ISSN:
1573-5192
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract Brooks, O'Grady & Glen (1985b) placed the seemingly aberrant and highly derived family Heronimidae at the base of their cladogram of the Digenea. In the absence of arguments for the composition and polarity of the putative homologous series on which their cladogram is based, it was found necessary to consider in detail almost all of their character series. In the course of my analysis I (1) argue that the oral sucker is singular to the Digenea, and that the oral sucker is not synapomorphic nor the ventral sucker symplesiomorphic for the Digenea, but that early digeneans lacked both suckers, (2) reiterate that the amphistomate condition is secondary and has arisen more than once, and that the embryology of the excretory system proves it to be secondary in all cases, (3) offer support for Cable's view that the cercarial stylet is not of single origin, and (4) restate the argument that paramphistomes, microscaphidiids, and gyliauchenids have not an oral sucker but a pharynx. Brooks, Bandoni, Macdonald & O'Grady (1989) stated that the bifurcate gut is unambiguously a synapomorph of the Digenea, on the basis of their cladistic demonstration that Rugogaster with a bifurcate gut is a sister group to the rest of the Aspidobothria, which in turn is a sister group to the digenea. Testing this in a new cladogram of the Aspidobothria constructed from Brooks et al.'s (1989) 15 characters (corrected, especially those of the ventral sucker, for which a new phylogeny is advanced), supplemented by an additional 23 characters, reveals Rugogaster as the derived form it appeared to be and aspidogastrids, with a single caecum, as sister group to the rest of the Aspidobothria. A new analysis of the characters produced an increase in homoplasy from 18% to 37%, showed 97 out of 212 characters invalid as used, these two resulting in a decrease in resolution from 82% to 32%, and resulted in changes in polarity in 20 of the 65 putative homologous series listed by Brooks et al. (1985b). The Heronimidae cannot be at the base of their cladogram as it has not three but 13 apomorphs, which is more than have the next three groups, the paramphistomiforms, echinostomatiforms and haploporiforms. Comparison of the Heronimidae with the Bivesiculidae in the light of 48 defensible plesiomorphs shows that the Bivesiculidae, which have 39 of the 48 characters, are more plesiomorphic than the Heronimidae, which have only 23. In conclusion, what remains of the data-base is insufficient to support their cladogram and classification. Better data from the flukes themselves are necessary for a sound cladistic analysis.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00010255
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