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Vol. 53 - Alaska Resources Library and Information Services

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eing tested rather than to cross reactions. The algorithm is by design<br />

relatively conservative. Because only one or two reaction lines were<br />

occurring, any antisera that had a cross reaction of 2 or more with king<br />

crab (see Table 26, column 17) would automatically be eliminated from<br />

consideration as a prey item. Such antisera included Spisula sp, hermit<br />

crab, Balanus, <strong>and</strong> gadid fish - food items which visual examination of gut<br />

contents had demonstrated as present in the gut. An example of the<br />

application of Feller's algorithm is given in Figure 14.<br />

In any given antigen there may be antigenic determinants that will<br />

survive longer when subjected to digestive processes as evidenced by the 2<br />

out of 5 remaining precipitin lines from the king crab that fed on the<br />

sabellid polychaete. The few precipitin lines that did occur in king crab<br />

stomachs were related to strong antigenic determinants. How long they<br />

remain is determined by the digestive processes of a particular organism<br />

<strong>and</strong> the composition of the antigenic determinant.<br />

Because of rapid digestion in the guts of crab, it was apparent that<br />

Feller's algorithm of counting the number of precipitin lines <strong>and</strong><br />

subtracting cross reactions was not going to suffice for this study.<br />

Because there was information to be obtained from the precipitin<br />

reactions, Feller's algorithm was replaced with a different approach that<br />

experimentally determined the type of precipitin reaction. According to<br />

Roitt (1971), there are three basic patterns (Figure 13b) of precipitation<br />

that can be obtained in Ouchterlony tests:<br />

(a) The REACTION OF IDENTITY - this occurs between identical antigenic<br />

determinants, causing the precipitin lines to fuse giving<br />

a continuous arc.<br />

(b) The REACTION OF NONIDENTITY - this occurs where two antigens do not<br />

contain any common antigenic determinants, causing the precipitin<br />

lines to form independently <strong>and</strong> cross without any interaction.<br />

(c) The REACTION OF PARTIAL IDENTITY - this occurs where partially<br />

related antigens have one common determinant giving a continuous<br />

line of identity. An extra determinant in one of the antigens gives<br />

a line of nonidentity causing a spur to form.<br />

To separate positive predator-prey interactions from potential cross<br />

reactions Feller's algorithm was replaced with more immunoassay tests<br />

using lines of identity <strong>and</strong> nonidentity. The procedure for all the crab<br />

stomachs was first to test the stomach contents against all the antisera.<br />

Any antisera that showed a positive reaction with contents was retested<br />

235

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