An international team of scientists has sequenced and assembled the genome of a venomous shrew-like insectivore called the Hispaniolan solenodon.
The Hispaniolan solenodon (Solenodon paradoxus). Image credit: Eladio Fernandez, Caribbean Nature Photography.
The solenodon is a venomous, nocturnal, burrowing, insectivorous mammal belonging to the family Solenodontidae.
As one of the only extant mammals that are venomous, the solenodon’s venomous saliva flows from modified salivary glands through grooves on their sharp incisors (‘solenodon’ derives from the Greek for ‘grooved tooth’).
The animal also has several other primitive and very unusual characteristics for a mammal — very large claws, a flexible snout with a ball-and-socket joint, and oddly positioned teats, which are on their rear.
It looks much like a shrew, however, it is considerably larger. It measures between 11 and 13 inches (28–33 cm), with the tail adding an additional 10 inches (25 cm), and weighs 600 g – 1 kg.
A black to reddish-brown pelage covers the majority of the body, with the exception of the tail, feet, nose, and tips of the ears.
The solenodon is nocturnal, and it finds shelter during the day by burrowing, or finding cover in hollowed logs, trees, or cracks in rocks.
The animal is relatively social, and up to eight individuals may inhabit the same burrow. Litter size is one or two young. The young are born in a nesting burrow. Young solenodons remain with their mother for several months, which is exceptionally long for insectivores. The solenodon’s diet includes insects and spiders found in soil and leaf litter.
The two living solenodon species are known: the Cuban solenodon (Solenodon cubanus) and the Hispaniolan solenodon (Solenodon paradoxus).
The latter species is endemic to Hispaniola, the island shared by Haiti and the Dominican Republic. It is found in forests and brush country, as well as around plantations.
The genome sequencing of this endangered species was carried out by Dr. Taras Oleksyk, a researcher wit the University of Puerto Rico at Mayagüez in Puerto Rico and Uzhhorod National University in Ukraine, and colleagues.
“While the mammalian tree of life has been heavily researched, this is the most distantly related branch to be added to the ‘genome club’,” the scientists said.
“For me, perhaps the most interesting part of this research was the challenge of delivering a de novo genome assembly that was suitable for comparative genomics, using an amount of sequencing data much smaller than in other similar projects,” said team member Dr. Kirill Grigorev, also from the University of Puerto Rico at Mayagüez.
After carrying out their assembly, the researchers had data of sufficient quality for answering many scientific questions on solenodon evolution.
With regard to conservation plans, the data supports that there was a subspecies split within the Hispaniolan solenodon at least 300,000 years ago, meaning the northern and southern subspecies — Solenodon paradoxus paradoxus and Solenodon paradoxus woodi — should be treated as two separate conservation units and may therefore require independent conservation strategies.
These data also shed light on the initial speciation event for this branch, and showed that solenodons likely diverged from other living mammals 73.6 million years ago, a remarkably ancient split that occurred while dinosaurs still roamed the Earth.
“We have confirmed the early speciation date for solenodons, weighing on the ongoing debate on whether the solenodons have indeed survived the demise of dinosaurs after the asteroid impact in the Caribbean,” Dr. Oleksyk said.
“It is difficult to determine whether the ancestors of solenodons were already in the proto-Antilles when the asteroid that killed off the dinosaurs impacted nearby, or whether their ancestors survived on the North American mainland and later dispersed onto the island,” said team member Dr. Alfred Roca, from the University of Illinois.
“Perhaps their Freddy Krueger-like claws allowed them to burrow their way to safety.”
The findings are published in the journal GigaScience.
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Kirill Grigorev et al. Innovative assembly strategy contributes to understanding the evolution and conservation genetics of the endangered Solenodon paradoxus from the island of Hispaniola. GigaScience, published online March 16, 2018; doi: 10.1093/gigascience/giy025
