Lumbricillus tuba Stephenson, 1911

Klinth, Marten J., Rota, Emilia & Erseus, Christer, 2017, Taxonomy of North European Lumbricillus (Clitellata, Enchytraeidae), ZooKeys 703, pp. 15-96 : 38-39

Lumbricillus tuba Stephenson, 1911 Fig. 16

Lumbricillus tuba Stephenson, 1911: pp. 42-46, figs 5 a–b, pl. I, figs 6-8; Nielsen and Christensen 1959: p. 105, fig. 131; Erséus et al. 2010; Klinth et al. 2017.

Type material.

Typus amissus (Nomenclatura Oligochaetologica). Type locality: Firth of Clyde, Millport, Island of Cumbrae, United Kingdom ( Stephenson 1911). We did not designate a neotype as we do not have material from the type locality.

Material examined.

ZMBN 107916 (CE22614), one mature specimen from Norway. For information on specimen collection locality and GenBank accession number see Appendix 1. Note that this specimen is the only sexually mature available for this study, but additional (immature) worms were studied genetically by Klinth et al. (2017).

Description.

White to grey worm. Length (fixed worm) more than 4.8 mm (amputated specimen), first 15 segments 2.0 mm long, width at clitellum 0.39 mm. More than 39 segments. Chaetae slightly sigmoid (Fig. 16A). Dorsal bundles with 2-3 chaetae anterior to clitellum, 2-3 chaetae in postclitellar segments. Ventral bundles with 3-4 chaetae anterior to clitellum, 2-3 chaetae posteriorly. The worm’s longest measured chaeta 48 µm long, about 3 µm wide. Clitellum extending over XII– 1/2XIII. Head pore not observed. Epidermis with transverse rows of gland cells.

Coelomocytes numerous, 20 µm long, spindle-shaped, oval, round, granulated. Paired pharyngeal glands present in IV, V and VI (Fig. 16B). Dorsal vessel originating in XII. Nephridia not observed. Brain longer than wide, further shape unclear.

Male genitalia paired (Fig. 16D). Testes originating in XI, extending forwards into IX, with testis sacs forming regular club-shaped lobes. Sperm funnels in XI, 120 µm long, 105 µm wide, making them slightly longer than wide, funnels tapering towards vasa deferentia. Most of vasa irregularly coiled in XII, 10 µm wide. Penial bulbs round, 85 µm in diameter. Ovaries in XII. Two mature eggs present.

Spermathecae (Fig. 16C) in V, club-shaped, with distinct ampulla. Ectal duct as long as ampulla, abruptly widening into oval ampulla. Sperm circularly arranged in ampulla. Spermathecae 120 µm long, 85µm wide at widest part of ampulla. Gland cells surrounding ectal pore, forming compact mass, whole glandular body 75 µm in diameter at its widest part. Three midventral subneural glands in XIII– XV, 85µm, 90 µm and 85 µm long, respectively.

Geographical distribution including BOLD data.

Genetically identified from Norway and Sweden. Also described from Denmark and the United Kingdom. BIN-number: BOLD:ACQ1913.

Remarks.

Our specimen matches the original description by Stephenson (1911) well in most characters, including the shape of the spermathecae and the proportions of the sperm funnels. However, its body size was smaller and the chaetae per bundle slightly fewer than in the original description.

Lumbricillus tuba is genetically most closely related to the L. pagenstecheri group (including L. viridis ), but it is morphologically most similar to L. scandicus sp. n. described below.