This agricultural threat affects the livelihood of at least 1/10 of the world's population. One swarm in East Africa this year consumed, in a single day, food that could have fed 35,000 people.

Locust Swarm, Western Sahara (1944)
Locust swarm western sahara 1944 Eugenio Morales Agacino's Photographic Archive 3.0 share alike.jpg
Image credit: Author, Universidad Autónoma de Madrid Eugenio. Source, Morales Agacino's Photographic Archive. Via Eugenio Morales Agacino's Virtual Exhibition. Used under a CC share-alike 3.0 license Spain.

In order to mitigate the damage of swarms, scientists are focusing on the evolution of locust behavior. What causes an anti-social, non-aggressive insect to morph into an aggressive, group-oriented menace? Not only is there a dramatic behavioral change in the insect, but the change comes about suddenly and also manifests in physical appearance.

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Desert Locust, Gregarious (Social) Phase
desser locust gregarious phase DataBase Center for Life Science DBCLS 4.0.jpg
Image credit: DataBase Center for Life Science (DBCLS). CC4.0 license.

Desert Locust, Solitary (Anti-Social) Phase
desser locust  soliltary phase DataBase Center for Life Science DBCLS 4.0.jpg
Image credit: DataBase Center for Life Science (DBCLS). CC4.0 license.

Desert locusts (Schistocerca gregaria) are among the most damaging in the world. Approximately 20% of the world's population, mostly in Africa and the Middle East, is affected by this locust species

Phenotypic Plasticity

The ability of an organism to change in response to environment is called phenotypic plasticity. This is considered an adaptive strategy. Responding to the environment is designed to increase the survival of the species. However, nature is rarely predictable . When the change is made in the insect’s juvenile stage of development, success of the strategy is dependent upon the stability of the environment. If the adaptation is irreversible, and the environment changes, survival may be endangered rather than enhanced.

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Snake Skeleton

Snake skeleton dbking 2.0.jpg
Image credit: dbking. Used under a CC 2.0 license

One animal that demonstrates at least one aspect of fixed phenotypic plasticity is the snake. The number of vertebrae an adult snake has is partly dependent upon the environment (mostly temperature) to which the snake was exposed as an embryo. Though a snake grows throughout its life, growth potential and therefor body size, is influenced by the number of vertebrae. Ultimately, the body size of a snake affects its food foraging success, since snakes swallow their prey whole. And, obviously the efficiency with which an animal forages for food affects its survivability. In this way, the phenotypic plasticity of an embryonic snake may affect the suvivability of the adult.
(Information on snake growth derived from Nature: Rethinking phenotypic plasticity and its consequences for individuals, populations and species)

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While it is temperature that influences the number of vertebrae a snake may grow, in locusts the environmental trigger is population density. In locusts, there is a complex interaction between smell, touch and the insect's central nervous system. The proximity of other locusts sets off this interaction.

Once triggered, the central nervous system signals that massive doses of serotonin be released. Within hours of the seratonin infusion, solitary locusts become gregarious and join a swarm.

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A Locust Depositing Eggs in Soil

locust ovipositing_eggs_into_the_soil credit Retro Lenses 4.0.jpg
Image credit: Retro Lenses. Used under a CC 4.0 license

Sensory receptors on the hind legs of the locust are key to the seratonin release. When these receptors are stimulated by contact with another locust, the message is sent to the nervous system and the process of transformation to the gregarious state begins.

All Locusts Are Grasshopper; Not All Grasshoppers Are Locusts

Spotted Bird Grasshopper (Schistocerca lineata)
Schistocerca lineata  xpda 4.0.jpg
Image credit: xpda, Reference: Bugguide.net, Schistocerca lineata. Used under CC 4.0 license

Through a series of rearing experiments, Dr. Hojun Song, an entomologist at Texas A & M University, determined that some grasshopper species do not respond to population density by swarming. Some respond only by changing appearance. There is no behavioral effect. Some grasshopper species do not respond to crowding in either way: they neither change appearance nor behavior.

