Drop your weapons! Autotomy, the shedding of a body part, reveals the hidden cost of conflict

November 15, 2018, Smithsonian Tropical Research Institute
Male, leaf-footed bugs, Leptoscelis tricolor, with wings open as in flight. Ummat Somjee, Tupper post-doctoral fellow at the Smithsonian Tropical Research Institute studies the hidden metabolic cost of maintaining weapons like the large, spiny hind legs of these insects. Credit: Ummat Somjee

Animal weapons such as antlers, tusks and limbs specialized for fighting require a large energy expenditure to produce and may cost even more to maintain. Because the leaf-footed bug sheds its large hind limbs, used as weapons in male-male battles, scientists working at the Smithsonian Tropical Research Institute (STRI) in Panama could measure energy use of live bugs with and without hind legs to calculate the hidden energetic cost of weapons' maintenance.

Wild animals can spend up to 30 and 40 percent of their total energy budget while at rest. "Human athletes often burn more calories during their relatively long rest periods than during physical exercise itself," said Ummat Somjee, who did this study as part of his doctoral dissertation at the University of Florida in co-author Christine Miller's lab group and is currently a Tupper post-doctoral fellow at STRI.

"We calculated the metabolic cost of maintaining large hind legs in a leaf-footed bug and found that males invest more in weapons than females do," Somjee said. "Large males expend relatively less energy on their super-sized weapons than smaller males." The results are published online in Proceedings of the Royal Society B.

Male -footed bugs, Leptoscelis tricolor, hang out on bright orange or red heliconia inflorescences, feeding on nectar and developing heliconia fruit. Their hind legs, covered with thorny structures, are larger than females' legs and serve as weapons in male-male duels.

"By dissecting legs and staining the tissue, we showed that the insects' tough exoskeleton is filled with metabolically active muscle tissue," said Meghan Duell, doctoral student at Arizona State University and co-author. "We realized that because these bugs shed their when molting or trapped, we could simply measure carbon dioxide production rates before and after a bug shed a leg to see how much was being expended on maintaining it."

Because leaf-footed bugs lose their legs, it is possible to calculate the hidden cost of maintaining a weapon. Credit: Ana Endara, Smithsonian Tropical Research Institute

The team discovered that the resting of one-legged bugs dropped by almost a quarter of the total (23.5 percent) in males and 7.9 percent in females. Heavyweight males had less of a drop in metabolic rate per gram of leg lost, indicating that the price of a big is energetically lower than it is for light-weight .

The largest deer develop especially enormous antlers for their and the biggest elephants have relatively heavier tusks than smaller individuals, but it is not known how energetically costly these structures are in most organisms. "Metabolic costs like these could be important in shaping the evolution of these diverse structures," Somjee said.

Explore further: Male elk face a trade-off regarding when to drop their antlers

More information: Ummat Somjee et al, The hidden cost of sexually selected traits: the metabolic expense of maintaining a sexually selected weapon, Proceedings of the Royal Society B: Biological Sciences (2018). DOI: 10.1098/rspb.2018.1685

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JaxPavan
3.7 / 5 (3) Nov 15, 2018
My sense is that evolutionary biologists do not give enough credence to sexual selection as an evolutionary tool (beyond simply speeding the adoption of otherwise beneficial survival mutations).

For example, half-evolved, nonfunctional wings would certainly be a crippling disadvantage selected against over many, many generations of evolution.

But suppose arguendo, a bipedal species that used bright feathers on its forelimbs to signal and aid in a competition with other males to jump the highest above grasslands, to attract a mate looking for the brightest feathers and the highest jumper. . .

Might account for why evolution has created flying animals but not dirigible plants.
jonesdave
2.6 / 5 (5) Nov 15, 2018
My sense is that evolutionary biologists do not give enough credence to sexual selection as an evolutionary tool


Disagree. There is shed loads written on the subject. It is a balance between sexual selection and survivability. Check out the peacock's tail, for instance. As long as the male lives long enough to mate, then happy days. If it gets caught by a tiger, tough sh!t. Over millions of years, this will be selected for and against.

jonesdave
1 / 5 (3) Nov 15, 2018
There is a very good educational video on why losing body parts is not necessarily fatal in a battle;

https://www.youtu...Tci1Bunk :)
JaxPavan
3.7 / 5 (3) Nov 15, 2018
@jonesdave

You missed my point entirely. You seem very stuck in whatever are the conventional prevailing scientific opinions. Ultimately, a very unscientific mindset.

I'm talking about sexual selection as an evolutionary tool for bridging gaps that would otherwise be impossible for incremental selection to bridge. I give flight as the most obvious, but there are many instances of organs that would be a huge disadvantage to survival until fully evolved.
jonesdave
2.3 / 5 (6) Nov 15, 2018
.....but there are many instances of organs that would be a huge disadvantage to survival until fully evolved.


Your brain is presumably fully evolved. It isn't helping is it?

