Neoteny with Goitre in Triturus helveticus By JM - Journal of Cell ...

Neoteny with Goitre in Triturus helveticus 

By J. M. DODD AND H. G. CALLAN 

(From the Department of Natural History, The University, St. Andrews) 

With 2 plates (figs, i and 2) 

SUMMARY 

A population of newts from a pond near Crail, Fife, was found to contain neotenic 

and goitrous specimens of Triturus helveticus in 1951 and 1952 but not in 1953 and 

1954. This is a unique record of goitre among amphibians. 

The thyroid glands of normal adult and neotenic non-goitrous T. helveticus are 

paired spheroidal or ellipsoidal bodies whose longest dimension varies between 300 

and 700 fi. They consist of a few large follicles. The thyroid glands of the goitrous 

neotenic specimens may be as much as 4 mm. long. They are extremely hyperplastic 

and hyperaemic and for the most part consist of follicles smaller than those characteristic 

of normal newt thyroids. These goitrous thyroids produce major displacement 

of other structures in the throat region but do not invade other tissues. 

It is suggested that the goitres result from the exposure of overwintering newt larvae 

to the 'brassica factor' carried to the pond in the faeces of rabbits feeding on turnips 

and kale in neighbouring fields. 

CONTENTS 

PAGE 

I N T R O D U C T I O N . . . . . . . . . . . . . I Z I 

M A T E R I A L . . . . . . . . . . . . . 1 2 2 

M O R P H O L O G I C A L A N D H I S T O L O G I C A L D E S C R I P T I O N O F T H E T H Y R O I D G L A N D S . . - 1 2 3 

S T A T U S O F T H E G O I T R E S . . . . . . . . . . . 1 2 5 

T H E N E W T P O P U L A T I O N . . . . . . . . . . . 1 2 5 

D I S C U S S I O N . . . . . . . . . . . . . 1 2 6 

R E F E R E N C E S . . . . . . . . . . . . . 1 2 8 

INTRODUCTION 

'nr^HE phenomenon of neoteny is well known in urodeles, but, so far as we 

J. are aware, none of the many records in the literature mentions an accompanying 

goitre. Duchosal and Junet (1926) studied a single neotenic specimen 

of Triturus ('Triton') alpestris and reported that the thyroid gland did not 

differ in histological appearance from that of a normal specimen. Kuhn (1925) 

studied the thyroid glands of a single neotenic specimen of Triturus cristatus: 

he found the glands to be normal in size, though consisting of more numerous, 

smaller follicles than is usually the case in normal specimens. Hartwig and 

Rotmann (1940), in an extensive study of a partially neotenic population of 

'Triton taeniatus' (Triturus vulgaris), state that the neotenic specimens which 

they examined had thyroid glands of normal size but showing some histological 

signs of low activity. They also point out, however, that the histological 

[Quarterly Journal of Microscopical Science, Vol. 96, part 1, pp. 121-128, March 1955.]

122 Dodd and Callan—Neoteny with Goitre in Triturus helveticus 

appearance of normal newt thyroids varies considerably through the year and 

that there is no sharp distinction between neotenic and normal specimens as 

regards the histological appearance of these glands. Hartwig and Rotmann 

furthermore give a comprehensive review of the findings of previous workers 

on urodele neoteny: the same subject has also been reviewed by Wolterstorff 

and Freytag (1951) and by Lynn and Wachowski (1951): nowhere has goitrous 

enlargement of the gland been encountered. 

Not only have goitres never been reported from urodeles in nature: experimental 

work testing various goitrogens has shown that both urodeles and 

anurans are highly resistant to the goitrogenic activity of these substances. 

Joel, D'Angelo, and Charipper (1949) have pointed out that the changes in 

amphibian thyroids induced by various goitrogens are both qualitatively and 

quantitatively less marked than those which occur in birds and mammals as a 

result of similar treatment. Adams (1946) kept adult specimens of Triturus 

viridescens in strong solutions of thiourea for 86 days and found only slight 

hyperplasia. In view of these findings the occurrence in nature of neotenic 

newts with accompanying goitre is of particular interest. 

