Archive for the ‘Science’ Category

Overwintering

Friday, March 18th, 2016

Mourning Cloak

Early this month when I was at Ball Mill Resurgence Conservation Area, I noticed that there were a few butterflies around. This one was cooperative enough to land on a branch in the sun and let me photograph it. I didn’t know what kind it was, but I was surprised to see how worn it looked. Clearly this butterfly didn’t just emerge from a pupa.

I looked through my butterfly books, but couldn’t find it; I later realized that was because they’re much yellower when freshly emerged, fading to more white later. I posted it to the Butterflies of the Eastern US Facebook group, and within about 10 seconds I had a response; “Mourning Cloak”. And someone added, “they overwinter as adults.”

I was intrigued. In fact, I was shocked.  I realize that insects have to get through the winter somehow; beetles have larvae — grubs — that burrow in the ground, maybe some survive as eggs, that sort of thing.*  But an adult butterfly? Surely it would freeze. Even here it gets down into the single digits Fahrenheit — over 10 degrees C below freezing. How can they do it?

Not content to just wonder, I hit the literature. First I read about “freezing-intolerant” and “freezing-tolerant” insects. These were the accepted categories for overwintering insects at least into the early 1990s.    What I got from work by W. Block and K.B. Storey was that the former use antifreeze compounds to lower the freezing point of their cell contents, and survive as long as the temp doesn’t get below their supercooling point (SCP). The latter use nucleation compounds in their extracellular hemolymph to allow it to freeze while keeping the intracellular material from freezing.

But it turns out that it’s more complex than that. More recent work, summarized in 1999 by Brent Sinclair, puts all of these on a continuum. Most insects use both antifreeze compounds and ice-nucleating compounds in some combination. They lower their freezing temperature, but then they may also be able to survive below the SCP when actually frozen.

The butterfly in the photo, the Mourning Cloak – Nymphalis antiopa, is a member of the family Nymphalidae. While most Lepidoptera overwinter as larvae or in some cases eggs, many Nymphalids overwinter as adults. They crawl under leaf litter or under loose bark and wait for spring.

The Mourning Cloak doesn’t freeze until -20 C, and it can survive temps down to -34 C — well below any recorded temp in this area. To me it’s pretty astounding. These guys sit there and freeze solid in a cold winter. Then when it warms up, they thaw out, crawl out of where they were hiding, and fly away.

So which of the butterflies you’re seeing sat out the winter as adults?  “Hibernal Diapause of North American Papilionoidea and Hesperioidea,”** a 1979 review by James Scott, includes a handy table  listing each species’ hibernal diapause stage as E, L, P, or A (egg, larva, pupa, adult), with references to back them up.  For me in Southeast Missouri, the take-home message of the table is that Red-Spotted Purples and most Fritillaries overwinter as larvae, Swallowtails overwinter as pupae, and Brushfoots mostly overwinter as adults.  So the adults that overwinter that I’m likely to see include the Mourning Cloak; genus Polygonia – the Comma and the Question Mark; and genus Vanessa – Painted Lady, American Lady, and Red Admiral.

Question Mark

Polygonia interrogationis, the Question Mark

Eastern Comma

Polygonia comma, Eastern Comma

Red Admiral

Vanessa atalanta
, Red Admiral

Butterfly on lantana

Vanessa cardui, Painted Lady

*The process of getting through a cold winter by slowing down body processes and waiting somewhere is loosely called “hibernation” in insects.  More properly, it’s referred to as “hibernal diapause”.  Some insects have a quiescent stage when it gets too hot as well, which is “estival diapause”.

**The Papilionoidea superfamily includes all the butterflies except the skippers, which are in the Hesperioidea.  So together those superfamilies constitute “butterflies”.

NOTE: One more local butterfly that overwinters as an adult is the Sleepy Orange, Eurema nicippe.

Caster Semenya and the problem of gender

Saturday, August 22nd, 2009

Semenya
As everyone has probably heard by now, champion runner Caster Semenya is being tested by the IAAF to see if she is actually qualified to compete as a woman.  The issue is complex.   During the Cold War, olympic athletes were tested, first simply by visual inspection, and later by examining their chromosomes.   The testing is now done by a panel, including various medical specialists as well as a psychologist.  How they arrive at a decision is not obvious.

Nor should it be.  The real issue here is that gender is a continuum, or more properly a whole set of continua, and the rules of sport treat it as a dichotomy.  What does it mean to be female or male?  What is gender?

Psychologists and physicians recognize a number of components to gender.  Here’s an incomplete list:

  • Genital — does the individual have a penis and scrotum, or a clitoris and vulva?
  • Chromosomal — XY or XX?
  • Hormonal — high levels of androgens or estrogens?
  • Gender identity — does the individual perceive him or herself as male or female?
  • Sexual orientation — is the individual sexually attracted to females or males?

