Lumbricillus knoellneri Nielsen & Christensen, 1959

Klinth, Marten J., Rota, Emilia & Erseus, Christer, 2017, Taxonomy of North European Lumbricillus (Clitellata, Enchytraeidae), ZooKeys 703, pp. 15-96 : 43-46

Lumbricillus knoellneri Nielsen & Christensen, 1959 Fig. 20

Lumbricillus knoellneri Nielsen & Christensen, 1959: pp. 106-107, figs 125-126, 130; Klinth et al. 2017.

Fridericia bulbosa ; sensu Knöllner 1935: p. 443; nec Rosa, 1887.

Type material.

Typus amissus (Nomenclatura Oligochaetologica). Type locality: Ebeltoft Vig, Denmark ( Nielsen and Christensen 1959). We did not designate a neotype as we do not have material from the type locality.

Material examined.

SMNH 152734 (CE980) & SMNH 152735 (CE982), two mature specimens from Sweden, and ZMBN 107859 (CE19369), ZMBN 107860 (CE20761), ZMBN 107861 (CE20762), ZMBN 107863 (CE22615), ZMBN 107865 (CE23252) & ZMBN 107866 (CE23253), four mature and two immature specimens from mainland Norway and Svalbard. For information on specimen collection localities and GenBank accession numbers see Appendix 1.

Description.

White to yellow worms. Length (fixed worms) more than 2.1-3.6 mm (amputated specimens), first 15 segments 1.6-1.9 mm long, width at clitellum 0.20-0.32 mm. More than 16-32 segments. Chaetae straight or slightly sig moid (Fig. 20A). Lateral bundles with 2 chaetae anterior to clitellum, 2 chaetae in postclitellar segments. Ventral bundles with 2-3 chaetae anterior to clitellum, 2 chaetae posteriorly. Each worm’s longest measured chaetae 25-50 µm long, about 3 µm wide. Clitellum extending over XII– 1/2XIII. Head pore at 0/1. Epidermis with transverse rows of gland cells.

Coelomocytes numerous, 10-25 µm long, spindle-shaped, oval, round, granulated with distinct nucleus. Paired pharyngeal glands present in IV, V and VI (Fig. 20B). Dorsal vessel originating in XIII–XV. Nephridia observed in VIII–X and XV–XXXII, about 70 µm long, anteseptale funnel only, postseptale oval, tapering into posterior efferent duct. Brain with posterior incision.

Male genitalia paired (Fig. 20D). Testes originating in XI, extending forwards into X, with testis sacs covering compact mass, slightly lobed but not regularly arranged. Sperm funnels in XI, 100-150 µm long, 70-155 µm wide, making them about as long as wide or 1.5 times longer than wide, funnels tapering towards vasa deferentia. Most of vasa irregularly coiled in XII, 5-10 µm wide. Penial bulbs round, 70-115 µm in diameter. Ovaries in XII. One to two mature eggs present at a time.

Spermathecae (Fig. 20C) in V, club-shaped, with distinct ampulla. Ectal duct more than twice the length of the ampulla, abruptly widening into ampulla. Ampulla round, entally connecting with oesophagus. Sperm in ampulla aggregated into central mass haloed by circle of spermatozoa. Spermathecae 145-270 µm long, 45-65 µm wide at widest part of ampulla. Gland cells surrounding ectal pore, divided in several small lobes, whole glandular body 75-100 µm in diameter at its widest part. Up to four midventral subneural glands in XIII– XVI, 50-65 µm, 35-65 µm, 35-65 µm and 35-60 µm long, respectively; glands in XVI not observed in all specimens.

Geographical distribution including BOLD data.

Genetically identified from Norway (mainland and Svalbard) and Sweden. Also known from Denmark and Germany. BIN-number: BOLD:ACM5261.

Remarks.

Lumbricillus knoellneri is described as having only 2 chaetae throughout the body but the newly studied material suggests that the preclitellar ventral bundles possess 2-3 chaetae. In fact, all of the eight studied specimens had 3 chaetae in at least 2 of the preclitellar ventral bundles, some in as many as 9. We found no pattern of this distribution and for each preclitellar ventral segment bearing chaetae ( II–XI), we found representatives with either 2 or 3 chaetae. This shows how variable this trait is and could explain the difference to the description by Nielsen and Christensen. However, it could also mean that our " L. knoellneri " is in fact another species. Many of the internal organs of L. knoellneri were as long as or even slightly longer than the ones in L. buelowi . This in combination with a generally smaller size caused the segments of L. knoellneri to appear more contracted. For a further discussion see the Remarks for L. buelowi above.

In 1985, Kossmagk-Stephan synonymized L. cervisiae (which he himself had described as a new species two years earlier) and L. christenseni Tynen, 1966 with L. knoellneri . All three species are small, have only two chaetae per bundle (at least according to the original descriptions) and similarly shaped spermathecae. However, L. christenseni has a sperm funnel that is 7-8 times longer than wide which is significantly longer than the 1.5 times measured in L. knoellneri . The sperm funnel of L. cervisiae is 3-4 times longer than wide which is also more than that of L. knoellneri . Furthermore, the testis sacs of L. cervisiae cover several small scattered lobes and the vasa deferentia extends backwards into XIII. Finally, L. cervisiae appears to be more slender than L. knoellneri and has significantly smaller internal organs, which we were able to discern by examining the mounted original material of Kossmagk-Stephan. Therefore, we reject the idea of L. cervisiae and L. christenseni being synonyms of L. knoellneri and treat them as separate species.