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Adapted from: How a Curious Mammal Evolved Its Venom- The New York Times

By Veronique Greenwood Dec. 1, 2019
Solenodons are highly unusual, and very difficult to study
The Hispaniolan solenodon is a wondrously strange creature.
About the size of a guinea pig, it has a long, hairless snout, sharp little teeth and, to top it all off, venom-laced saliva. Highly endangered, it lives in the forests of the Dominican Republic and Haiti, and scientists have had to work hard to understand its habits and evolution. But in a paper published Tuesday, a diverse group of researchers outline the intriguing conclusions they reached about how the solenodon got its dangerous spit, after they sequenced its DNA and analyzed its venom.
It was not easy finding solenodons to study, said Nicholas Casewell, a venom expert and a co-author of the new paper. The team managed to track down two of the animals in the wild. At the National Zoological Park in the Dominican Republic, they took blood for DNA sequencing from a captive solenodon — one of the only captive specimens in the world. They compared the DNA of the soledon to those of related animals, like hedgehogs, moles and shrews, and identified substances present in the venom, including a set of molecules called kallikreins.
Kallikreins chop up other proteins, including some that help maintain blood pressure. The researchers injected mice with solenodon venom and saw that indeed, while their pulse and breathing did not change, their blood pressure dropped dangerously as soon as the venom went in. This could make prey foggy-headed and easier for the solenodon to finish off, the researchers suggest.
Another venomous mammal among the solenodon’s relatives, the northern short-tailed shrew, also has kallikreins in its venom.
"To us, it was a real surprise to find very similar proteins in the venom of the solenodon and shrews," Dr. Casewell said.
They asked whether venom might have existed in the common ancestor of moles, hedgehogs, shrews and solenodons. But if a common ancestor did have this trait, an improbably large fraction of its descendants would have had to mysteriously lose it for the modern family tree to make sense.
The researchers concluded that it is more likely that shrews and solenodons came up with the adaptation after they branched off from these other small mammals. They think the trait is likely to have evolved independently in each animal, as shrews and solenodons do not use the exact same kallikreins in their venom as shrews.
But the fact that there is an overlap in these molecules in two different animals implies that mammals have very limited options to work with when it comes to developing a venom. Kallikreins are commonly present in mammal saliva, so modifying them little by little to get something more dangerous is a plausible route for venom’s evolution.
The researchers wonder, however: Are solenodons still using their venom? The last 500 years have seen the extinction of many prey species, like lizards, birds and other vertebrates, on their home island. This ecological destruction has left behind mainly insects, which may not be affected by the venom.
Dr. Casewell and his colleagues hope that future observations of wild solenodons on the hunt may provide insight into whether its unusual venom is still useful to solenodons in their daily lives, or if it is a relic of a time, and an ecosystem, that no longer exists.
Read the article above and answer the questions 4

What is the main focus of the article?
a) The diet of the Hispaniolan solenodon
b) The extinction of prey species in the Dominican Republic
c) The evolution and characteristics of the solenodon's venom
d) The migratory patterns of the solenodon

1 Answer

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Final answer:

The article's main focus is the evolution and characteristics of the solenodon's venom, its effects, and the research concerning whether this trait evolved independently in solenodons and shrews.

Step-by-step explanation:

The main focus of the article is c) The evolution and characteristics of the solenodon's venom. The article provides an in-depth look at the unique aspects of the Hispaniolan solenodon, particularly its venom-laced saliva, which is an unusual trait among mammals. Researchers have conducted DNA sequencing and venom analysis to understand the evolution of this characteristic, leading to the discovery of kallikreins in the venom. These enzymes affect blood pressure, suggesting a method by which the solenodon's venom could incapacitate its prey. The study also explores whether venomous traits in solenodons and shrews arose independently or from a common ancestor. With the extinction of many of the solenodon’s prey species, the researchers are curious about the current usefulness of the venom in the solenodon’s hunting practices.

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