Myology and Serology of the Avian Family Fringillidae: A Taxonomic Study

by William B. Stallcup

Table 2.—Percentage values obtained from analyses of precipitin reactions. Numerals represent relative amounts of reaction between antigens and antisera. Homologous reactions are arbitrarily valued as 100 per cent, and heterologous reactions are expressed accordingly. Comparisons are meaningful only if made within each horizontal row of values.

Antigens	ANTISERA
Passer domesticus	75	74	73	66	81	72	...	81
Estrilda amandava	100	88	75	...	79	72	53	...
Poephila guttata	95	100	77	67	87	81	...	...
Molothrus ater	66	54	69	65	86	75	69	75
Piranga rubra	...	...	100	...	...	...	...	89
Richmondena cardinalis	75	80	91	100	98	65	88	91
Spiza americana	65	68	...	71	100	64	67	80
Carpodacus purpureus	70	71	71	61	89	93	53	70
Spinus tristis	72	74	73	60	89	100	60	...
Junco hyemalis	64	56	74	65	87	68	100	...
Zonotrichia querula	65	71	...	67	89	75	...	100

Antigens were diluted with 0.9 per cent phosphate-buffered saline solution. Tests were run in standard Kolmer test-tube racks, each test consisting of 12 tubes. Each dilution was made on the basis of the known protein concentration of the antigen. The first tube contained an initial dilution of 1 part protein in 250 parts saline and each successive tube contained a protein dilution one-half the concentration of the preceding tube, ranging up to 1:512,000. Saline controls, antiserum controls, and antigen controls were maintained with each test to determine the turbidities inherent in these solutions. These control-turbidities were deducted from the total turbidity developed in each reaction-tube, the resultant turbidity then being considered as that which was caused by the interaction of antigens and antibodies. The turbidities were allowed to develop over a 24-hour period. In the early stages of this investigation the reactions were allowed to take place at 2°C. in order to inhibit bacterial growth. Later tests were carried out at room temperatures, and bacterial growth was prevented by the addition to each tube of 'Merthiolate' in a final dilution of 1:10,000.

Experimental Data

Corrected values for the turbidities obtained were plotted with the turbidity values on the ordinate and the antigen dilutions on the abscissa. The homologous reaction was the standard of reference for all other test reactions with the same antiserum. By summing the plotted turbidity readings, numerical values are obtained which are indices serving to characterize the curves. Such values were converted to percentage values, that of the homologous reaction being considered 100 per cent. These values, plus the curves, provide the data by means of which the proteins of the birds may be compared. Plots representative of the precipitin curves are presented in Figs.[ 10] to[ 21]. For convenience each plot represents only several of the 10 curves obtained with each antiserum.

A summary of the serological relationships of the birds involved in the precipitin tests is presented in Table[ 2], in which percentage values are presented. Since the techniques involved in testing were greatly improved as the investigation proceeded, the summary is based solely on those tests run in the later stages of the investigation. For reasons which will become apparent in later discussion, it should be emphasized that in Table[ 2] comparisons may be made only within each horizontal row of values.