Science, why you gotta do me like this?

“It would be cool to map the appearance of a pigment pattern,” I said. “Just photograph spider abdomens over development,” I said. “It’ll be easy,” I said. “Just do it!” I said.

So I took these Steatoda triangulosa embryos that emerged from their egg sac yesterday, and I sat down at my microscope and configured my camera to a useful and consistent setting (with a little tinkering, I found I could get decent photos at f/4, 1/80th of a second, ISO 3200 (!), at 64x on my Wild dissecting scope), lined up the containers with the spiderlings next to me, and thought I’d just march through and snap photos of the dorsal surface of the abdomen. Then I’d repeat this procedure every couple of days, and at the end of it all I’d have photographic series of pigmentation changes over time in a developing set of spiders. Simple! Except…reality intrudes.

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Steatoda triangulosa!

I said I was going to tend to my shiny newborn Steatoda triangulosa today. It didn’t take as long as I expected. Here’s the vial of my freshly emerged spiderlings; the egg sac is the foamy looking bubble at the bottom, attached to the yellow plug on the vial, and the little dots are the babies.

There were only nine spiderlings from that egg sac. It was a bit of a surprise, since when a Parasteatoda egg sac pops, I easily get over a hundred spiderlings. It makes me wonder how well S. triangulosa does in the wild — I can tell you from our summer survey that they were the rarest of the false widows we found, with even S. borealis far more numerous, and they were a distant second to Parasteatoda. Now I’m curious about what niche they fill in the local spider ecosystem.

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Chemistry and triangulosa

Work is heating up as it always does in the first few weeks of classes. Today and Friday I’m blitzing through a basic chemistry review in cell biology, because…biology is all chemistry. A very narrow and specific domain of chemistry, sure, but if you don’t understand how electrons flow you’re getting nowhere in cell biology. Yesterday was spent re-reading a lot of introductory chemistry stuff to remind me of how this all works, today I lay it all out for the students, who might be bored, but still a bunch of them will mess up on the easy chemistry questions in the first exam.

It always shocks incoming students who think biology is all frog dissections and memorizing organs. Nope, all chemistry, and in order to get the chemistry, you need to know the math. So all you high school kids thinking it would be neat to major in biology and play with spiders, buckle down and learn your basic algebra and pre-calc, at the least, and work through chemistry and physics.

Then I have some lab stuff to do. Today I’m going to focus on our Steatoda triangulosa. We’ve got a few young second generation juveniles coming up that I need to sort into larger quarters, and another egg sac that is full of baby spiders. The cool thing about S. triangulosa, besides the pretty pigment patterns, is that their egg sacs are fluffy, loosely woven silk and are semi-transparent, so you can see the eggs right through them, and right now I peek in and it’s a mass of writhing spider legs, so they’re about to emerge, I’m sure. The less cool thing about them is that they seem to be slower to develop, and for at least the one mama I’ve got in the lab, lay a smaller number of eggs. I might have to go hunt down some more adults so I have a larger sample before the frost hits.

Anyway, I’ll take pictures! I think I’ll post a purely S. triangulosa article later today.

But first, chemistry! That’s my day sorted.

Bee-killer

It begins with the screaming of the bee. We looked down into a flower patch, and there was an innocent honeybee, snared in a spiderweb, twirling maniacally and buzzing frantically as it struggled to get free. Mary told me to free it…I said “No,” callously.

I followed the lines of the web, a rather tattered orb at this point, and found what I was looking for — the claws of the predator, peeking out from under a leaf.

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Walking with spiders

I went for a walk in lovely downtown Morris today, and was rather disappointed. Tegenaria has taken over! Where earlier this summer I would have found the delicate, airy cobwebs of my favorite false black widows, there was nothing but these thick, dense sheets of webbing leading to tunnels of silk with these massive spiders lurking within.

OK, fine, they’re still spiders…but they’re far more shy than Parasteatoda. I’d gently and slowly ease my camera lens towards them, but long before the spiders were in focus they’d dart deeper into the tunnel. It was frustrating. I started seeing the utility of this probe lens.

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Spider Friday

One of the benefits of my job is that I get to work with young men and women all day, except when I’m not, when I’m puttering about with spiders (we will pretend committee meetings do not happen). So this morning I had my coffee and then toddled off to the lab to tend to my little friends.