MATERIAL 

In a routine collection of newts from a pond near Crail, Fife, on 19 May 1951, 

two neotenic specimens of T. helveticus Razoumowsky were noticed. One was 

a female, length 71 cm., the other a male, length 6-5 cm. Both specimens were 

in full breeding dress, yet with persistent larval gills and larval head shape. 

Both specimens died within 3 days of capture, probably owing to their having 

been kept in damp moss instead of water. Neither of these newts showed evident 

external signs of goitre and histological examination was not attempted. 

In a further collection of newts from the same pond on 14 May 1952, two 

more neotenic specimens of T. helveticus were obtained. One animal, length 

6-7 cm., with well-developed male secondary sexual characters, showed a pronounced 

bilobed pink swelling in the throat region lying below the operculum 

and extending beyond it posteriorly. A photograph of this animal (specimen A) 

is shown in fig. 1, A. The swelling was diagnosed as a goitre and subsequent 

histological examination confirmed this diagnosis. The other neotenic specimen 

from this collection, a male, length 5-2 cm. (specimen B), had no goitre. 

Subsequently three further neotenic goitrous specimens (C, D, and E) of 

T. helveticus were obtained from the same pond on 11 July 1952. All three 

animals were females, their respective overall lengths being 7-0, 7-5, and 

7-0 cm. Photographs of specimens D and E are shown in fig. 1, B-D. 

During 1953 the pond was visited on numerous occasions and several hun- 

FIG. 1 (plate). A, specimen A, showing goitre, persistent gills, and male secondary sexual 

characters. 

B, specimen D, profile view. 

c, specimen D, ventral view showing asymmetral goitre. 

D, specimen E, ventral view showing smaller bilateral goitre.

mm. 

• • / * ' 

I mm. B 

D

Dodd and Callan—Neoteny with Goitre in Triturus helveticus 123 

dred newts were examined. Throughout the year 1953 and up to the present 

time in 1954, neither neotenic nor goitrous newts have been found. 

All the labelled neotenic specimens were fixed in Bouin's fluid and the 

entire lower jaw of each was serially sectioned to the level of the posterior 

margin of the thyroid glands. The histology of the glands is described in the 

next section. Owing to an unfortunate accident the pituitary glands of these 

animals were not subjected to histological examination. 

The pond from which these newts were obtained lies in a deep pear-shaped 

pit in heavy soil. It is approximately 100 feet long by 50 feet wide at the widest 

point. The pit was originally excavated as a stone quarry but the sides, steeply 

sloping for the most part, are now covered with soil and heavily overgrown 

with vegetation. No figures are available as to depth, though this is evidently 

considerable and may well reach 15 or more feet. The water surface, which 

shows marked fluctuation in level from one season to another, lies some 25 

feet below the level of the surrounding agricultural land. 

A thriving rabbit colony inhabits the sides of the pit and feeds in the surrounding 

fields. These fields are all under cultivation, turnips and kale being 

grown as part of the normal rotation. It is suggested later that this may have 

some bearing on the occurrence of the goitre. 

MORPHOLOGICAL AND HISTOLOGICAL DESCRIPTION.OF THE THYROID GLANDS 

Normal and neotenic non-goitrous specimens 

The thyroid glands of normal adult newts are paired structures lying immediately 

anterior to the arterial arches and lateral to the genio-hyoideus 

muscles. They are spheroidal or ellipsoidal bodies, the longest dimension 

varying between 300 and 700/z. They consist of a few large follicles and have 

no distinct capsule. The follicular epithelium varies through the year from 

squamous to cubical, and the degree of vacuolation of the colloid also varies. 

Specimen B is neotenic but non-goitrous. Its thyroid glands (fig. 2, A) lie 

within the size range of those of normal newts of similar size (600 by 560/n), 

but they show signs of low activity. The central section of a complete series 

shows seven large follicles full of eosinophil colloid, which is poorly vacuolated. 

The follicular epithelium is low and the cell boundaries are difficult 

to make out. 

