by Cheyenne Tait – I think that parasites must hold some kind of deep fascination for biologists. Either that or I just attract strange colleagues. I don’t know what else can explain how often I’ve been drawn into conversations, usually with people I’ve just met at workshops or conferences, about the most gruesome parasites we can collectively think of.
For instance, how about those grasshoppers that throw themselves into bodies of water, committing suicide, only to spool out a fine, wriggling worm (horsehair worm) which happily swims off to infest more grasshoppers? There are truly awful videos of this on Youtube, I don’t suggest you go see them if you’re squeamish.
And of course these conversations usually happen at lunch. It must be some kind of unwritten rite of passage for a biologist – can you hold in your lunch while you talk merrily about what else might be inside you… also eating your lunch?
In fact, I recently read the book “Parasite Rex” by Carl Zimmer. If you want to be as freaked out, and fascinated, as I am by colleagues’ stories at lunch, and/or gather your own stories to tell, it’s a good book to read. Some of the more interesting examples of parasitism?
There’s the gruesome – Leishmania brasiliensis, a microorganism parasite that, if left untreated too long, is said to render its victims faceless. Similarly gruesome are the multitude of human parasites mentioned in Carl Zimmer’s book. Guinea worm, exploding from a cyst in a person’s leg, is a particularly nasty image. But luckily Guinea worm is almost eradicated.
The parasite behind malaria, plasmodium, however, is another story entirely in that it is not on the wane, and it’s deadly. Its effects on mankind have been powerful, with evolutionary consequences (sickle-cell disease in Africa, for instance). But in terms of gruesome, I’d say that the mosquito has it worse. Plasmodium expertly manipulates the mosquito’s behavior, first making it more likely to avoid humans (and avoid being killed) as the parasite is growing by having the mosquito not eat. Then, once in adulthood, plasmodium shifts and somehow makes the mosquito more ravenous, more likely to bite human hosts, so it can be passed on.
Actually, a lot has been studied on parasites that somehow possess “mind control” powers over their hosts. Flukes that make ants climb to the top of a blade of grass so that they can be eaten more easily by their parasite’s next host. Parasitic wasp pupae that somehow gain active protection from the half-eaten, half-alive caterpillar they emerged from, with the poor insect thrashing about in response to disturbances and only getting to die once the wasps emerge from their pupae. Toxoplasmosis influencing rats to be less afraid of cats. It’s all about chemicals, often inside the nervous system, and it’s all because the parasite involved needs to get to its next life stage. When it’s ready to go, the current host better watch out!
But the book “Parasite Rex” isn’t out to show us how disgusting and deadly parasites are, with mind control powers that make them perfect stars for movies like “Alien”. The book wants to show how far-reaching their effects can be. How powerful they really are – they’re the “Rex”, the king! It turns out that parasites not only manipulate single hosts, their presence impacts entire food webs. The book mentions deer that carry a parasite which devastates moose but is relatively benign inside the deer. Thereby, the parasite keeps the moose population down and allows the deer to co-exist with moose, which should be the stronger competitor for food and drive out the deer. Instead the parasite balances out their relationship.
Another example of the ecological involvement of parasites, tiny and unseen, centers on the killifish. One of its particular parasites affects its nervous system, making the fish more likely to be near the surface of the water, where birds, the parasite’s next host, are more likely to capture and eat it (Lafferty and Morris 1996). Parasitized fish are apparently 30 times more likely to be taken by birds than non-parasitized fish. This, of course, means the birds are parasitized on a massive scale, and only works out if the food resource (the fish) is worth more to the birds’ fitness than the negative impact of the parasite feeding off the bird. Thus parasites are involved in complex ecological interactions, manipulating the biological fitness “calculus” not just from the bottom up or the top down, but from every angle in between.
With such far reaching ecological effects, parasites which have an effect on evolution should not be surprising. In fact, parasites are prominent in the history my own study species, Rhagoletis pomonella. The apple maggot fly is infested by its unique group of Braconid wasps. In fact, they are one hypothesis for what drove the apple maggot fly to speciate, moving from its original host fruit (hawthorn, where it is parasitized at very high levels by wasps), to a new host fruit (apple, less parasitism): the enemy free space hypothesis (Feder 1995). Flies switched hosts to escape their enemy, the wasp. However, given time, the wasp of course followed the fly. Thus the fly’s speciation event, driven possibly in part by the wasps, led to a cascading speciation event (Hood et al. 2015), wherein the wasps followed the flies to the new host fruit and diverged from the other wasps, each on their own way to becoming distinct species.
Braconid wasps emerging from apple fly pupae
The interplay of ecology, evolution, and parasitism is a complicated dance that scientists are only just starting to get a hang of. Whether epiphanies occur over lunch or not, well, that depends on the strength of the individual scientist’s stomach.
Feder, Jeffrey L. “The effects of parasitoids on sympatric host races of Rhagoletis pomonella (Diptera: Tephritidae).” Ecology 76.3 (1995): 801-813.
Hood, Glen R., et al. “Sequential divergence and the multiplicative origin of community diversity.” Proceedings of the National Academy of Sciences 112.44 (2015): E5980-E5989.
Lafferty, Kevin D., and A. Kimo Morris. “Altered behavior of parasitized killifish increases susceptibility to predation by bird final hosts.” Ecology 77.5 (1996): 1390-1397.
