To celebrate the Year of the Snake — and my 9-year anniversary with Agamemnon Fang (Python regius), who I met at the MVZ on Cal Day 2004 — here’s a sampling of snake headlines from this past year, more or less.
It doesn’t take a male and a female to make a liter of baby snakes. Zoologists have previously observed facultative parthenogenesis — that’s when females of species that usually reproduce sexually go through asexual reproduction, developing embryos without fertilization. Until now, this has only been documented in captivity. Researchers from North Carolina State University captured pregnant wild copperheads (Agkistrodon contortrix) and cottonmouths (Agkistrodon piscivorus). When these females gave birth in the lab, DNA results indicated that the chance of a male contribution was “infinitesimally small.” Asexually reproduced litters typically have a large number of failures in development such as stillborn babies, and few viable males. [Biology Letters via Nature News]
The Vibrating Skulls of Pythons
Ever wonder how snakes hear sounds without external ears? In humans, sound waves traveling through the air hit the eardrum, causing the movement of tiny bones and vibrations of tiny hair cells in our inner ear; these vibrations are translated into nerve impulses that travel to the brain. But snakes have no eardrum, and their fully formed inner ear structures are connected directly to their jawbone. Previous studies have shown that vibrations traveling through the ground — such as the footsteps of prey — cause vibrations in the jawbone, relaying a signal to the brain via that inner ear. To monitor the activity of neurons connecting the inner ear to the brain, researchers from Aarhus University in Denmark attached electrodes to the heads of ball pythons (Python regius) and played sounds above their cages. They found that the sound waves were causing enough vibration in the bone — directly through the air — for the snakes to sense it. These are then ‘heard’ by their inner ear. [Journal of Experimental Biology via ScienceNOW]
The tree-dwelling Boiga irregularis has been ravaging the ecosystem and infrastructure of Guam for nearly 70 years, annihilating 10 of the island’s 12 native bird species and costing billions of dollars in damage to electrical power systems. These destructive habits come from their incredible ability to cross gaps between trees — some as long as 2.2 meters — to catch prey in the spread-out canopies of the forest. To test the snakes’ bridging skills (video), a University of Cincinnati duo set them on perches in front of various obstacles: from vertical ascents and short drops, to horizontal gaps and sharp turns. The snakes triumphed over vertical gaps, crossing ones that were 65% wider than horizontal gaps. (One snake successfully spanned a vertical opening that was 82% of its body length.) However, they had difficulty holding their body parallel to the ground, only crossing horizontal lengths that were at most 58% of their body length. These new biometric findings could help improve gap-based barriers that the island uses to keep the snakes off power lines and away from cargo ships… and planes. [Journal of Experimental Biology via ScienceNOW]
Diseases: Good News and Bad News
Scientists may have finally found the cause of a mysterious and fatal condition called inclusion body disease (IBD), which makes snakes tie themselves up in knots, stare off into space, and waste away. A UCSF team analyzed infected snakes and found genetic material belonging to a previously unknown virus. It seems to be most closely related to a class of viruses known as arenaviruses, which are only known to infect mammals. The snake virus also contains a gene closely related to one found in the Ebola virus, which belongs to a different class called filoviruses. [mBio via National Geographic]
A new study suggests that vipers harbor the Eastern equine encephalitis virus (EEEV) through the winter. Every year, when it starts to warm up, EEEV reemerges along the eastern coast of the US, causing a devastating disease in horses, and sometimes humans. But how does the virus — which is transmitted by infected mosquitoes — survive the cold, mosquito-killing winters? A team from the University of South Florida in Tampa collected a bunch of snakes and tested their blood for signs of EEEV (such as antibodies against the virus or traces of the virus’s RNA). They found the virus in the copperhead (Agkistrodon contortrix) and the cottonmouth (Agkistrodon piscivorus). [American Journal of Tropical Medicine and Hygiene via ScienceNOW]
Pythons have always been interesting for researchers studying heart disease in people. The Burmese python (Python molurus), for example, can go for a whole year without eating. And once they swallow their prey, their heart nearly doubles in size and their metabolism speeds up fortyfold. By studying recently fed snakes, researchers from the University of Colorado, Boulder, have figured out the precise mixture of fatty acids in the blood that drives this cardiac growth. This discovery could led to drugs that help boost performance after a heart attack or stroke and, on the other hand, reduce dangerous kinds of heart growth caused by disease. [Science via ScienceNOW]
The black mamba (Dendroaspis polylepis), who can kill a human within 20 minutes, will inspire a new class of painkillers, according to researchers from the Institute of Molecular and Cellular Pharmacology in France. Among the compounds that squirt from their fangs are two proteins that can block pain in mice as effectively as morphine — and with fewer side effects. The proteins, called mambalgins, bind and inhibit molecules in the family of acid-sensing ion channels, which have been implicated in pain transmission. There’s at least one commercially available painkiller that mimics the venom of the cone snail (Conus magus). [Nature via Nature News]
Snakes are a rich source of inspiration for robot design: from climbing and pipe-inspecting snakebots to an aircraft repairing bot from Rolls-Royce. Tiny snake robots help surgeons identify diseases and perform operations — on human hearts, cancers, and diseased organs — by carrying tiny cameras, scissors, forceps, and sensors into our bodies. They help make complex surgeries faster and easier, and allow surgeons to operate with less damage to the body, which helps patients recover faster.
Georgia Tech’s all-terrain robot, Scalybot 2, replicates rectilinear locomotion (video) and can automatically change the angle of its ‘scales’ depending on the terrain or slope. Being able to efficiently crawl like snakes into tight spaces would be a huge benefit for search-and-rescue robots.
Finally, if there’s one I love as much as snakes, it’s California ground squirrels (Otospermophilus beecheyi). When confronted by predators such as Pacific rattlesnakes (Crotalus oreganus oreganus), they hold their tails upright and thrash them from side to side, notifying predators that they’re ready to dodge and flee. The tail-flagging also emits an infrared heat signal that rattlesnakes can detect, making them think twice about attacking if they’ll probably just fail. Not only does it ward off predators, but this tail-waving behavior also warns other squirrels of potential danger. A San Diego State University team sifted through hours of footage from security cameras set up around squirrel burrows, and they even deployed a robosquirrel (video) developed at UC Davis. Squirrels who waved their tails weren’t attacked, but those who didn’t, well, were. [Proceedings of the Royal Society B via ScienceNOW, CNN]