It should be obvious on reading the list that all of these have the potential to be answered “neither” or “both” or “in between” in some cases.  And, although the items on the list aren’t independent of each other, they’re not absolutely linked either.

A quick review of sex determination in mammals:  In mammals, the default development schema is female.  All embryos start out with a cloacal opening that eventually divides into the anus and another opening.  The second one becomes the vagina in females.  If a Y chromosome is present, at about 10 weeks after fertilization a gene on the Y (known as SRY) is expressed.  The product of this gene is a regulatory protein (also known as SRY) that causes the development of glandular tissue in the sides of the opening — the area that will become the labia in females.  The glandular tissue produces testosterone, a steroid hormone that controls expression of lots of genes.  One consequence of testosterone production is that the labia majora thicken and fuse, closing the vaginal opening.   The labia minora also fuse, forming a tubular sheath around the urethra.  The urogential tubercle, a small swelling at the top of the opening, enlarges in response to testosterone and becomes the glans of the penis.   Without SRY, none of this occurs.  The urogenital tubercle remains small and becomes the clitoris, and the labia remain separate on the sides of the vaginal opening.

Fetal genital development

Fetal genital development

There’s a range of “normal” responses to SRY, so that different individuals will have varying amounts of testosterone production.  There’s a range of “normal” responses to testosterone, so that different individuals with the same testosterone levels will show different levels of expression of the genes that are regulated by it.  This means, among other things, that the clitoris can vary in size, as can the penis.  It means that around 1 to 4 % of male babies are born with incomplete closure of the penile shaft, leaving an opening on the underside of the penis; this condition, known as hypospadias, has increased in frequency in recent years.

Testosterone binds in the cell to a protein called the androgen receptor, which then binds to DNA and affects gene expression.  Androgen receptor proteins vary, as does their effectiveness in mediating testosterone’s effect.  Individuals who lack functional androgen receptors are said to have androgen insensitivity, and XY individuals with this condition may produce lots of testosterone but develop (at least superficially) as female.

Androgen insensitive XY siblings

Androgen insensitive XY siblings

I once was explaining this to a class, and after seeing this textbook photo, a student asked “Couldn’t that lead to homosexuality?”  I initially thought she meant that, being XY, they’d want to have sex with women, and that would make them lesbians.   It took a few minutes of rather confusing discussion before I realized that she meant that they’d probably have sex with guys, and being XY, that would make them gay.    I think the class found it fairly disturbing that their terminology wasn’t working in this instance.

Androgen insensitivity and hypospadias are examples of the range of conditions known as intersex.    The term itself reflects the general discomfort of people toward any admission that gender is not an absolute dichotomy.  And of course, that discomfort exists in part because a large majority of individuals do cluster close to the ends of the continuum, at least when it comes to genital morphology.

When you consider, as discussed in the recent New York Times essay on this issue, that muscular development is strongly influenced by testosterone levels and the efficiency of the testosterone regulatory response, and you consider that both of those vary considerably in individuals of either gender, it becomes clear that the IAAF is trying to fight a losing battle.

Inevitably, in many sports where amount of muscular development is important for success in competition, the women’s competitions are going to be dominated by individuals who happen to fall just as far  toward the “masculine” end of the various continua as the rules committee will permit.  When there is no absolute standard, but rather some sort of consensus based on a panel of experts in various fields, it’s going to be a messy process, and some people are going to feel that they’ve been treated unfairly regardless of what the decision is.

Intelligent Design makes a testable prediction …

Friday, July 3rd, 2009

As pointed out in numerous blogs  and at least one Wikipedia editor’s user page, the clock is running out on this dire prediction from the éminence grise of ID:

“In the next five years, molecular Darwinism—the idea that Darwinian processes can produce complex molecular structures at the subcellular level—will be dead.”

William Dembski, Touchstone magazine, July/Aug 2004

I guess we’ve got a month or so before the whole evolutionary house of cards collapses.  Of course, the fact that Google Scholar gives 579,000 hits since 2004 for “molecular evolution” suggests that Dembski might turn out to be wrong.  I’m holding my breath.

Curious conjunction of circumstances

Thursday, February 5th, 2009

My phone rang this afternoon, and it was Cabell, on the way to teach human sexuality, asking me about a certain reputedly intersex actress.  We had a brief conversation about androgen insensitivity.  This is a condition in which an individual has a mutation in the gene that codes for the testosterone receptor protein.  The individual makes testosterone, but the cells don’t respond to it at all.  As a result, an XY individual with this mutation develops as a female in most obvious ways.  External genitalia appear female, and at puberty she develops breasts, etc.  Typically such individuals are tall, relatively broad-shouldered and narrow-hipped, and have larger than average breasts.  They are generally sterile, and the vagina may be shallow.

Famous pic of four XY siblings with androgen insensitivity (NSFW, unless your work relates to genetics or sex determination).

