The Scientist - USA (2020-11)

11.2020 | THE SCIENTIST 49

ISTOCK.COM, KIRISA99; THOMAS MARTIN

OUTTA MY WAY: The front set of legs of centipedes such as Scolopendra

subspinipes have evolved into venom-injecting pincers.

CELL & MOLECULAR BIOLOGY

Receptor Deflector

THE PAPER

S. Yang et al., “Target switch of centipede toxins for antagonistic

switch,” Sci Adv, 6:eabb5734, 2020.

While it’s handy to be able to neutralize prey or would-be

predators with a bite or sting, being a venomous animal can be

dangerous. Usually critters avoid the effects of their own venom

“by keeping it in glands where it doesn’t go into the bloodstream

and doesn’t affect them,” explains evolutionary biologist

Kevin Arbuckle of Swansea University in the UK. But because

accidents happen, it’s also advantageous to be able to survive

exposure to one’s own toxic concoction—often by lacking the

receptors the venom’s components bind to.

The centipede Scolopendra subspinipes both kills prey with

its venom and uses it to temporarily stun conspecifics during

fights for dominance. Ren Lai of the Kunming Institute of

Zoology in China writes in an email to The Scientist that he and

his colleagues wanted to understand why prey and conspecifics

react differently.

In several of the centipede’s prey species, including mice, a

venom component known as spooky toxin binds to potassium

channels, including one called shaker, wreaking havoc on the

nerves that control breathing and heartbeat. Lai’s team found

the shaker channel in S. subspinipes cells carries a single amino

acid change that protects the species from the worst effects

of the venom. Injecting the centipedes with venom from

other S. subspinipes, Lai and his colleagues confirmed that the

arthropods were only temporarily immobilized; they recovered

within 10 minutes. Cell culture experiments revealed that

spooky toxin inhibited the shal channel, which affects both

neurons and the vascular system and most likely explains the

centipedes’ immobilization.

The experiments, says Arbuckle, who was not involved in the

study, are “a really cool integration” of molecular-level work on

venom and observations of the different purposes for which it’s used.

—Shawna Williams

NO NEST, NO PROBLEM: Long-lived tropical bird species such as the

indigo flycatcher (Eumyias indigo) reduce their reproduction rate during

a drought and up their chances of survival, a study finds.

ECOLOGY & ENVIRONMENT

Barren Birds

THE PAPER

T.E. Martin, J.C. Mouton, “Longer-lived tropical songbirds reduce

breeding activity as they buffer impacts of drought,” Nat Clim

Change, doi:10.1038/s41558-020-0864-3, 2020.

Thomas Martin was studying parenting behavior among wild birds

in Venezuela when a drought hit in 2008. In one species, the gray-

breasted wood wren (Henicorhina leucophrys), the number of active

nests in his team’s study area declined from 65 in 2007 to just 7

during the drought, the University of Montana wildlife biologist says.

Reproduction comes at a cost, because animals must expend

energy producing and caring for their young, so Martin wondered

what effect this temporary drop in reproduction might have on the

adult birds’ survival rates. To find out, he set up another experiment

in 2009, this one in the forests of Borneo. With then–graduate

student James Mouton and their field assistants, Martin caught and

banded birds, and began to record nest locations and bird sightings.

Seven years later, a drought hit.

It wasn’t as severe as the one in Venezuela in 2008, where

there was a more than 50 percent average reduction in nests across

18 species, and Martin suspects that’s why the effects he and his

team saw in Borneo weren’t as extreme. Still, the 20 bird species

studied in Borneo reduced the number of nests in which they laid

eggs by an average of 36 percent compared with the year before.

The level of reduction varied among species, with long-lived birds—

those with average lifespans of about 10 or more years—reducing

their reproduction the most. And in contrast to past studies that

indicated that birds’ survival drops during droughts, survival rates

increased in the species that were most inclined to hold off on

having offspring.

“The contrast between long-lived and short-lived species in how

they cope with a stressful environment is striking,” writes Rosemary

Grant, an emeritus biologist at Princeton University who was not

involved in the study, in an email to The Scientist. The research, she

says, “provides a good example of the value of long-term studies.”

—Shawna Williams