The widely distributed earthworm genus Pheretima auct. containing 746 nominal species and subspecies was last reviewed in 1900 when 167 species were listed. In an attempt to increase our understanding of this group of earthworms numerical methods were used to investigate the affinities of 114 species assigned to the genus with the view to dividing it into smaller, more manageable units. A similarity matrix was obtained from a consideration of 56 characters, it was examined by the method of principal co‐ordinates analysis firstly to which a minimum spanning tree was applied, then secondly by using a five nearest neighbours' procedure. From the arrangement of the species, assemblages were detected which permitted the recognition of eight genera (one being divided into subgenera): Archipheretima, Pithemera gen. nov., Ephemitra gen. nov., Metapheretima, Planapheretima, Amynthas, Metapbhe nom. nov., Pheretima (Pheretima) and Pheretima (Parapheretima). Following research into the literature, most known species were assigned to genera and to nominal species‐groups within the genera, only a few being listed as species incertae sedis. Keys are provided to the genera and to the species and nominal species‐groups. Four Appendices are included, one contains details of a small collection of earthworms from Mount Kinabalu, Sabah, made by the Royal Society Expedition to North Borneo, with the descriptions of a new species and a subspecies. Another concerns the identity of Metaphire fordi (Michaelsen, 1934).
The nephridia were excluded from the present numerical and taxonomic investigations due to the uncertainty about their systematic significance (see Classification) and for much the same reasons that they were omitted by . The study of the nephridia would necessitate the destructive dissection of well-preserved specimens, and it was clearly undesirable to go to such extreme lengths to obtain information. Secondly, some species are represented by specimens often in poor condition due to either inadequate fixation, or previous dissections, so that information can no longer be obtained from them. Only a minority of the original descriptions include details of the nephridial system, so that it would be difficult to correlate this information.Nevertheless, variations in the nephridial system of a few species were studied for other reasons since, in the most recent classification of the Megascolecoid earthworms, Jamieson (197 la & b) attributed considerable systematic importance to the structures of the excretory systems (seeThe configuration of the taxa with the first and second vectors of the principal co-ordinates analysis as axes is shown in Fig. 6. A considerable degree of clustering is evident, which becomes clearer with the addition of the Minimum Spanning Tree (MST) with graded linkages. Four major clusters may be recognized. Two, indicated by square and triangular symbols, comprise the six species of Archipheretima and 14 species of Planapheretima respectively, which by their discreteness and the low values of the MST linkages with other clusters confirm the validities of the genera. The two other clusters, indicated by closed and open circular symbols contain the taxa Table 2 Characters used for computing coefficients of similarity 1 Mean longitude 2 Mean latitude 3 Ratio of lengths of arcs containing first five dorsal setae (v-z) : first five ventral setae (a-e) on segment vii 4 Shape of body in cross-section : circular or depressed 5 Creeping sole : present or absent 6 Segment number of anterior end of clitellum 7 Segment number of posterior end of clitellum 8 Size of spermathecal pores : large or small 9 Ratio of distance apart of posteriormost spermathecal pores : circumference of body 10 Position (furrow number) of anteriormost spermathecal pores (one 'furrow' = setal row -setal row) 1 1 Position (furrow number) of posteriormost spermathecal pores 12 Position of spermathecal pores: postsetal, intersegmental, or presetal 1 3 Main number of spermathecal pores per furrow 14 Origin of spermathecal diverticula: ectal or ental 15 Condition of spermathecal diverticula: single or multiple 16 Condition of male pores: crescentic copulatory pouches, slightly invaginated porophore, superficial porophore, superficial lacking porophore, penate simple or penate within copulatory pouches 17 Size of male pore (superficial lacking porophore only): large or small 18 Ratio of distance apart of male pores: circumference of body 19 Annular ridges associated with male pores: absent or present 20 Crescentic markings associated...
Earthworms collected from the southwestern Pacific islands of Samoa, Tonga, Fiji, Niue, and the Kermadecs on the 1980 expedition of the Soviet Research Ship Kallisto, and by other expeditions and surveys, are discussed. Nineteen species are listed: 2 are new, 12 are new records for the area, and 6 are new records for individual islands. The 2 new species are Polypheretima neglecta n. sp. and Metapheretima sergei n. sp. The littoral species of the genus Pontodrilus are reviewed and are considered to be synonymous. The type species of the genus Drawida is redescribed. Polypheretima tamarae n. sp. is described from Papua New Guinea. The origin of the earthworm fauna of the south-western Pacific is discussed and a key to the earthworms recorded from the south-western Pacific is provided.Details of the nephridial systems of 2 species of Polypheretima from Papua New Guinea are given in an appendix.
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