Lumbricillus viridis Stephenson, 1911

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

Lumbricillus viridis Stephenson, 1911 Fig. 15

Lumbricillus viridis Stephenson, 1911: pp. 46-50, figs 6 a–b & 7 a–c; Nielsen and Christensen 1959: pp. 103-104, fig. 116; Klinth et al. 2017.

Pachydrilus orthochaetus Delphy, 1921: pp. 64-82, figs 29-41.

Type material.

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

Material examined.

ZMBN 107933 (CE12037), ZMBN 107934 (CE12038), ZMBN 107935 (CE12039) & ZMBN 107938 (CE23255), three mature and one half-mature specimens from Norway. For information on specimen collection localities and GenBank accession numbers see Appendix 1.

Description.

Green worms (sometimes yellowish-green). Length (fixed worms) more than 7.9-10.6 mm (amputated specimens), first 15 segments 3.8-6.2 mm long, width at clitellum 0.74-1.05 mm. More than 23-41 segments. Chaetae straight or slightly sigmoid (Fig. 15A). Dorsal bundles with 3-6 chaetae anterior to clitellum, 3-5 chaetae in postclitellar segments. Ventral bundles with 3-6 chaetae anterior to clitellum, 3-5 chaetae posteriorly. Each worm’s longest measured chaetae 70-85 µm long, about 5 µm wide. Clitellum extending over XII–XIII. Head pore at 0/1. Epidermis with transverse rows of gland cells.

Coelomocytes numerous, 20-35 µm long, spindle-shaped, oval, round, granulated. Paired pharyngeal glands present in IV, V and VI; each pair converging dorsally (Fig. 15B). Dorsal vessel originating in XIII. Nephridia observed in VIII–X and XV–XIX, about 250 µm long, anteseptale funnel only, postseptale oval, tapering into posterior efferent duct. Brain with posterior incision.

Male genitalia paired (Fig. 15D). Testes originating in XI, extending forwards into X, with testis sacs forming regular club-shaped lobes. Sperm funnels in XI, 620-670 µm long, 320-350 µm wide, making them about twice as long as wide, funnels tapering towards vasa deferentia. Most of vasa irregularly coiled in XII, 25-30 µm wide. Penial bulbs round, 170-180 µm in diameter. Ovaries in XII. About five mature eggs present at a time.

Spermathecae (Fig. 15C) in V, club-shaped, with distinct ampulla. Ectal duct narrow, shorter than ampulla, abruptly widening into ampulla. Ampulla round. Sperm arranged in a compact central sphere in the ampulla as well as embedded in the wall of ampulla, creating a circle around the sphere. Spermathecae 265-320 µm long, 270-310 µm wide at widest part of ampulla. Gland cells surrounding ectal pore, forming compact mass, slightly lobed, whole glandular body 310-325 µm in diameter at its widest part. Gland cells also along the ectal duct. Up to four midventral subneural glands in XIV–XVII, 240-270 µm, 215-245 µm, 190-215 µm and 130 µm long, respectively; glands in XVII not observed in all specimens.

Geographical distribution including BOLD data.

Genetically identified from France and Norway. Previously described from Denmark, Norway ( Nurminen 1965b) the United Kingdom and Sweden ( Erséus 1977). BIN-number: BOLD:AAU1636.

Remarks.

Specimens in this study are smaller and possess somewhat fewer chaetae, than the ones from the original description by Stephenson and the later re-description by Nielsen and Christensen. Furthermore, the observed proportions of the sperm funnels (twice longer than wide) differ greatly from those (7-10:1, or 6-8:1) described by Stephenson and Nielsen and Christensen, respectively. However, folding of these organs may have caused us to underestimate their true length. Nevertheless, the distinct greenish colour of the sampled specimens and the resemblance between their spermathecae and particularly the one described by Nielsen and Christensen confirm these specimens as Lumbricillus viridis .

According to our knowledge, the presence of gland cells along the spermathecal ectal duct has not been reported for L. viridis before, possibly because of the difficulty of distinguishing these gland cells from the large ones surrounding the ectal pore. In this study, similar duct glands have only been observed in L. pagenstecheri sensu lato.

Lumbricillus viridis is genetically most closely related to the L. pagenstecheri species complex (Fig. 1: L. pagenstecheri A–D).