Dichogastrini Jamieson, 1971

Dichogastrini Jamieson, 1971 and Acanthodrilinae Vejdovsky, 1884 .

The Dichogastrini were defined by presence of a single stomate meronephridium median to astomate micromeronephridia on each side in caudal segments, in the absence of posterior enteronephry ( Jamieson 1971a). It has, however, repeatedly been questioned (e.g., Jamieson 1978, 1981; Dyne 1984) that dichogastrins with acanthodrilin male pores (here represented by Dichogaster ) are monophyletic with those with megascolecin pores (e.g., Digaster ).

The present analyses relegate “acanthodrilin dichogastrins” ( Dichogaster and Neodiplotrema ) to the Acanthodrilinae and “megascolecin dichogastrins” (albeit represented only by Digaster and Didymogaster ) to the Megascolecinae s.l. in combined and separate analyses for both mtDNA and 28S with overall good support (e.g., BS support of 77% in the combined ML tree, Fig. 4 View FIG ).

The Nearctic Diplocardia longiseta appears to lie within this “acanthodrilin” clade (83% BS, Fig. 3 View FIG ) but the only available data (the 28S) are not sufficient for further resolution and more taxa are required. Diplocardia Garman, 1888 has been shown by James (1990) to be closely similar in morphology to Diplotrema . The available 12S data support the argument ( Jamieson 1995) that Rhododrilus glandifera , in the Wet Tropics of Queensland, is locally derived from a precursor with the acanthodrilin arrangement of male pores (probably Diplotrema with which it has a 99% BS value in Fig. 3 View FIG ) though this requires confirmation from analysis of larger numbers of sequences. R. glandifera thus appears to deserve a subgeneric rank in Diplotrema or generic rank separately from Rhododrilus , the type-locality of which is in New Zealand.

All trees from combined data endorse recognition of the Acanthodrilinae for worms with acanthodrilin male pores, including acanthodrilin Dichogastrini ( Dichogaster ) (though there is lack of resolution for 28S, Fig. 2) but not those ocnerodriles ( Eukerria ) with acanthodrilin or other male terminalia. The ocnerodriles (albeit represented only by Eukerria ) are phylogenetically distinct in the present study and are well-defined morphologically.