Triturus viridescens is a U. S. newt which spends the first three to
six months of its life as a water larva, then—in some parts of the
country at least—comes out to take up residence on land. On land the
newts are bright red in color, are known as “red efts.”
During this phase they are immature and cannot reproduce. After three
or four years, they go back to the water, slough off the red skin of
adolescence, assume the olive-green garb of adults, acquire the keeled
tail of an aquatic animal, and tackle the business of parenthood.
Question: What impels them, after so long a time on land, to go back to
the water? Scientists of an older generation would have answered,
“Instinct.” Biologists Edwin Eustace Reinke and Claude
Simpson Chadwick of Vanderbilt University and the Highlands
Biological Laboratory nabbed some North Carolina specimens of T.
viridescens in the immature red eft stage and implanted bits of adult
pituitary gland in their muscles. Within six days the newts went into
the water and assumed the adult body color and tail shape. Thus it
seemed that the pituitary provided not only the necessary physiological
changes for aquatic life but also the “water drive” or
impulse to seek water.In mammals the pituitary, that master gland, secretes a half-dozen or so
hormones which control or influence
growth, body heat, blood pressure, milk production, maternal behavior,
etc. Sometimes the pituitary achieves its ends by stimulating other
glands, such as the sex glands or thyroids, to produce hormones of
their own.To make sure that neither the sex glands nor thyroids are involved in
the newts' water drive, Reinke & Chadwick removed the sex glands
from some red efts, the thyroids from others, both the sex glands and
thyroids from still others, and then repeated the pituitary treatment.These creatures, the investigators reported last week in the Journal of
Experimental Zoology, went back to water just the same, though some
took as long as eight days and made many hesitant passes at the water
before getting in for good. It looked as if only a pituitary could
drive a newt to water.
