The living rainbow: “Masculine” is actually “territorial” in electric fish

ResearchBlogging.orgOne of the most interesting ideas in Joan Roughgarden’s book Evolution’s Rainbow is that across the animal kingdom, many behaviors that we associate with gender—aggressiveness in males, nurturing of young by females—do not line up with biological sex as cleanly as we might think. One good example I’ve discussed before is white-throated sparrows, a species in which either the male or the female in a mated pair can take the aggressive role of defending the pair’s nesting territory.

That principle is echoed in a paper recently published in the journal Behavioral Ecology and Sociology. This time the subject is not birds, but electric fish. Electric fish generate, and can sense, weak electric fields, which they use to navigate their environment—and for social signalling.

Here’s video of a male and female of the species Brachyhypopomus pinnacaudatus interacting, via the website of Philip Stoddard, the senior author on the new study. The fishes’ electric fields are made audible in the soundtrack, as sort of scratchy noises.

Male and female electric fish typically generate detectably different electric signals. However, Stoddard’s team have found some evidence that “masculine” electrical signals may be more generally associated with aggressive social interaction for eletric fish of both sexes—in more crowded conditions, female electric fish start to signal more like males.

The team recorded electric signals from the electric fish Brachyhypopomus gauderio in both a natural population in Guatemala, where population density varied over several sampling periods, and in the lab, under experimentally varied population densities. In both the field and the lab, female fish generated signals with greater amplitude—a “masculine” signal trait—when the population density was higher. Females also generated signals of longer duration—another “masculine” trait—when the ratio of females to males in the population was greater.

Blood tests on female fish in the field study found increased levels of testosterone—which has previously been connected to more “masculine” electrical signals—associated with a higher female-to-male ratio. However, this wasn’t replicated in the lab study.

So it looks like the female fish in this study use the same kind of signalling for aggressive social interaction that males do. That suggests the general differences between male and female signals are more due to differences in how often each sex interacts aggressively than because of physiological differences between the sexes per se.◼

Reference

Gavasa, S., Silva, A., Gonzalez, E., Molina, J., & Stoddard, P. (2012). Social competition masculinizes the communication signals of female electric fish. Behavioral Ecology and Sociobiology DOI: 10.1007/s00265-012-1356-x

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The Best Online Science Writing 2012 is now available for pre-order

For instance, over at Powell’s Books.

This edition includes my long piece on natural selection and human sexual minorities, alongside many other, arguably more worthy, selections from last year’s crop of online science writing, including top-notch work by Crystal D’Kosta, Kate Clancy, Carl Zimmer, Deborah Blum, and Steve Silberman, among many others.

Thanks to Eric M. Johnson, whose great and timely essay “Freedom to Riot” is included in the collection, for the head’s up!◼

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Required listening: Armistead Maupin on the President’s marriage statement

Woke up to this on NPR this morning: Writer and activist Armistead Maupin, discussing President Obama’s big statement on marriage equality with “Weekend Edition Saturday” host Scott Simon.

Well, we talk about bullying a lot in this country as if it’s something that’s generated in schoolyards, but in fact it’s generated in churches, and by politicians—by parents, even, who don’t even consider the fact that their own children might be gay. So when something like this comes from the top, from the very top, it’s gonna filter down. It can’t help but filter down.

We can certainly hope it will. Maupin also touches on his relationship with a conservative, Republican-voting brother in North Carolina.◼

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Terry Gross after hours

Yesterday I saw the latest live presentation of “This American Life,” as broadcast to a multiplex in Minneapolis. Jealous? You should be. Because it was awesome.

But fortunately, one of the best segments, a short film by the comedian Mike Birbiglia, is now freely available online. It’s … probably not describable without spoiling it. Just watch, already.

Birbiglia’s upcoming movie looks pretty good, too.◼

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Science online, colony collapsing crocodiles edition

Bees: still not doing well. Photo by net_efekt.

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Nothing in Biology Makes Sense: Making sense of polar bears’ origins

Polar bear. Photo by ucumari.

This week at the collaborative blog Nothing in Biology Makes Sense, contributor Noah Reid goes in-depth on the recent study pinpointing the historical origins of polar bears, and why it’s taken the most recent systematic methods to correctly pinpoint them.

From 2008 to 2010, a series of algorithms were published that could take data from multiple genes and infer the history of whole populations, a drastic improvement over previous methods that could only identify the history of single genes (e.g. mtDNA). With these methods in mind, a group of researchers gathered data from 14 nuclear genes for multiple extant brown and polar bear populations (Hailer 2012). … the new data analyzed with the new method suggested that polar bears diverged far earlier than previously thought (around 600 thousand years ago) and that they were no longer closely related to the southeast Alaska population, but rather to the common ancestor of all brown bear populations.

For more details, including a nice brief explanation of why it can be important to use multiple genes in reconstructing relationships among species, go read the whole thing.◼

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The Three Laws of Mitt Romnics

Mitt. Photo by davelawrence8.

Following up on my tweet from yesterday, here’s my best guess at the Three Laws of Mitt Romnics. (With deepest apologies to the memory of Isaac Asimov.)

(1) Mitt Romney may not injure a corporation or, through inaction, allow a corporation to come to harm.
(2) Mitt Romney must obey the orders given to him by conservative Christians, except where such orders would conflict with the First Law.
(3) Mitt Romney must protect his own integrity as long as such protection does not conflict with the First or Second Laws.

In the spirit of nerdy completeism, the Zeroth Law of Mitt Romnics is, of course: Do whatever it takes to get elected President.◼

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Evolution is undirected, political evolution doubly so

Pioneering gay rights activist Frank Kameny, at a White House event to commemorate his work. Photo from the White House photo stream.

To everyone wringing their hands over the Obama Administration’s weird collective dance around the question of marriage equality: You do know that evolution is an inherently undirected, frequently random, ultimately goal-less process, right? In which case, the President’s description of his position as “evolving” is an exceptionally apt fit for the inefficient waffling, contradictory signals, and even reversal of previous positions that we’ve observed over the last several years.

See, doesn’t that make you feel better?

Yeah, me neither.

How about this as a kicker instead: evolutionary changes that appear to be directionless over short periods of time may eventually turn out to be part of much longer-term trends.◼

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And another thing …

Regarding that adaptive fairytale about the “runner’s high”—over at Distributed Ecology, Ted Hart points out that it doesn’t make much sense in phylogenetic context, either.

What would be really interesting is to see where this trait maps across the phylogeny. Is it a conserved trait that was selected for in some ancestor? That would point to the fact that maybe it has nothing to do with running. The authors are mute about phylogeny, but eCB’s could alternatively be the ancestral character state, and really the interesting question is why did ferrets evolve the loss of this state? On the other hand maybe the trait evolved multiple times, and that also is really interesting to ask how that happened. But either phylogenetic scenario undermine the central thesis of Raichlen.

You’ll want to read the whole thing, natch.◼

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