A University of Tennessee professor participated in a study on a breed of Japanese snake with the rare trait of borrowing poison from other animals. The study, with professors from the United States and Japan, will be published in next week’s issue of the Proceeds of the National Academy of Sciences.
UT psychology professor Gordon Burghardt studies the Japanese Tiger Snake, or Rhabdophis tigrinus. In 1991, Burghardt attended a conference where he met professor Akira Mori of Kyoto University in Kyoto, Japan, one of the leading research universities in the country and Asia. “He (Mori) said they had some snakes (in Japan) that had some interesting defensive behavior,” Burghardt said.
Burghardt, who specializes in animal behavioral psychology, began studying the reptile’s curious behavior and soon joined a study with Mori, Alan H. Savitzky and Deborah A. Hutchison of Old Dominion University in Norfolk, Va., among others. Now the group has published its findings. The report in the Proceeds, titled “Dietary sequestration of defensive steroids in nuchal glands of the Asian snake Rhabdophis tigrinus,” examined a series of hypotheses regarding the tiger snake.
Scientists have noticed that, when attacked, the snake arches its neck and thrusts it toward its attacker. Most snakes try to protect their neck, a part of their body that most prey strike first. Upon further inspection, scientists found a set of glands along the snake’s neck. These glands release a toxin when the snake is attacked. Though unclear if the toxins are deadly, they have a nasty taste and ward off predators. The researchers noticed that tiger snakes eat toads, which are highly toxic animals that few other animals can survive eating. The researchers then hypothesized that the toxins from toads were stored in the snake’s neck glands — nuchal glands — and used for its own defense.
“Many invertebrates sequester dietary toxins for use in their own defense, including such classic cases as milkweed insects and sea slugs,” the report said. But it is rare for vertebrates (animals with backbones) to borrow toxins for their own defense, and the process is seen mainly in poison dart frogs and a variety of New Guinea birds that eat so many poisonous insects their bodies and/or feathers become saturated in toxins. However, these animals do not contain glands that secrete toxins, a trait seen only in the tiger snake. Toads contain a special toxin known as bufadienolides. It is bufadienolides that the snake secretes from its glands.
For the first part of the study, the researchers took four sets of unfed baby snakes from their mothers. Two sets came from mothers with toxins in their glands. The other two came from mothers without toxins. The babies were given controlled diets — some ate fish, others non-toxic frogs and others toads. The study found that babies from mothers with toxins inherited toxins for 8.5 days, and then the toxins disappeared. The clutches that ate toads maintained the toxins. In the second part of the study, the scientists took snakes from toad-free islands in Japan. These snakes lacked toxins in their glands. They also did not arch and thrust their necks like those snakes from islands with toads. However, when fed toads, they borrowed the toxins and began arching and thrusting their necks. “These results further support the sequestration hypothesis and demonstrate that R. tigrinus have not lost the ability to sequester toxins,” the report said. The evidence indicated that the tiger snakes derived their nuchal gland toxins from toads. Burghardt plans to travel to Japan in the summer of 2008 to continue his research.
UT psychology professor Gordon Burghardt studies the Japanese Tiger Snake, or Rhabdophis tigrinus. In 1991, Burghardt attended a conference where he met professor Akira Mori of Kyoto University in Kyoto, Japan, one of the leading research universities in the country and Asia. “He (Mori) said they had some snakes (in Japan) that had some interesting defensive behavior,” Burghardt said.
Burghardt, who specializes in animal behavioral psychology, began studying the reptile’s curious behavior and soon joined a study with Mori, Alan H. Savitzky and Deborah A. Hutchison of Old Dominion University in Norfolk, Va., among others. Now the group has published its findings. The report in the Proceeds, titled “Dietary sequestration of defensive steroids in nuchal glands of the Asian snake Rhabdophis tigrinus,” examined a series of hypotheses regarding the tiger snake.
Scientists have noticed that, when attacked, the snake arches its neck and thrusts it toward its attacker. Most snakes try to protect their neck, a part of their body that most prey strike first. Upon further inspection, scientists found a set of glands along the snake’s neck. These glands release a toxin when the snake is attacked. Though unclear if the toxins are deadly, they have a nasty taste and ward off predators. The researchers noticed that tiger snakes eat toads, which are highly toxic animals that few other animals can survive eating. The researchers then hypothesized that the toxins from toads were stored in the snake’s neck glands — nuchal glands — and used for its own defense.
“Many invertebrates sequester dietary toxins for use in their own defense, including such classic cases as milkweed insects and sea slugs,” the report said. But it is rare for vertebrates (animals with backbones) to borrow toxins for their own defense, and the process is seen mainly in poison dart frogs and a variety of New Guinea birds that eat so many poisonous insects their bodies and/or feathers become saturated in toxins. However, these animals do not contain glands that secrete toxins, a trait seen only in the tiger snake. Toads contain a special toxin known as bufadienolides. It is bufadienolides that the snake secretes from its glands.
For the first part of the study, the researchers took four sets of unfed baby snakes from their mothers. Two sets came from mothers with toxins in their glands. The other two came from mothers without toxins. The babies were given controlled diets — some ate fish, others non-toxic frogs and others toads. The study found that babies from mothers with toxins inherited toxins for 8.5 days, and then the toxins disappeared. The clutches that ate toads maintained the toxins. In the second part of the study, the scientists took snakes from toad-free islands in Japan. These snakes lacked toxins in their glands. They also did not arch and thrust their necks like those snakes from islands with toads. However, when fed toads, they borrowed the toxins and began arching and thrusting their necks. “These results further support the sequestration hypothesis and demonstrate that R. tigrinus have not lost the ability to sequester toxins,” the report said. The evidence indicated that the tiger snakes derived their nuchal gland toxins from toads. Burghardt plans to travel to Japan in the summer of 2008 to continue his research.