Neotenic goitrous newts 

The goitres described here have many features in common though they 

vary considerably in size, the largest extending from mid-eye region to the 

level of the heart and causing great distension of the entire throat. All are 

markedly hyperaemic, the hyperaemia being readily visible through the operculum, 

whose epidermis, though semi-transparent, is flecked with yellow 

pigment. The goitres result in major displacement of structures in the throat 

region, though there is no invasion of other tissues such as has been found in 

fish thyroid gland tumours. The goitres are not encapsulated, but their


boundaries are well marked and distinct. The follicular epithelium is not 

folded: mitotic figures are not common. The colloid is variable in staining 

reaction in different parts of the gland: vacuoles are small and few in number. 

Specimen A (figs, i, A and 2, B) showed the largest goitre in the series. The 

goitre is symmetrically bilobed, each lobe measuring approximately 4 by 

3-5 mm. With the exception of the genio-hyoideus muscles and the skeletal 

structures it occupies the entire throat region. The follicles are more or less 

uniform in size and are smaller than those found in a normal newt thyroid. 

Cytological details cannot be described since the specimen was fixed after 

death. 

Specimen C also showed a bilobed goitre, the dimensions of each lobe being 

approximately 2 by 2-3 mm. The follicular epithelium varies from squamous 

to high columnar: there are few large follicles with low epithelium and abundant 

poorly vacuolated colloid, and many small follicles with high columnar 

epithelium and little or no colloid. The colloid varies in staining reaction. In 

the large follicles it takes eosin and Heidenhain's haematoxylin, whereas in all 

the small follicles it takes Heidenhain's haematoxylin exclusively (fig. 2, D). 

A few cellular inclusions are present in the colloid. The large follicles are 

irregular in shape and elongated in diverse planes: such follicles are reminiscent 

of the normal thyroid gland, having low epithelium, indistinct cell 

boundaries, and colloid with few vacuoles. 

Specimen D (fig. 1, B, c; fig. 2, c, E, F). The thyroid gland on the right-hand 

side of this specimen measures 4 by 4-5 mm. and is much larger than that of 

the left-hand side (1-4 by i-6 mm.), though both are goitrous. The larger 

gland contains many small follicles, each with high columnar epithelium and 

very small lumen: some regions are non-follicular. There are no cell inclusions 

in the colloid. The follicles of the smaller gland are larger, the follicular 

epithelium varying between cubical and squamous. A large number of small 

peripheral vacuoles are present in the colloid. 

Specimen E (fig. 1, D; fig. 2, G). The goitre in this specimen is smaller than 

FIG. 2 (plate), A, specimen B, T.S. lower jaw showing thyroid glands of normal size. Bouin 

fixation; iron haematoxylin and orange G / erythrosin. 

B, specimen A, T.S. lower jaw showing massive goitre. The area at top centre consists of 

the genio-hyoideus muscles. Bouin fixation after death; iron haematoxylin and eosin. The 

operculum of this specimen was dissected away before fixation. 

C, specimen D, T.S. lower jaw showing asymmetrical goitre. Bouin fixation; iron 

haematoxylin and orange G / erythrosin. 

D, specimen C, T.S. of part of lower jaw showing goitre. Bouin fixation; iron haematoxylin 

and eosin. Two regions can be differentiated, one in which the follicular epithelia are low and 

the colloid eosinophil, the other with higher epithelia and the colloid stained with haematoxylin. 

E, specimen D, T.S. of non-follicular and microfollicular regions of goitre. Bouin fixation; 

iron haematoxylin and orange G / erythrosin. 

F, specimen D, T.S. of single follicle. Bouin fixation; iron haematoxylin and orange 

G / erythrosin. 

G, specimen E, T.S. of single follicle showing low epithelium and cellular inclusions in the 

colloid. Some of these included cells appear to be in the process of division. Bouin fixation; 

Mallory's triple stain.


those of the preceding specimens (approximate dimensions of each lobe, 17 by 

i-8 mm.): it is symmetrically bilobed. Each gland has a relatively normal 

looking medio-ventral region with large follicles having eosinophil colloid and 

cubical to squamous epithelium. There are few non-follicular areas. Many of 

the follicles have colloid in which there are large spheroidal vacuolated cells 

with nuclei similar to those of the cells of the follicular epithelium itself. 