According to Dr. Song, the grasshopper species featured in the picture above, Schistocerca lineata, changes color when crowded but does not change behavior.

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A Hopper Band (Locust Nymphs) in a Gregarious Phase
locust gregaria_dense_hopper_band credit ChriKo 4.0.jpg
Image credit: ChriKo. CC license 4.0

Upon hatching from an egg, a locust emerges as a wingless nymph, a hopper. It can be gregarious or solitary. In the picture above, hoppers are swarming on the ground. Researchers in China are experimenting on nymphs to see if they can turn off the trigger that makes the insect gregarious. The research focuses on a hormone, JH (juvenile hormone) secreted by the hoppers. So far, the scientists have been able to make the nymphs more or less repulsive to each other by manipulating this juvenile hormone.

Cannibalism

Locusts are cannibals. This, it is believed, is why sedentary locusts stay away from each other. They don't want to be eaten. According to an article published by the University of Sydney, locusts in crowded circumstances, ..."become sociable and move away from locusts who approach them in order to avoid being eaten. But at the same time they are attracted to locusts moving away from them because of their general tendency to follow others".

Desert Locust Head
Desert Locust_head Adam Matan 3.0.jpg
*Image credit: Adam Matan. Used under a CC 3.0 license

Another article, published in the World Economic Forum, explains that a locust is more likely to be eaten if another locust approaches head first. Hence, locusts align side by side in a swarm. "...any locust that is out of line with its neighbours will expose its vulnerable flank and face a greater chance of being cannibalised. By being in line, they will be safer – but will also help hold the swarm together."

Part of a Settled Swarm in Sudan, 2007
Schistocerca gregaria part of a settled swarm sudan ChriKo 4.0.jpg
Image credit: ChriKo. Used under a CC 4.0 license

Phenotypic Plasticity in Humans

Most of us are familiar with a common form of human phenotypic plasticity: exercising for physical conditioning. We are also familiar with the intransigence of cancer cells. These cells, in humans and other animals, demonstrate phenotypic plasticity. An article in Science Direct explains how tumor cells adapt, "by migrating away from the primary site (Biddle et al., 2011), where they may utilise plasticity...to travel to and colonise distant tissues".

Another example of human phenotypic plasticity, was demonstrated in a rather novel experiment (Strategic Ejaculation in Reponse to Sperm-Competition Cues). This experiment showed that men who view women having multiple partners show an increase in sperm production.

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Conclusion

Locusts are fascinating creatures, not only because of their economic and social importance, but also because they are ideal examples of phenotypic plasticity. The ability to adapt is essential to survival: "Plasticity is a universal property of living things". Whether it be a snake, a locust or a ghost crab, understanding these animals is a path to understanding life, and ourselves.

I hope readers found this article interesting and relevant to their lives.

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Some Sources Used in Writing This Blog
  1. The Biomedical Scientist: https://thebiomedicalscientist.net/science/ten-plagues-egypt
  2. VOX: Locust Plague Swarm Outbread Africa Asia: https://www.vox.com/2020/5/20/21158283/locust-plague-swarm-outbreak-africa-asia-2020
  3. Research Features: https://researchfeatures.com/locust-swarms-powerful-force-nature/
  4. World Economic Forum: https://www.weforum.org/agenda/2020/06/locusts-africa-hunger-famine-covid-19/
  5. Frontiers in Science: https://www.frontiersin.org/articles/10.3389/fevo.2020.517183/full
  6. Nature: https://www.nature.com/articles/hdy201492
  7. Plos One Journals: https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1008762
  8. Phys.org: https://phys.org/news/2012-08-solo-sociablehow-locusts-cannibalism.html
  9. Journal of Experimental Biology: https://jeb.biologists.org/content/209/12/2344
  10. Science Direct: https://www.sciencedirect.com/science/article/pii/S0012160617301756#s0045
  11. Science Direct: https://www.sciencedirect.com/topics/psychology/phenotypic-plasticity
  12. NCBI: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7198268/
  13. Frontiers in Science: https://www.frontiersin.org/articles/10.3389/fevo.2016.00051/full
  14. Oxford Academic: https://academic.oup.com/icb/article/57/2/171/3966723
  15. Pub Med: https://pubmed.ncbi.nlm.nih.gov/16731808/
  16. NCBI: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4815455
  17. Physiological Reviews: https://journals.physiology.org/doi/full/10.1152/physrev.00029.2013
  18. JStor:https://www.jstor.org/stable/49916?seq=1

