Lumbricillus helgolandicus (Michaelsen, 1927)

Klinth, Marten J., Rota, Emilia & Erseus, Christer, 2017, Taxonomy of North European Lumbricillus (Clitellata, Enchytraeidae), ZooKeys 703, pp. 15-96 : 41-43

Lumbricillus helgolandicus (Michaelsen, 1927) Fig. 18

Pachydrilus helgolandicus Michaelsen, 1927: p. 12, fig. 11; Michaelsen 1934: pp. 135-141, fig. 1.

Type material.

ZMH V5786 Zoologisches Museum Hamburg ( Michaelsen 1927), syntype, now designated as lectotype. Type locality: Helgoland beach.

Description of lectotype.

White worm. Length (fixed) 13 mm, 41 segments; first 15 segments 4.9 mm long, width at clitellum 1.1 mm. Prostomium hemispherical. Chaetae straight to slightly sigmoid (Fig. 18A). Dorsal bundles with 3-5, chaetae anterior to clitellum, 2-3 chaetae in postclitellar segments. Ventral bundles with 3-5 chaetae anterior to clitellum, 2-3 chaetae posteriorly. The worm’s longest measured chaetae 70 µm long and about 7.5 µm wide. Clitellum extending over XII.

Coelomocytes numerous, about 25 µm long, round or oval. Paired pharyngeal glands present in IV, V and VI; each pair converging dorsally, with large ventral lobes. Nephridia observed in XX, XXVI–XXVII, and possibly VIII–X, about 120-130 µm long, anteseptale consisting of funnel only, duct originating posteroventrally.

Male genitalia paired (Fig. 18C). Testes originating in XI, extending forwards into X, and possibly IX, with testis sacs forming regular club-shaped lobes. Sperm funnels in XI, about 685 µm long, 205 µm wide making them about 3.5 times longer than wide. Funnels cylindrical, gradually tapering towards vasa deferentia. Vasa with irregular coils around ovaries in XII, about 17 µm wide. Penial bulbs round 230 µm in diameter. Several large oocytes but no mature eggs present.

Spermathecae (Fig. 18B) in V, club-shaped, with ampulla distinctly set apart from ectal duct. Ampulla sub-spherical, thin-walled, entally possibly communicating with oesophagus. Sperm in ampulla, aggregated into irregular mass or in circle embedded in wall of ampulla. Spermathecae 290-350 µm long, 180-190 µm wide at widest part of ampulla. Gland cells surrounding ectal pore, forming large compact mass, 235-285 µm in diameter at its widest part. Four midventral subneural glands in XIV–XVII, 225 µm, 205 µm, 145 µm and 115 µm long, respectively.

Geographical distribution.

Originally described from Germany.

Remarks.

We have mounted and re-examined the only remaining syntype of L. helgolandicus from the Zoological Museum in Hamburg and found the worm to correspond well to the descriptions of L. helgolandicus by Michaelsen (1927, 1934) and no doubt to represent the attached species name. However, we found some discrepancies with the published measurements of the sperm funnels (also discussed above). As the slide of the mounted specimen is of good quality and since this is the only remaining syntype of the species we designate ZMH V5786 as the lectotype of L. helgolandicus .

Based on morphology, L. helgolandicus is similar to L. scandicus and is probably closely related to this species. In the DNA-based phylogeny, L. scandicus is placed close to the lineatus group (Fig. 1), and it is likely that L. helgolandicus phylogenetically belongs there too. However, for convenience of morphological identification, both taxa are referred to the paraphyletic " tuba " group.