| dc.description.abstract | Internal structures of the proventriculus of adult tiger beetles were
examined to determine their function and taxonomic and phylogenetic value.
The overall appearance of the proventriculus suggested an intricate filter
designed to permit the flow of nutrient fluids into the midgut while retaining
particulate food; this corroborates earlier hypotheses of tiger beetle feeding
behaviour. The intricate proventricular structure indicates that regurgitation of
midgut liquids does not occur during regular feeding. S.E.M. and light
microscope observations revealed eight longitudinal internal folds, four minor
and four major plicae, lined with ctenidia. The minor plicae become apodemes
posteriorly and displayed anteriorly directed ctenidia which were shown to vary
among cicindelid subgenera. The ctenidia of the major plicae varied in length
independently of the plical height at both the anterior and posterior regions of
the organ. Slopes which were calculated from these measurements describe the
inner proventricular structure between the anterior and posterior ends of the
proventriculus and were shown to differ among cicindelid subgenera and
species groups. Advanced taxa displayed flatter proventricular slopes. The
proventricular slope data were compared to habitat types of seventeen species.
Among classified species of the maritima group, proventricular slopes reflected
traditional phylogenetic relationships rather than habitat distinctiveness.
Significant differences of proventricular slopes were shown among species
groups having different ancestral habitats. A histological examination of the
foregut of Cicindela tranquebarica Herbst third instar larva revealed that the
proventriculus is absent at this stage. The overall structure of the proventriculus
of the primitive tiger beetle Omus audouini Reiche displayed the close
phylogenetic relationship of this genus with the genus Cicindela although some
variations were noted. By comparison, in adults of the carabid Carabus
nemoralis Muller, "socketed setae" and cuticular ctenidia covered the intima of
this organ. Based on the comparative morphology of the proventriculus,
members of Omus and Cicindela were concluded to demonstrate a phylogenetic
relationship, with Carabus nemoralis more distantly related. | |