STATUS OF THE GOITRES 

As already mentioned in the introduction, previous authors have described 

few or no histological signs of abnormality in the thyroid glands of neotenic 

newts. The thyroid glands described in the present paper, on the other hand, 

are evidently extremely hyperplastic and they appear to have been under the 

influence of an abnormally high level of circulating thyroid-stimulating hormone. 

Though there is no invasion of foreign tissue, the glands are so massive 

as to have caused gross displacement of neighbouring structures in the lower 

jaw. Marine and Lenhart (1910) have argued at length as to the status of socalled 

thyroidal carcinomata encountered in trout: in spite of the fact that the 

trout tumours invade bone, muscle, and other tissues, these authors have concluded 

that the tumours merely constitute an extreme example of endemic 

goitre and that they are not truly cancerous. The newt goitres resemble closely 

in histological appearance the spontaneous thyroidal growths described by 

Gorbman and Gordon (1951) in Xiphophorus montezumae, and we consider 

that they should in all probability be similarly classed as thyroidal tumours 

of a benign nature. 

THE NEWT POPULATION 

Although we can give no accurate idea of the size of the newt population in 

the pond at Crail, this certainly numbers several hundred adults and may well 

run into thousands. The population is mixed and includes both T. helveticus 

and T. vulgaris. Collections made in March or April include only 10 per cent, 

or less of vulgaris, but the vulgaris component of the population increases 

during the spring and by June the two species appear to be almost equally 

common. Towards the end of the breeding season the relative abundance of 

vulgaris declines. T. vulgaris in most localities in Britain leaves the water at 

the end of the breeding season and hibernates terrestrially: clearly the habits 

of vulgaris in this pond are those normal for the species. 

T. helveticus is considered to be more aquatic in its habits than T. vulgaris 

(compare Smith, 1951, p. 65). Many, though not all, of the helveticus inhabiting 

the Crail pond overwinter in the water and we have collected them as late 

as November in large numbers and in full breeding dress. Collections in 

March, however, although consisting for the most part of fully aquatic specimens 

in good condition, include also a small proportion of specimens which 

have lately returned to the water, these being recognizable by the rough 

texture of their skins. Overwintering larvae are common and in spring collec-


tions these show marked variation in size, some being presumably in their first 

and some in their second year of life. 

The neotenic and goitrous newts which we have collected all belong to the 

species T. helveticus. Such specimens form not more than i or 2 per cent, of 

the total number of helveticus which we have examined. Since most of our 

large-scale collections have been made in April or May we have handled far 

fewer vulgaris from this pond. This may account for our failure to find neotenic 

and goitrous specimens of vulgaris: alternatively such animals may not 

be present in this population. 

DISCUSSION 

Many theories have been put forward in attempts to account for the occurrence 

of neoteny in urodele Amphibia. We do not propose to review the subject 

exhaustively in the present paper since extensive surveys have already 

been made by Hartwig and Rotmann (1940) and by Lynn and Wachowski 

(1951). Most theories postulate dysfunction of the thyroid and/or pituitary 

glands, due to intrinsic or extrinsic agents. 

No student of urodele neoteny has succeeded in providing histological evidence 

of pituitary dysfunction, but several other lines of evidence converge 

to implicate the pituitary in this phenomenon. In Anura the important 

role played by the pituitary in metamorphosis has been known for many 

years (Allen, 1916). The experiments of Reineke and Chadwick (1939) 

on T. viridescens have demonstrated that the urge to enter the water habitat 

is dependent on a hormone produced by the anterior lobe of the pituitary. 

Blount (1939) caused the metamorphosis of the normally neotenic Amblystoma 

mexicanum by implantation of pituitary rudiments from the normally metamorphosing 

A. tigrinum. As a consequence of this and later work (Blount and 

Blount, 1947), it has been claimed that two types of thyroid-stimulating 

hormone are produced by the pituitary, one being responsible for the production 

and storage of thyroid secretion, the other concerned with its release. 

