Lumbricillus pagenstecheri (Ratzel, 1869), a species complex

Klinth, Marten J., Rota, Emilia & Erseus, Christer, 2017, Taxonomy of North European Lumbricillus (Clitellata, Enchytraeidae), ZooKeys 703, pp. 15-96 : 34-35

Lumbricillus pagenstecheri (Ratzel, 1869), a species complex

Enchytraeus pagenstecheri Ratzel, 1869: pp. 587-588, pl. XLII, figs 2, 13, 20b & 21.

Pachydrilus pagenstecheri ; Vejdovsky 1877: p. 298; Ditlevsen 1904: pp. 433-434, fig. 29, pl. XVIII, fig. 6; Knöllner 1935: p. 436; Černosvitov 1937: p. 292.

Lumbricillus pagenstecheri ; Ude 1901: p. 9, pl. I, fig. 14; Southern 1909: p. 153; Stephenson 1925: pp. 1315-1316; von Bülow 1957: pp. 77-78, pl. XXV, figs 1-7; Nielsen and Christensen 1959: pp. 104-105, figs 117-120; Erséus 1976: pp. 9-11, fig. 8.

Lumbricillus henkingi Ude, 1901: pp. 9-10, pl. II, figs 15-18; Stephenson 1925: p. 1315.

Lumbricillus ritteri Eisen, 1904: pp. 84-86, figs 53-54, pl. XIII, figs 5-9; Nielsen and Christensen 1959: p. 97; Erséus 1976: pp. 9-10, fig. 12.

Lumbricillus aegialites Stephenson, 1922: pp. 1126-1130, figs 2-3; Stephenson 1924: p. 211; Stephenson 1925: p. 1314.

Lumbricillus necrophagus Stephenson, 1922: pp. 1130-1133, figs 4-5.

Lumbricillus georgiensis Tynen, 1969: pp. 390-391, figs 1-3.

Type material.

Typus amissus (Nomenclatura Oligochaetologica). Type locality: The original material was collected in Rhine River near Karlsruhe, and in ponds around Heidelberg, Germany ( Ratzel 1869), but none of these places has yet been specifically designated as the type locality. We did not designate a neotype as we do not have material from any of the original localities, nor do we know which one, if any, of our cryptic species that represent the true nominate species.

Remarks.

The molecular studies by Klinth et al. (2017) supported the delimitation of four different species with the morphology of L. pagenstecheri , here denoted as cryptic species A–D. Particularly the morphology of the spermathecae characterizes this group. There are two groups of gland cells, one creating the typical mass of glands surrounding the ectal pore, as seen in the other species of Lumbricillus , and the other group composed of numerous, rather long, gland cells covering the ectal duct. These two groups of gland cells can be difficult to distinguish from each other, depending on the orientation of the mounted specimens, but they create the impression of a very narrow duct followed by a distinct, almost spherical, thin-walled ampulla. While there seems to be some morphological differences between the four species in this study, such as size and number of chaetae, there are too few sampled specimens to verify that these characters do not overlap.

Lumbricillus pagenstecheri was originally described by Ratzel (1869) from the Rhine River in Germany and has later been re-described by Nielsen and Christensen (1959) as well as others and today includes five synonymized species (listed above). Such synonymies may need reappraisal as there are some differences between the original descriptions concerning size, number of segments and number of chaetae and there is a possibility that some of the synonymized species are present in our material. Moreover, about thirteen described species from the Northwestern Pacific and eight from the Northeastern Pacific have a morphology similar to that of L. pagenstecheri (Timm 2005), and a more extensive phylogenetic study focused on this part of the genus will be necessary, to resolve the taxonomy of this complex group.

For this study, we chose to present the morphological measurements only for our cryptic species A, which is the only one with a sufficient sample size, and provide a comparison of some characters with the other three cryptic species in Table 2. In general, species B and D where the largest, species D possessed fewer chaetae per bundle than the others, and for species C we unfortunately had no fully mature specimens. Full information on collection localities and accession numbers of all four species are given in Appendix 1.