Experiments on Gill Reduction in Neotonous Triturus viridescens

In certain regions neotonous individuals of Triturus viridescens are found in the same ponds with metamorphosed ones. Their gills persist after the body fin has been lost and the sex organs are well developed. 1 The object of these experiments was to find out whether such gills could be affected by environmental changes. If this occurred it would indicate that the hereditary background of these newts was different from that of those that lose their gills early. 2 Attempts to reduce the gills were made (1) by forced residence in a dry environment, (2) by implants of anterior pituitary lobe taken from gill-less adults from another region and (3) by implants of thyroid gland from the same source.

Gilled newts from Woods Hole, 6 to 10 cm. in length, and typical gill-less adults from South Hadley collected in October and November were used. Experiments were carried on through the winter and spring. Among 500 Woods Hole newts, 75% had gills on each side containing circulating blood. Their sex organs were partially or completely developed. The thyroids of 6 gilled newts suggested a state of rather low activity. 3 A slightly less inactive condition obtained in thyroids of gill-less individuals from Woods Hole. On the other hand, the thyroids of South Hadley adults appeared active (compare adult Ambystoma opacum, Uhlenhuth 3 ).

On October 14, 1930, 2 lots of Woods Hole newts with gills averaging 0.13 cm. in length were divided into 4 groups according to size. Twenty were kept in jars cushioned with moss occasionally sprinkled with water. Twenty others were kept in jars of water. Ten aquatic adults (South Hadley) were kept in moss-bedded jars and 10 in water. All were kept under the same conditions.