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Locust accent GIf derived from Pixabay, by Prawny
Snake Gif derived from image on Paint3D

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Great article and thank you for sharing. I never though of myself as adapting to the environment but that makes a lot of sense.

Thank you! That was one of my favorite things in the research, learning how the concept of adaptability applies to all of us, all living things. The thought is kind of humbling and ennobling at the same time.
Thank you for stopping by.

Thanks for your contribution to the STEMsocial community. Feel free to join us on discord to get to know the rest of us!

Please consider supporting our funding proposal, approving our witness (@stem.witness) or delegating to the @stemsocial account (for some ROI).

Thanks for including @stemsocial as a beneficiary, which gives you stronger support. Using the STEMsocial app could yield even more supporti next time. 
 

Thank you for supporting my blog and endorsing my post. I do delegate, from @agmoore2 and @agmoore. I tried posting on @stemsocial app but the post wouldn't load. Also, @lemouth is my proxy, so that covers me on the witness front :)) Also, I have supported a funding proposal. Perhaps this is a new one? I'll check.
I value @stemsocial very much. There's nothing else like it on the blockchain.

You're getting posting errors on the app too?

I still need to update the app for HF24. The HF happened at a time the COVID business took over all my time. Currently, I have basically no time to do anything except university and resaearch work, and this is the case for almost 9 months. I could explain in all glory details what my life has become on a blog... but I don't even have the time to do so... I hope things will get better in a couple of months...

PS: I am back on discord at least, as I will use discord for teaching ;)

My apologies if it appears I was casting aspersions. It wasn't my intent in any way. I just thought that I was the only one with the issue. I kept seeing postings coming in through the app, and I was curious about whether or not I was doing something wrong.

I had the fortune, or perhaps misfortune, of seeing my computer crash beyond repair before my eyes, and I opted for the less expensive PC desktop as opposed to Apple. Yet, I encountered the same issue. I am sorry you're going through what you're going through—my best wishes for improvements soon.

Thanks for your understanding. And don't worry, I didn't take it as an offense at all ;)

It just won't load. Comments also.

I know.... See my reply to scholaris' comment :(

Hi @lemouth,
The virus takes center stage. Things will be put to right when this is over. Just survive :)

Surviving is fine for now. The rest is just so exhausting :)

Thanks for the nice words! I hope you are safe!

Your post has been voted as a part of Encouragement program. Keep up the good work!
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Thank you very much for your support. I'm not familiar with your mission, but it seems worthy so I will check it out.
Thanks again for the endorsement.

Great post as always. Those locusts are a farmer's nightmare.

Thank you very much @pokerm. I worked hard on this and it feels good to have that appreciated.

I've ever really read anything relating to locust until now and what an interesting piece to start with. Now I understand why they form a swarm. So, they only feed on their fellow locust as their own form of cannibalism or what? Then, how vulnerable do you think every locust within a swarm would be when they are busy feeding on crops?

Hi @gentleshaid,
Thanks for reading my blog and for finding it interesting. They will eat anything, and even seem to prefer eating each other. Here's a YouTube video that explains what drives them and how they behave.

I didn't know any of this but found it fascinating as I read.
Peace and health,
AG