Blount and Blount suggest that in neotenic forms the releasing hormone is 

absent, but the evidence is as yet by no means conclusive. The literature on 

neotenic newts contains frequent references to specimens which are partial 

albinos. Partially albino newts are rare: so are neotenic newts. Clearly there 

is a correlation between these two conditions (Smith, 1951) and the pituitary 

gland may conceivably be the common factor. 

Above all, the pituitary gland's connexion with neoteny has been frequently 

postulated on account of the controlling influence which it is known to exert 

over the thyroid; and knowledge of the implication of the thyroid itself in 

amphibian metamorphosis dates from the classical experiments of Gudernatsch 

(1913) and Allen (1916) on Rana spp. and of Jensen (1916) and Huxley 

and Hogben (1922) on Amblystoma. The present observations substantiate 

this connexion: neotenic newts are rare; goitres have only been observed in 

neotenic specimens. These two phenomena are clearly correlated with one 

another.


Any attempt to account for neoteny in newts is faced with the problem of 

the coexistence in the same pond of neotenic and normal specimens. All 

recorded cases are similar in this respect. Several authors have consequently 

been led to postulate a genetic origin of neoteny. In all experiments where 

neotenic newts have given rise to offspring, including a successful mating of 

a virgin neotenic female with a neotenic male T. vulgaris, the offspring have 

metamorphosed as rapidly as have normal control larvae. Although there may 

be a genetic component determining a tendency to neoteny, this will be most 

difficult to demonstrate owing to the well-known acceleration of metamorphosis 

which regularly attends the raising of newt larvae in captivity. 

Several authors have attempted to correlate the occurrence of neoteny with 

peculiarities of habitat, but Hartwig and Rotmann, in reviewing the literature 

on this subject, were unable to find any significant factors common to ponds 

with neotenic newt populations. Nevertheless there are two distinct indications 

that habitat peculiarities may act as causative factors. Zeller (1899) found 

neotenic specimens of three different species, T. vulgaris, T. alpestris, and 

T. cristatus in one and the same quarry pond, while Smith (1950) has described 

two ponds containing neotenic newts together with giant anuran tadpoles. 

Low iodine concentration in the environment is one of the best authenticated 

causes of goitre. In the present instance, however, although no iodine 

determinations have been made for the water of the pond in question, it seems 

unlikely that lack of iodine could be the cause since the pond lies within two 

miles of the sea and in a district where extensive use is made of sea-weeds as 

fertilizers. Furthermore the iodine content of Crail drinking water, which is 

taken from a nearby reservoir, is given as 5 meg. per litre by Murray and 

others (1948). This is the second highest iodine concentration recorded in 

determinations for 64 Scottish localities. 

We are led to postulate that the thyroid goitres here described were produced 

by the action of a naturally occurring goitrogen, the so-called 'brassica 

factor' (see review by Lever, 1951). The goitrogenic action of a diet of cabbage 

on rabbits was first demonstrated by Chesney and others (1928) and the 

active substance isolated and synthesized by Astwood and others (1949). The 

latter authors identified the 'brassica factor' as L-5-vinyl-2-thiob'xazolidone. 

Our evidence in favour of this hypothesis is based on four considerations. 

First, the land surrounding the Crail pond is extensively cultivated: the crop 

rotation practised includes yellow turnip and kale, and these plants were 

grown in fields bordering the pond in 1951 and 1952 but not in 1949, 1950, 

or 1953. Neotenic newts were collected in 1951, neotenic and goitrous newts 

in 1952, but neither in 1953 or 1954. Secondly, rabbits which have their 

burrows in the slopes leading down to the pond feed in the surrounding fields. 

