Vol. 53 - Alaska Resources Library and Information Services

Stomach fullness plotted against time after isolation proved not to
describe adequately the passage of solid material from the gut because
large amounts of liquid were still present in otherwise empty stomachs.
In fact, the volume of liquid actually increased with time after isolation
(Table 3), and otherwise empty stomachs contained enough liquid to
maintain 25 to 30% stomach fullness after 130 h. The liquid was clear to
light brown and without floc or the cloudiness indicating fine particulate
matter. Apparently the crab maintains a minimum level of digestive fluid
in its gut. To avoid confounding the determination of clearance rates by
this liquid, the volume of solid material in the stomach and the dry
weight of the stomach contents were determined.
Both the volume of solids and the dry weight of stomach contents fell
exponentially with time after isolation (Figure 4, Table 2). A twocompartmental
model described the decrease in the volume of solids and
a three-compartmental model, the loss of dry weight (Table 2). The
exponential decay curves were used later to calculate daily ration
following Elliott and Persson (1978). Dry weight of stomach contents
proved to be a better measure of stomach clearance rates than volume.
Evidence for several compartments rather than one in the exponential
decay curves comes from two sources: information concerning variation in
gut residence times of different materials (Hill, 1976; Carter and Steele,
1982) and graphical analysis of the data here. Whereas many models of
stomach clearance assume a one-compartmental exponential decay curve, it
is not reasonable to accept the implication of a one-compartmental model
that all the materials in the stomach are digested and passed out at the
same rate. Hill (1976) and Carter and Steele (1982) reported that in the
stomachs of crabs and lobsters soft tissue is lost in hours while hard
parts from bivalves and echinoderms remain for days. Thus knowing that
clearance rates do vary among different tissues, it is reasonable to
expect that a decay curve describing the passage of a mixture of materials
from the stomach would be the outcome of different clearance rates acting
on different materials initially present in different proportions. The
king crab stomachs examined for this analysis contained floc, sand, soft
tissue, shell fragments from small bivalves and gastropods, and sand
dollar tests. Finding multi-compartmental exponential models for stomach
clearance meets this reasonable expectation.
Graphical analysis indicated the number of compartments in the
specific decay curves. If the appropriate model for the exponential decay
had only one compartment, then plotting natural logarithm of the dependent
variable, e.g., the dry weight, against time would give a straight line.
For a two-compartmental model such a plot would show a straight line
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