Morphology of the Feeding Apparatus of Cancer novaezelandiae in Relation to Diet and Predatory Behavior
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1990-10
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University of Hawaii Press
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Abstract
Morphology of the mouthparts, gastric mill, and chelae of the
New Zealand cancer crab, Cancer novaezelandiae Jacquinot, 1853, was investigated
in relation to dietary composition and predatory behavior. Mouthparts
and gastric mill were typical of those of other large, predatory brachyurans, with
similar structure for male and female, small (60-70 mm) and large (120-130 mm
carapace width) crabs. The third maxilliped had large crista dentata, and the
inner margin of the mandible was rounded, with a sharp, cutting edge. The large,
robust chelae were homeochelous with respect to structure and dental pattern.
A large diastema was present and both chela exhibited high mechanical advantage
(0.36 and 0.37 for left and right chela, respectively). Relative growth of the
propodus was positively allometric, which remained constant throughout crab
growth. Morphological features of the feeding apparatus suggested adaptations
for macerating coarse, particulate material. This was supported by foregut
analysis showing a predominance of sessile and slow-moving macroinvertebrates
in the diet. Bivalve and gastropod molluscs followed by crustaceans dominated
the diet; fish, sponges, coelenterates, and plant matter occurred less frequently.
Little variation in dietary composition was evident with crab sex, size, or season.
Cancer novaezelandiae adopted five distinct techniques to open bivalve shells and
three techniques to open gastropod shells. These include direct, umbone and
posterior crushing, umbone splitting, posterior chipping, and aperture breakage
and spire removal. The success of these techniques was dependent upon crab
size and prey size and shape. Large crabs were able to use direct crushing over
a wider size range of prey than smaller crabs. The structural and behavioral
adaptations permit C. novaezelandiae to specialize on mollusc prey and may
explain its migrations into areas dominated by molluscan species.
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Creswell PD, Marsden ID. 1990. Morphology of the feeding apparatus of Cancer novaezelandiae in relation to diet and predatory behavior. Pac Sci 44(4): 384-400.
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