Ojorf
3 / 5 (4) Nov 16, 2018
sexual selection as an evolutionary tool for bridging gaps that would otherwise be impossible for incremental selection

I can see how sexual selection can push an animal to somewhere on the evolutionary/genotype/phenotype landscape it would not otherwise have reached purely by other selection pressures.
Usually (allways?) though the trait selected for indicates superior health/strength in the animal, because it is a handicap that needs to be overcome.
Somehow that handicap needs to become an advantage.
I give flight as the most obvious, but there are many instances of organs that would be a huge disadvantage to survival until fully evolved.

I don't think flight is a good or obvious example at all. Sexual selection probably played a minor role in the evolution of flight, if any. I think the pouncing proavis model has the greatest amount of concrete evidence .
There is another problem, sexual selection selects for traits in only one of the sexes.
TheGhostofOtto1923
not rated yet Nov 16, 2018
This compares to the greatest weapon that humans possess.

"the brain represents about 2% of the body weight. Remarkably, despite its relatively small size, the brain accounts for about 20% of the oxygen and, hence, calories consumed by the body..."

-and interestingly, it grew to its present unwieldy and unsustainable size in response to demands to invent better weapons and conceive better strategies and tactics to prevail in competition over resources, in the context of tribes.

Conflict and competition drove the form and function of humans as well as their animal bretheren.
TheGhostofOtto1923
not rated yet Nov 16, 2018
The evidence is Monster wolf prince of darkness (Illuminati) wants to reap where it did not sow. It began with the peace of peace, why should it end with the wolf prince of darkness? Corned on all sides, is it worth to give in now? Matthew 4:9-11. Wolf Illuminati is a blood sucker
-Who? Nancy Pelosi?

"18 I also said to myself, "As for humans, God tests them so that they may see that they are like the animals. 19 Surely the fate of human beings is like that of the animals; the same fate awaits them both: As one dies, so dies the other. All have the same breath[c]; humans have no advantage over animals. Everything is meaningless. 20 All go to the same place; all come from dust, and to dust all return. 21 Who knows if the human spirit rises upward and if the spirit of the animal goes down into the earth?"
rrwillsj
not rated yet Nov 16, 2018
max & otto & kub missed the fact that sexual reproduction is a random scramble of conflicting possibilities. That is why we are not all clones. There have been dozens of "Big Brain" species. What sets Hominadae apart is the ability to manipulate objects and a willingness to use fire.

Our ancestors evolved modern human style bodies long before developing large brains. Even a cerebral "muscle" needs a large bone/skull to anchor onto.

And a female pelvis that can widen enough to allow exit of a "Big Headed" baby.

Yeah, Ouch! The natural selection process was bloody agony.
JaxPavan
5 / 5 (1) Nov 16, 2018
@Ojorf

I should have said flight is the easiest to hypothesize a sexual selection adaptation concisely in 1000 characters or less. . .

Suppose a Flightless creature uses flapping colorful feathers and high jumping to attract a mate in the jungle or tall grass, etc. but the high jumping and feathers do little to avoid predators until the creature can actually fly some distance.

Of course, I don't know and haven't done the research. And, I'm no expert on the proavis model, but it looks like it could also be just a reptilian version of a flying squirrel at first glance.

I disagree the sex is a problem, however. Suppose that male moose horns, besides being extremely attractive to females the larger they evolved, also allowed the male moose to teleport from place to place once the horns exceeded a certain length. Once that very competitive feature had evolved, it would only take a few generation until the females had teleportation horns too. We all have nipples.
Ojorf
1 / 5 (2) Nov 17, 2018
I think you misunderstand how sexual selection works.
The females don't just pick a feature to like, such as a long tail or bright plumage and then select males with brighter feathers or a longer tail. Quite the opposite.
Females that like a certain feature in the male are selected for because they end up having fitter offspring.
Two male birds, one with a short tail and one with a long unwieldy tail might be equally fit in the sense of finding food, building a nest, avoiding predators, fighting rivals etc. The long tailed individual will obviously need to be stronger than the short tailed one to be equally successful with his handicap.
They will both produce equally fit male offspring, but not so for female offspring. Since the long tail does not express in the females the female picking the male with the longest tail ends up having fitter, stronger female offspring that inherited her liking of long tailed males.
Ojorf
2.3 / 5 (3) Nov 17, 2018
Suppose that male moose horns, besides being extremely attractive to females the larger they evolved, also allowed the male moose to teleport from place to place once the horns exceeded a certain length. Once that very competitive feature had evolved, it would only take a few generation until the females had teleportation horns too. We all have nipples.


That is not a believable scenario. Teleporting mooses?

You need a "less fit" trait expressed in only one sex that is made up by the "more fit" advantage it confers to the other.
Then you somehow need something to happen that flips the "less fit" trait making it a survival advantage.
Then you need to transfer the advantage to the other sex.
That seems unlikely.
rrwillsj
not rated yet Nov 17, 2018
One of my favorite takes in the subject of sexual reproduction and choosing mating partners.

Is the observations of chimpanzee tribes during seasonal female estrus. The big Alpha males would get all excited and violent with one another.

And expending a lot of time and energy driving off any strange male chimps hanging around for the chance to grab a unguarded female.

During these confrontations, the females and the tribe's Beta males would sneak off into the bushes "To Get It On"!

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