Mary Juhn

Developmental Analysis in Plumage. III. Field Functions in the Breast Tracts

T HE degree of correspondence between vane-halves of the individual feather varies over a remarkable range. Certain feathers of all tracts are approximately symmetrical with respect to obvious characteristics, such as pigmentation patterns, the length of barbs, the distribution of barbs on the shaft, the distribution of barbules, etc. Other feathers from the same tract show asymmetry in some or all of these elements of structure or configurations of pattern. In some instances, e.g., the primaries, the asymmetry in the vane-halves becomes extreme and is evident in marked differences of pigmentation configurations, spacing of barbs, and mass of individual barbs. In other feathers, e.g., saddle feathers, the asymmetry is of much lesser apparent degree but is nevertheless easily recognizable in one or another respect in most feathers of the tract. These general relations have, of course, long been known and in some instances have received considerable attention from the morphological point of view (e.g., Chandler, 1916). The distribution of differing symmetry types within plumage tracts has been treated quantitatively by Landauer (1930). Working with the spangled (apical) pattern of the Silver Spangled Hamburg, Landauer established general relations of reversed asymmetry on the two sides of the body. In at least one instance (the wing coverts of the male) he recorded a definite sequence of asymmetry types. Lillie and Juhn (1932) considered the asymmetry of the individual feather in terms of physiological principles, i.e., in terms of

Individual Feather Succession in the Hybrid Capon.

The plumage of the F-1 males resulting from a cross in either direction between Barred Rocks and Brown Leghorns in general resembles that of the Barred Rock though the pattern is not strictly identical. Spaced among the barred plumage are feathers, the so-called exceptional feathers, which may be completely identical with those of the Brown Leghorn male, or, while exhibiting both barred and leghorn characteristics in general, yet show a number of traits foreign to either parent. The occurrence of these exceptional feathers is practically entirely confined to the plumage regions in which barbules are restricted to the vicinity of the shaft and to the basal feather sections, the saddle, hackle, head and minor coverts. The greater number of exceptional feathers possess a barred tip and leghorn base; the barred region may occupy one vane-half, or the margin only of the feather, in which case the transition takes place within individual barbs, and yet other variations. Feathers similar to these have been described in hybrids resulting from a cross between Plymouth Rocks and Orloffs by Serebrovsky, 1 by Hertwig and Rittershaus 2 from a cross between Barred Rocks and Goldlack, and from a cross between Plymouth Rocks and Faver-olles by Kuhn. 3 Serebrovsky attributes the origin of the exceptional feathers to the loss of one sex-chromosome carrying the factors for barring in development; Hertwig and Rittershaus to the frequent loss of the part of the X-chromosome containing the factor which inhibits black and white regions of barred feathers. Both Kuhn and Hertwig and Rittershaus state that exceptional follicles always produce exceptional feathers identical in pattern with the exceptional feathers plucked.

Growth Rates of Successive Feathers from Single Follicles in the Juvenile Brown Leghorn.

The juvenile plumages of the Brown Leghorn of both sexes pass through a series of changes in pigmentation during successive regenerations. These changes are particularly notable in the feathers which are present at hatching, or emerge shortly after hatching. In the wings and tails, for example, the first feathers to appear are stippled or mottled. The second generation of these feathers shows marked changes towards the adult pattern. In pigmentation, third generation feathers are practically identical with homologous feathers of the adult. It has been shown previously from this laboratory that there is a direct relation between the concentration of female hormone or thyroxin required for reaction and rate of growth of feathers. (Juhn and Gustavson, 1 Juhn, Faulkner and Gustavson, 2 Lillie and Juhn 3 ). There is also a definite range of growth rates characteristic of the feather tracts, and of individual feathers within the tract (Juhn, Faulkner and Gustavson, 1931). These growth relations known to exist in the adult suggest that the juvenile pattern types and changes in these types may be correlated with changes in rates of feather growth during successive juvenile regenerations. In order to test this assumption, we have determined the rates of growth of feathers from a number of tracts in Brown Leghorn chicks. Measurements of length of feathers were begun as soon as possible after hatching, or appearance of feathers, and continued over 2 (in some cases 3) successive regenerations. In all cases which we have studied the rate of growth of the first feather from a given follicle is lowest; second and in many instances third generation feathers grow at increasing rates. The changes in rates of growth of successive feathers from a single follicle are well illustrated by the main tail feathers.

Pattern Analysis in Plumage. III. Action of Thyroxin in High Concentrations

The sequence of response of the components of the definitive feather to increasing thyroxin concentrations—blanching of barbs, barbule formation, and pigment deposition—and the manner of estimating barb growth in the germ by observation of the order of appearance of pigment following injection of thyroxin have been established by Lillie and Juhn. 1 An examination of definitive feathers subjected to heavy thyroxin dosages (10 mg., single injection) during development shows that both barb frequency and barb lengths are markedly altered. Barb frequency increases to a level around twice the barb frequency of a normal feather; a sudden drop then occurs to a level below that characteristic of barb frequency for the same region of the control feather. Barb length decreases following injection of thyroxin, then gradually returns to normal or possibly greater than normal length. These relations are shown in the accompanying graph. The curves are for single longitudinal vane-halves of modified and control neck feathers. Distances from origin of rhachis are given in centimeters on the horizontal axis. Figures on the left ordinate refer to barb frequency, i. e., the number of barbs per millimeter rhachis length. Figures on the right ordinate apply to barb lengths.

