Q&A: Meet A Real-Life “Spider Woman” Who Makes Cell Biology Less Scary
To bring the mysteries of cytogenetics to life, Dr. Leocadia Paliulis has her students capture their own specimens-especially spiders.
By Tony Farrell · March 5, 2020
Leocadia “Le” Paliulis, PhD
Many humans are familiar with the XY sex-determination system, wherein XX and XY chromosome patterns divide us neatly into female and male categories. However, that is not the only system in the animal kingdom. In fact, there is a huge range of chromosome-based sex-determining systems among earth’s creatures.
That is great news for researchers such as Leocadia “Le” Paliulis, PhD, a professor of cell biology at Bucknell University in Lewisburg, Pennsylvania. Paliulis focuses her studies on cytogenetics-the behavior of chromosomes in cells. And when it comes to sourcing those cells, well, it only gets more interesting. She focuses her studies on what might be one of the most undeservedly unpopular creatures: spiders.
Course Hero recently connected with Dr. Paliulis to learn why she seized upon these arachnids as ideal “subjects,” how she catches and uses them in her Cytogenetics course, and how her students respond.
See resources shared by Leocadia Paliulis, PhD >>
Context
“There is always something fascinating to find, no matter where you live. You will always find a spider or an insect that has something of value to study.”
- Leocadia Paliulis, PhD
Course: BIO 326 Cytogenetics
Course description: Study of chromosome structure, organization, aberrations, and behavior. Multiple eukaryotic systems will be considered with links to human disease.
Paliulis’s approach: Using spiders to teach cell science
Before Paliulis began studying spiders, she used grasshoppers and a variety of other systems to investigate chromosome segregation. “Then, shortly after I started working at Bucknell, a student came up to me and said, ‘Hey, there are a lot of spiders outside my dorm right now, and I’m really interested in looking at their chromosomes.’” As she and her student started studying the spider chromosomes, Paliulis realized that spiders were really very special.
Below, Paliulis shares what she learned-and what happened next.
Course Hero: What makes spiders an easy subject for students to study?
Leocadia Paliulis, PhD: Arthropods in general have cells that are easy to work with, so you can use them to study chromosome segregation and, in particular, meiosis-the type of cell division responsible for making sperm and eggs. You can look at meiosis in spiders in a really beautiful way because the cells are easy to isolate, are large, and are easy to visualize.
And I would argue, with some good support, that spiders have the widest variety of different sex-determining mechanisms-multiple X and multiple Y chromosomes. So it’s a huge, huge range, and what that means for me in the lab is that these offer me an opportunity to study things like how forces are balanced on chromosomes.
One other benefit is that these cells work well for micromanipulation. I can stick a tiny glass needle into cells and push the chromosomes around, reposition them into different places, apply tension to them, measure forces on the chromosomes-things like that. And that can really only be done in arthropod systems.
What did you discover when you started to look at the arachnid chromosomal structure?
In a human cell, you have two partner chromosomes that align in the middle of the mitotic spindle during mitosis. They attach to two different sides of the spindle, and they get pulled apart. But what if you have three? How do you balance those three chromosomes that are aligning?
Well, it turns out from our observation of spiders that these also align at the middle of the spindle, but instead of having one on one side and another on the other side like a tug of war, you have two on one side. You would think that would be totally unbalanced, but it turns out it’s not.
So that’s one thing-forces balance-that we have been studying. But it turns out there are other things, too. It turns out that a Y chromosome is pretty rare in spiders, and we’ve discovered really new instances of Y chromosomes cropping up throughout the spider lineages that are very cool. There’s just such a huge variety of fabulous behaviors that we’ve been studying in my research lab.
How do you go about finding spiders for students to study?
We’ll go outside and collect our spiders. Sometimes we’ll sneak into basements and other places where we can catch them. Especially if there’s a dirt floor in a basement, there are probably centipedes that are food for cellar spiders. And we capture them in those deli containers that you’d buy soup in.
For grasshoppers in the field, we’ll use sweeping nets to capture them, because they’re so much faster than spiders. I send students out into the field to see what we can find, and we work with whatever we catch. So we’ve been having a lot of fun with different species of grasshoppers, beetles, and things like that-and just exploring new information.
Sometimes I order spiders from suppliers, and that’s kind of a new and really nice thing, too. I’ll buy 50 male black widows, and they’re in the mail the next day. But I don’t use those for my classes!
How do the students react to studying spiders and other bugs?
Some of the students are afraid to touch the bugs. Some students might be holding a cricket forever-or they can’t hold it, and they’re so nervous that it jumps out of their hands. Sometimes they’ll scream, and they’ll drop the spider, and I have to chase it. But I’m pretty quick about preparing for experiments, because the quicker you are, the healthier your cells are.
I have students who are sort of scared pair up with someone who has more confidence, and that works pretty well. We are careful, and we wear gloves, too.
We do not typically use spiders that are dangerous or will cause any problems. I’ve never had a bite or a sting. And dangerous spiders, like the brown recluse or black widows, actually are rare and hard to find. They’re called brown recluse for a reason!
What is the last step before students look at spiders on a chromosomal level?
To prepare spiders for dissection, you can gas them with carbon dioxide to anesthetize them and then dissect them to obtain the tissues that you need. Or you can “cold-shock” them by putting them in the freezer briefly-which does not kill them but knocks them out within about five minutes-so you have to do your dissection very quickly.
It’s sad because we all grow to love the organisms that we work with. I don’t particularly like killing the organisms to do my experiments-I don’t like that at all, actually-but I do see that there is so much value, so much to be learned.
Originally published at https://www.coursehero.com on March 5, 2020.
