Vol. 53 - Alaska Resources Library and Information Services

They were then fed thawed juvenile gadid fish which had been collected
previously from Bristol Bay during the August 1982 cruise. The time of
feeding was noted for each crab. The crabs were frozen whole at preset
time intervals of 1.5, 4, 8, and 24 hours after being fed. Also frozen
were other red rock crabs that had not been fed and, therefore, had empty
guts (T = 0). Visual examination of the stomach contents of the
experimental crab showed that at T = 1.5 hours, fish in the gut were still
recognizable as such. Fish were still present at T = 4 and 8 hours, but
the contents were ground to a fine paste. At 24 hours the gut was empty
in some crabs, others still had a small amount of finely ground paste. At
T = 0 the crabs, indeed, had empty stomachs. Ouchterlony tests were
performed using these stomach contents to demonstrate whether or not
antigenic determinants within the gut declined over time due to digestion
processes. The fish antisera (Ab) was placed in the center well of the
slide. The fish antigen (Ag) was placed in an outer well. The time
series stomach contents were also placed in surrounding outer wells in a
manner that would easily show disappearance or retention of the precipitin
lines.
As shown in Figure 13A, the fish antisera - antigen reaction had 5
self reaction lines as expected. The two inner precipitin lines continue
through the T = 1.5 hour stomach contents and T = 4 well. One precipitin
line continues through to T = 8. There were no lines at T = 24 hours and
as expected none at T = O. The three outer precipitin lines between the
fish Ag and Ab were absent from stomachs throughout the time series. The
antigenic determinants for these 3 lines no longer existed after 1.5 hours
of digestion. There were 2 determinants that survived longer; however,
all antigenic material was gone at 24 hours. The information obtained
from this experiment correlated with the visual examination of the gut
contents. There was little, if any fish remaining in the gut at 24 hours
and no precipitin lines to indicate otherwise.
This feeding experiment was conducted with red rock crab because live
king crab were not available at Sequim. Hence any conclusions made should
be tentative until feeding experiments can be carried out with king crab
and other prey items in addition to fish. With this caveat, the
indications are still strong that the antigenic material necessary for
detection in the gut degrades with time. Moreover, some antigenic
determinants break down after a very short time in the foregut of crabs.
The loss of antigenicity correlates with the visually observed residence
time of the fish in the gut. This may be true for other soft bodied prey
species as well.
Feller et al (1979) designed an algorithm to assure that precipitin
lines observed were correctly attributed to the presence of the prey
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