Feathers as Indicators of Concentration of Female Hormone in the Blood.

In the first observations made in this laboratory on the induction of feathering in capons and cocks subsequent to injections of chemically prepared hormone during the period of feather regeneration, regional variations in the degree of plumage responses became evident. It was noted that feathers having a more rapid growth rate required definitely higher concentrations of hormone for the female reaction than feathers having a slower growth rate. 1 The growth rates of feathers in various parts of the body have now been accurately measured, and constant regional differences have been established. The birds used for these experiments were brown leghorn fowls, and in this breed the capon is similar in plumage to the cock. In both cock and capon, the growth rate of the feathers is greater in the breast than in the saddle or back, and even greater in the posterior than in the anterior region of the breast. The ratio between the most rapidly and the most slowly growing feathers when measured in growth in length per day is approximately 2:1. In the hen differences in growth rate in various parts of the body are slight, and the general rate for all is intermediate between the maximum and minimum rates of the cock. The threshold concentrations of hormone required for the reaction are closely correlated with this observed difference in growth rate. Feathers formed on a capon receiving regular effective daily injections of female hormone are completely female in character; if, however, the injections are restricted to short periods of time, then bars or patches of female color are laid down on an otherwise male type of feather. One single injection will, if sufficiently large to produce the threshold concentration, be recorded by the feather.

Spur Growth and Differentiation in the Adult Thiouracil-Treated Fowl

HAS been shown by Astwood, Bissel, and Hughes (i944) that thiouracil T via its interruption of the secretory activity of the thyroid will cause a marked retardation of growth in the young chick. When thiouracil was fed as 0.5 per cent from within the first week of age onward, the muscles became weak and the joints became hypermobile. The head furnishings and the spurs failed to develop, and the down of the body was not replaced by the juvenile plumage as is normal. The authors noted, though,

Plumage Sequence in a Case of Hemilateral Asymmetry in Male Hybrid Fowl

by an individual becomes of special interest when it is manifest in a system subject to continued regeneration; for, if first encountered at an early age, it may be seen that, if the asymmetry is static, identical pattern succeeds identical pattern, whether or not it fluctuates in degree with each changing developmental level of the organism or even if it may perhaps become completely obliterated in the later life of the originally asymmetric individual. The observation in this laboratory of a young cockerel showing a distinct hemilateral asymmetry in the distribution of the pigment patterns of its feathering suggested promise for study in such respects, since the plumage, as is well known, represents something of an embryonic system, persisting during life and giving rise to series of successive feather generations. The appearance of the first juvenile plumage and that of its next successor stage in this bird have been briefly described in an abstract (Juhn, 1942); here the material will be dealt with more fully and with special reference to the patterns developed in the successive feathers proliferated by follicles of strictly comparable opposite position in the body.

The relation of the plumage-tract gradients to the serial localization of feather pigments in a hybrid cock.

acters and plumage sex characters by injection of human placental hormone in fowls. Jour. Exper. Zo61., 56:31-61. ---. 1932. The response of a vestigial Milllerian duct to the female hormone and the persistence of such rudiments in the male fowl. Anat. Rec., 52:299-311. KUMMERL6WE, H., and FROB6SE, H. 1930. Ein linksseitiges Oviduktrudiment (Miillerscher Gang) bei einem erwachsenen Starmannchen (Sturnus vulgaris L.). Zeitschr. f. mikr.-anat. Forsch., 22:414-26. LANDAUER, WALTER. 1940. Studies on the Creeper fowl. XIII. The effect of selenium and the asymmetry of selenium-induced malformations. Jour. Exper. Zo6l., 83:431-43. LILLIE, FRANK R. 1931. Bilateral gynandromorphism and lateral hemihypertrophy in birds.

Pattern Analysis in Plumage. II. Methods of Definitive Feather Analysis

The correspondence of events in the germ and definitive feather pattern characteristics is implicit in the relations which Lillie and Juhn have shown to exist in the collar during the reaction of barbs at all levels to high concentrations of thyroxin and female hormone. From this point of view measurable elements of pattern are of direct developmental and physiological significance. Definitive pattern relations are also of direct importance in other respects, as in the quantitative formulation of symmetry relations. We report here methods which have been developed to give the desired data. The characteristics of the definitive feather which can be measured are distances between barbs on rhachis, lengths of barbs, and lengths of pattern elements within the limits of definition as barb or rhachis segment. Barbule lengths and distances between barbules may also be measured in certain instances. (a) Mounting the feather. In order to obtain the desired measurements on barb length and barb frequency with precision and reasonable rapidity it is necessary that the feather be permanently mounted with reference to simplest possible axes, i. e., with barbs at right angles to rhachis. The rhachis of the feather is first set in paraffine, applied hot, on the glazed surface of heavy bristol board. The barbs are then brushed out until they lie approximately at right angles to the rhachis. The bristol board is now clamped down on a base movable in the line of and exactly parallel to the rhachis. Above this sliding frame and at right angles to its line of motion is a guide bar.