Study: Island lizards have resilient stomachs

As the island-based lizards were forced to eat more plants, their stomach slowly evolved.

By Brooks Hays
An island-dwelling green lizard. Photo by Konstantinos Sagonas
An island-dwelling green lizard. Photo by Konstantinos Sagonas

ATHENS, Greece, Aug. 31 (UPI) -- New research shows island-based lizards have evolved highly versatile digestive systems, well-suited to the variability of isolated living.

In studying the guts of Balkan green lizards (Lacerta trilineata) living on Greek islands, researchers found lizards on islands have longer, more adaptive stomachs than their mainland relatives. The digestive systems of the island-based insect-eating lizards look more like plant-eating lizards, researchers in Greece say.


The adapted stomachs allow Balkan green lizards to switch more easily between plants and insects, enabling the reptiles to react more quickly to the variability of island weather (and thus, food availability).

In addition to longer stomachs and an unique gut bacteria, dissection revealed many island-based green lizards to possess cecal valves. The valves help slow digestion and create fermentation chambers, making it easier for the insect lovers to digest plant material. Where as only 19 percent of mainland green lizards had developed cecal valves, 62 percent of the island specimens possessed the valves.

"Such adaptations allow insular populations to take advantage of the limited food resources of the islands and, eventually, overcome food dearth," Konstantinos Sagonas, a researcher at the National and Kapodistrian University of Athens, explained in a press release.


Sagonas is the lead author of a new paper on the unique stomachs and eating habits of island lizards, published this week in the journal The Science of Nature.

The adaptations of the green lizards were necessitated by the island living, Sagonas and his colleagues say. As the island-based lizards were forced to eat more plants -- up to 30 percent, as opposed to 10 percent -- their stomach slowly responded.

"Energy flow in insular environments, the digestive performance of insular populations and the connections within them, provide insights into how animals are able to colonize islands and maintain viable populations."

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