Rabbit faeces accumulate in large quantities on the slopes and rainwater 

carries faeces and extract of faeces into the pond by drainage. It might reasonably 

be expected that this drainage water should contain the 'brassica factor' 

at times when the rabbits are feeding on turnips and kale. Thirdly, the 

majority of the larvae and adults of T. helveticus overwinter in the water of the


Crail pond and hence are more exposed to any goitrogens which may be 

present than are newts which habitually overwinter on land. Fourthly, although 

adult amphibians are known to be highly resistant to goitrogens, we 

do not know how larval and metamorphosing animals are likely to react. From 

unpublished work on metamorphosing Xenopus larvae in which extensive 

goitres have resulted from thyroidectomy (possibly due to the hyperplasia of 

supernumerary follicles) it would appear that the thyroid is in a particularly 

sensitive state at the time of metamorphosis. Should this be true also of newts, 

the overwintering helveticus larvae might well be exposed to the postulated 

goitrogen at this critical time. 

We have no experimental evidence in support of the above hypothesis. 

Crude extracts of seeds of Brassica spp. have unfortunately proved highly 

toxic to both larval and adult newts and in further work we must test the 

activity of the purified 'brassica factor'. In our hands 0-05 per cent, thiourea 

and coi per cent. 2-thiouracil have failed to prevent metamorphosis and have 

also failed to produce goitres in newt larvae taken from the Crail pond. 

This study forms part of a research programme in comparative endocrinology 

which is supported by a grant from the Nuffield Foundation. Our 

thanks are also due to Mr. D. R. R. Burt and Mr. M. D. B. Burt who introduced 

us to the pond at Crail and who captured the first neotenic specimens. 

REFERENCES 

ADAMS, A. E., 1946. Anat. Rec, 94, 532. 

ALLEN, B. M., 1916. Science, 44, 755. 

ASTWOOD, E. B., GREER, M. A., and ETTLINGER, M. G., 1949. Ibid., 109, 631. 

BLOUNT, R. F., 1939. Proc. Soc. exp. Biol. N.Y., 40, 212. 

BLOUNT, R. F., and BLOUNT, I. H., 1947. Anat. Rec, 97, 380. 

CHESNEY, A. M., CLAWSON, T. A., and WEBSTER, B., 1928. Johns Hopkins Hosp. Bull., 43, 261. 

DUCHOSAL, P., and JUNET, W., 1926. Arch. Anat. Strasbourg, 6, 397. 

GORBMAN, A., and GORDON, M., 1951. Cancer Res., 11, 184. 

GUDERNATSCH, J. F., 1913. Arch. EntwMech. Org., 35, 457. 

HARTWIG, H., and ROTMANN, E., 1940. Ibid., 140, :95. 

HUXLEY, J. S., and HOGBEN, L. T., 1922. Proc. Roy. Soc, B, 93, 36. 

JENSEN, C. O., 1916. Medd. VetHojsk. Serumlab. Kbh., 44. 

JOEL, T., D'Angelo, S. A., and CHARIPPER, H. A., 1949. J. exp. Zool., no, 19. 

KUHN, O., 1925. Biol. Zbl., 45, 483. 

LEVER, J., 1951. Experientia, 7, 201. 

LYNN, W. G., and WACHOWSKI, H. E., 1951. Quart. Rev. Biol., 36, 123. 

MARINE, D., and LENHART, C. H., 1910. J. exp. Med., 12, 311. 

MURRAY, M. M., RYLE, J. A., SIMPSON, B. W., and WILSON, D. C, 1948. Medical Research 

Council Memorandum No. 18. London (H.M. Stationery Office). 

REINEKE, E. E., and CHADWICK, C. S., 1939. Proc. Soc. exp. Biol. N.Y., 40, 691. 

SMITH, M., 1950. Brit. J. Herpetol., 1, 91. 

1951- The British amphibians and reptiles. London (Collins). 

WOLTERSTORFF, W., and FREYTAG, G. E., 1951. Abh. Ber. Naturkd. Vorgesch. Magdeburg, 8, 

137- 

ZELLER, E., 1899. Jh. Ver. vaterl. Naturk. in Wurttemb., 55, 23.

Neoteny with Goitre in Triturus helveticus By JM - Journal of Cell ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?