Zimmer, Carl. Parasite rex: inside the bizarre world of nature’s most dangerous creatures. Simon and Schuster, 2000.
by Geetha GT – Bengaluru – “The Garden City” as it is called, is certainly missing its greenery essence. And in conjunction with a current population of 12.3 million, rising air pollution is suggested to be causing lung problems in students, as said by a survey.
Change is crucial, but at what cost? A transformation like what Bengaluru has gone through makes every person’s heart freeze as it changes from the garden city to a concrete town. To observe this journey back in time, see how landmarks in Bangalore well-known today appeared seventeen years back. These images also show how significantly sites have changed and how time has distorted the city and its public.
So, here is a travel back in time portraying a few places of Bengaluru’s changeover from The Green City to The Concrete Jungle.
by Shannon – Scientists don’t have “typical days”. Any particular day may find us performing research, advising, teaching, giving a presentation, writing a manuscript, working on grant applications, or endlessly dealing with administration. On Monday, June 5, 2017, I decided to document my day. It was a good day to document – not too stressful – but shows the type of things I think about in a typical 16 hour day.
6:30 AM: My daughter Grace comes in to tell me that she is hungry.
6:45 AM: First email check of the morning. Emails from US and Australia to respond to. Goal planning lists from students. Review request from a journal and more paperwork on a grant application. Here we go!
7:00 AM: My husband brings me my first transfusion of coffee for the day, which he makes every morning out of self preservation.
7:35 AM: Grace wants a “high ponytail” as she does every morning. I frantically put it up so she doesn’t miss school, realizing that I forgot to comb my own hair. Hurry.
8:00 AM: Ride to work on the little golf cart that transports between the faculty housing and campus. Quickly surf the News on the way – Fox News, BBC, NPR, Times of India. What is going on with the US?
8:15 AM: Arrive at work. Sit down to respond to emails. First meeting starts at 9:00. Need to print out permission for Grace’s after school activities. She wants to play basketball and not soccer.
9:00 AM: Student is a no-show for meeting #1. Work on something called a “Grant Inquiry”, which basically requires me to fill out the exact same information as was already the full grant application, but in a new Word document. Feels like unnecessary busy work. Remember to call the dean today!
10:00 AM: Student meeting #2. Student arrives and I have a blissful 30 minutes of discussing only science. I love my students, and enjoy working with them towards their goals. Happy.
10:30 AM: Send grant inquiry to grants office for review. Start submission of a manuscript. Why are the journal submission systems so confusing? Need to fix keywords.
11:00 AM: Student meeting #3. Another 30 minutes of bliss. When will our new car get delivered? Call dealership. Delivery some time tomorrow.
11:30 AM: Continue submission. Manuscript needs to go through length check software. Internet goes down in the middle. Call Petter for advice.
11:45 AM: Internet back up. Restart submission process. Forgot to fix keywords! Restart again.
12:00 AM: See new summer interns in lab. Must ask them about their projects. Remember to call the dean!
12:30 AM: Submission almost ready. Email from Administration asking urgently for my Teaching summary from 2016-2017. Forgot to remind Petter about Grace’s after school activities – call and confirm pick up time at 4:30. Is basketball today or tomorrow?
1:00 PM: Submission ready! Minor error in manuscript formatting. Fixed. Don’t forget to call the dean! Also – need to discuss future of Coffee Board project. Important! Set reminder.
1:30 PM Manuscript submitted. Speak with interns briefly. See about setting up intracellular rig in lab. What is that DAQ board? I have not seen this type before. Ponder circuitry.
2:00 PM Skype chat with collaborator about new manuscript. Problems tying the story together. Some holes need to be fixed to get it past reviewers. Suggest a few more experiments. Need to get manuscript together – put on week’s to do list.
2:30 PM Rig not communicating with computer. DAQ board is very strange. Unfortunately, no time to think about it as have to prepare for next meeting.
3:00 PM Creche committee meeting, for which I am currently chair. 5 agenda items and discussion on refurbishment of creche. Requested renovations not allowed, need to restructure plans. Meeting interrupted by one of the member’s issue with bus drop off for their child. Forgot to call dean!
4:00 PM Reminded to process request for new computer since now USB and lightning ports are no longer working on laptop. Request quote from IT department.
4:30 PM Another faculty’s son shows up to volunteer. Quickly think of a small insect collection project he can do. Ask student about progress on intracellular rig. Remind another student to email collaborator.
5:00 PM Confirm Grace is home from after school activities. Start to look for Uber to go home.
5:30 PM Realize UBER is trying to find me a cab in Chennai. Wait for shuttle instead.
5:45 PM Shuttle. Think about dinner.
6:00 PM Home. Grace at birthday party since her homework is finished with Petter. Petter has also made dinner – he is awesome!
7:00 PM Send quotes to technician for help with computer purchase. Remind students about missing blog entries.
7:30 PM Put Grace to bed. She is angry that I have a volunteer and it isn’t her. Crying ensues.
9:15 PM Petter wakes me up in Grace’s bed where I have fallen asleep. Make sure permission slips and forms are in Grace’s backpack.
10:00 PM Go to bed, which involves a few more emails about meetings coming up and reminder list for next day – especially grant renewals!
11:00 PM Sleep. Good night.