Of course, I’m talking about this in my office at the Center for Writing Excellence, which is basically a cubicle — everyone in the place can hear me talking about naughty bits, and I’m not safely in my biology environment.  Whatever; they’ve come to expect this sort of thing from me.

Okay, so then later in the day I’m looking at facebook, and a friend has posted a link to this site with pictures of redneck wedding cakes.  The first cake pictured:

Shows two deer on the top.  Several commenters pointed out that both have antlers, and wanted to know if these were San Francisco rednecks, etc.   Another commenter says that females can have antlers.  So I checked it out, and found this article about does with antlers, which are rare.  Why do they occur?  Oh, various reasons, such as intersex, …

Seems like today is intersex day for some reason.

I’m famous.

Tuesday, November 18th, 2008

Walt and I were looking at the county-by-county electoral map on November 6, and saw that curving blue line across the deep south.   I said, “What the hell is that?  It’s got to be some kind of geographic feature.”  We looked in Google Earth and didn’t see anything obvious, and then I got an idea and googled “Cotton Production 1860″.   Voila, the maps match perfectly.  I cropped the national electoral map to match the cotton map and put them both up on a page that very afternoon.

See this post on Wonkette, titled “Slaves vote heavily in Obama’s favor?“   Wonkette got it from Andrew Sullivan, who got it from Strange Maps, who got it from Pin the Tail, who apparently got it from me and posted it a week after my page went up.

Update: After this post went up, both Strange Maps and The Vigorous North cited my original post.  They also add considerable interesting content, and The Vigorous North traces the landforms and soil types responsible for this pattern back to the late Cretaceous shoreline.  Worth a look.

Update to the Update: Now featured on Rachel Maddow’s blog as part of an even more comprehensive discussion.

Earthquake

Friday, April 18th, 2008

I woke up this morning at 4:36 AM because the house was shaking.   It wasn’t all that strong, but lasted surprisingly long.  At least 15 seconds after I woke up, and from what I hear, that was halfway through it.  The windows rattled, and I said “Is it an earthquake?” to Robin, who agreed it was.  Then we went back to sleep.

It wouldn’t be news if this one happened in California, only magnitude 5.4.  We don’t get many around here, though.

I’m so proud to be a Floridian.

Tuesday, February 19th, 2008

The Florida board of education just passed new standards that for the first time require teaching of EVIL-lution. However, only over this guy‘s objections.

Ganked from Think Progress, which has more details.

Oh, and here’s an editorial by Carl Hiaasen about the issue.

And I cannot tell a lie, I found out about this, as I do most of my news, by reading Wonkette.

Cool video

Thursday, February 14th, 2008

I’ve probably shown this to lots of people, but this video of cell biology is just really damn cool. Everything in it is consistent with the best models supported by current research, including the little kinesin proteins walking along the microtubules pulling vesicles. If you know some cell biology, it’s fun to watch and figure out what all the things are. If you don’t, it’s still pretty fun to watch.

My only caveat is that some stuff is too directional — when the tubulin proteins assemble to form a microtubule, they don’t swim toward the tip of the growing microtubule. They’re all in there bouncing around randomly, and when they HIT the tip of the growing microtubule, they stick. There are several examples in the video of this kind of directional movement that should actually be random. Easier to animate, I suppose.

More idiocy in the Missouri legislature

Friday, April 13th, 2007

Genetics Exam 2:

1. Explain the process of rho-dependent transcription termination in E. coli.

The Flying Spaghetti Monster pulls the RNA off the template with His Noodly Appendage.

***************

If the legislature gets its way, I won’t be able to count off for this answer.

The state House has given initial approval to an “intellectual freedom” bill that would require all state educational institutions to establish policies to ensure that students aren’t coerced into beliefs they disagree with.

Here’s an excerpt from the bill (HB213):

2. The coordinating board for higher education shall require each public institution to report annually to the general assembly detailing the steps the institution is taking to ensure intellectual diversity and the free exchange of ideas.

(1) The report required in this subsection shall address the specific measures taken by the institution to ensure and promote intellectual diversity and academic freedom. The report may include steps taken by the institution to:

(e) Include intellectual diversity concerns in the institution’s guidelines on teaching and program development and such concerns shall include but not be limited to the protection of religious freedom including the viewpoint that the Bible is inerrant;*

Now, I teach a science and religion class in which I work very hard to be respectful and accommodating of different beliefs, but I insist that students deal with the scientific evidence in a reasoned way.  With the legislature breathing down my neck, I don’t know that I could teach that class.  For that matter, the introductory course for biology majors is an evolution class.  Can we set any standards at all for intellectual rigor, or is “diversity” going to trump everything else?

I’ve taken the liberty of writing a draft University policy to meet the requirements set out in the bill explicitly.

*Yeah, I know that (e) has syntax problems. The least of our worries, OK?

What, if anything, is a reptile?

Monday, April 2nd, 2007

Reptiles don’t exist.