On the position of the digenean family Heronimidae: an inquiry into a cladistic classification of the Digenea

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. 82 J.C. Pearson

Utility of the D1 domain of nuclear 28S rRNA for phylogenetic inference in the Digenea

“…The former cluster was weakly supported (52-56% of bootstrap replicates) but is consistent with one of two alternative hypotheses proposed by Pearson (1992). Based on the presence of a terminal pharynx and oesophageal bulb Pearson (1992) argued that the gyliauchenids were more closely related to the paramphistomids than either was to the lepocreadiids.…”

“…Phylogeny above the family level in the Digenea, however, is arguably the most controversial area in helminth systematics (Pearson, 1972(Pearson, , 1992Clark, 1974;Cable, 1974;Brooks et al, 1985, Brooks, 1989Gibson, 1987). A key problem is the paucity and widespread evolutionary convergence of characters from morphology and life-cycles.…”

Molecules and Morphology in Phylogenetic Studies of the Hemiuroidea (Digenea: Trematoda: Platyhelminthes

“…This leads us to believe that both kinds of data are of value in inferring relationships among the Digenea. Pearson (1992) might have been overly pessimistic about the phylogenetic value of those morphological and life cycle characters identified to date within the Digenea. However, it is evident that only partial resolution of the taxa analyzed here can be achieved with the present morphological data.…”

“…For the purposes of this study, we have retained family status for these taxa but otherwise regard the Hemiuroidea as containing the taxa listed by Gibson and Bray (1979), with the addition of the Didymozoidae. Pearson (1992), in a review of work by Brooks et al (1985Brooks et al ( , 1989, concluded that morphological homoplasy was extensive and that too few unambiguous synapomorphies had been identified to permit a cladistic treatment of the Digenea. Here we present the first molecular phylogeny for the Hemiuroidea, test for congruence between morphological and molecular data, and explore the evolution of some morphological characters.…”

The phylogeny of the Lepocreadioidea (Platyhelminthes, Digenea) inferred from nuclear and mitochondrial genes: Implications for their systematics and evolution

“…Paragyliauchen is always monophyletic in all analyses and never directly related to the non-amphistomatous clade, despite the fact that it does not exhibit extreme amphistomy, in that the ventral sucker is placed non-terminally with the testes largely posterior to it (Yamaguti 1934, Machida 1984. Cable and Hunninen (1942), Cable (1956) and Yamaguti (1971) all considered the gyliauchenids close to the lepocreadiids and the latter included them within the Lepocreadiidae, whereas other authors have considered gyliauchenids closer to paramphistomes or microscaphidiids, due to the lack of an oral sucker (Ozaki 1937a, b;Pearson 1992). Much was made by Manter (1940) and Cable and Hunninen (1942) of the shared presence of the lymphatic (or paranephridial) system in gyliauchenids and lepocreadiids.…”