Here’s my breeding colony.

They’re the ones with special privileges. They get the big roomy 5.7L sterilite containers, with one female per cage and connubial visitations. There are also racks in a pair of incubators with about 50 more spiders living in 3cm diameter tubes; they seem content, as long as food keeps getting delivered. So some of the spiders get to live in a suite at the Hilton, others are in the capsule hotel.

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Growing up is tough for a spider

I mentioned a while back that we had this surplus of spiderlings and that we were going to do some measurements of survival under different population densities. Well, we’ve got two weeks of data now, so we can think a bit.

It was a simple experiment: we put different numbers of recently emerged spiderlings in two different sized containers. We had 5, 10, 15, or 20 spiders in containers that were either about 100ml in volume, or 5.7 liters, so spider density ranged from 0.0009 spiders/ml for the big, nearly empty containers to 0.17 spiders/ml in the small overcrowded ones. We’re basically asking how crowded to they need to be to start affecting each other’s survival, and what’s the greatest density we can get away with, anticipating that no matter what, some will die. And the answer is…

Density doesn’t matter. It didn’t matter how many spiders we started with, or whether it was a small or large container, we ended up with 1-3 spiders in a container at the end of two weeks. You start with 10 in a giant container, you end up with about 3; you start with 20 in a tiny box, you end up with about 3. They’re all spaced out, too; we found that individuals tended to occupy different corners, no matter how much room they had. There were no containers which had 100% mortality.

What does that look like? They seem to be murdering their siblings to set up exclusive territories. Ah, the life of an adolescent spider. What it means is that only about 20% of the spiderlings have survived this battle royale so far. Maybe eventually they’ll be reduced to one spider per container.

Dang. Next experiment is to set up containers for individual spiderlings to see if that increases the overall survival rate. If it does, then I’ve got to do some more thinking. I can’t possibly accommodate every spiderling produced by a parent, since that would mean I’d have 150n spiders in n generations, with a generation time of about a month, so in a year I’d have 1026 spiders, which would mean I’d have to pack about 1012 spiders per square meter of Earth’s surface area, and I’d have to take over the earth to provide housing for my brood. Oh, man, and all the flies I’d have to raise! Sorry, everyone, I’m going to have to draft everyone on the planet to help maintain my spider colony.

Alternatively, I have two more modest strategies. A) I handpick the small number of spider babies I need to repopulate my colony and maintain the population size, which would require raising their offspring in individual containers. Or B) I put a small number, say 10, spiderlings in small containers, expecting that most will die in a vicious battle royale, and only one can survive in each container. There can be only one! But that one will be the most savage, ruthless spider of the group. It’s mollycoddling vs. natural selection.

Maybe I can do both for a while and see which strategy leads to the healthiest next generation.

One worry is that (B) might lead to the total extinction of all males, since the females are bigger. In nature they can disperse far apart, so we don’t have as much fratricide/sororocide, other factors will cull them. Get males from population A, and females from B? This sounds like another experiment.

Fierce mama

Yesterday, we let Iliana play in a cardboard box. But before we could do that, we had to clear out the spiders that had rapidly colonized it first, and that’s how we caught this nice Parasteatoda. Last night, while we slept, she spun an egg case and laid a lot of eggs in it, and then today, I had to put her in a different container. She would not go. I tried every trick in the book to separate her from her egg case, and she would frantically scurry back up into the vial. Then I tried removing the egg case; no go. She had it tethered, and as soon as I got it away, thwip, she’d reel it back up. I had to give up and let her stay with her eggs. These spiders are extraordinarily maternal.

Nope, I’m not going to battle that to get her treasure. My party is going to have to level up a lot more.

We have a plethora of spiders now!

I’ve got one baby at home, and today when I came in to the lab we found even more babies…cute little spider babies. It seems this was the weekend almost everyone decided it was time to emerge from the egg sac, and seven egg sacs spewed out clouds of spiderlings.

This is a little overwhelming. I spent a few hours separating out spiderlings and trying to spread out the masses to more containers.

Here is the maternity ward. See all those vials with foam plugs? Each one contains a female spider and one or more egg sacs. If you look closely, you can see lots of little dots, and that’s the cloud of new babies. That’s probably a thousand spiders you’re looking at.

Let’s zoom in a little on one of the vials.

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