Lumbricillus buelowi Nielsen & Christensen, 1959

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

Lumbricillus buelowi Nielsen & Christensen, 1959 Fig. 19

Lumbricillus buelowi Nielsen & Christensen, 1959: pp. 106, figs 121-124 & 129; Erséus et al. 2010; Klinth et al. 2017.

Fridericia bulbosa ; sensu von Bülow 1957: pp. 87-88, pl. XXVII, figs 5-11; nec Rosa, 1887.

Type material.

Typus amissus (Nomenclatura Oligochaetologica). Type locality not precisely defined; the species was originally described from four different sites ( Kalø, Femmøller, Ebeltoft and Avedøre) in Denmark ( Nielsen and Christensen 1959). We did not designate a neotype as we do not have material from any of the type localities.

Material examined.

SMNH 152719 (CE5224), one mature specimen from Sweden, and ZMBN 107802 (CE22293), ZMBN 107804 (CE23273), ZMBN 107805 (CE23375), ZMBN 107806 (CE23376), ZMBN 107811 (CE24678), ZMBN 107814 (CE24688) & ZMBN 107816 (CE24690), seven mature specimens from Norway. For information on specimen collection localities and GenBank accession numbers see Appendix 1.

Geographical distribution including BOLD data.

Genetically identified from Norway and Sweden. Also known from Denmark and Germany. BIN-number: BOLD:ACQ3084.

Description.

White to slightly pink or yellow worms. Length (fixed worms) more than 2.4-5.2 mm (amputated specimens), first 15 segments 1.7-2.4 mm long, width at clitellum 0.28-0.49 mm. More than 21-32 segments. Chaetae straight or slightly sigmoid (Fig. 19A). Lateral bundles with 2-3 chaetae anterior to clitellum, 2(3) chaetae in postclitellar segments. Ventral bundles with 2-3(4) chaetae anterior to clitellum, 2(3-4) chaetae posteriorly. Each worm’s longest measured chaetae 30-55 µm long, about 5 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; each pair converging dorsally (Fig. 19B). Dorsal vessel originating in XIV. Nephridia observed in VIII–X and XV–XXVIII, about 95 µm long, anteseptale funnel only, postseptale oval, tapering into posterior efferent duct. Brain slightly longer than wide, with posterior incision.

Male genitalia paired (Fig. 19D). Testes originating in XI, extending forwards into X, with testis sacs covering compact mass, slightly but not regularly lobed. Sperm funnels in XI, 85-140 µm long, 100-145 µm wide, making them about as long as wide, funnels tapering towards vasa deferentia. Most of vasa irregularly coiled in XII, 5-10 µm wide. Penial bulbs round, 75-110 µm in diameter, everted in one specimen. Ovaries in XII. One to three mature eggs present at a time.

Spermathecae (Fig. 19C) in V, club-shaped, with distinct ampulla. Ectal duct narrow, 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 130-160 µm long, 45-65 µm wide at widest part of ampulla. Gland cells surrounding ectal pore, folded, glandular body 40-90 µm in diameter at its widest part. Up to five midventral subneural glands in XIII– XVII, 50-95 µm, 60-120 µm, 60-95 µm, 50-65 µm and 45 µm long, respectively; glands in XVI–XVII not observed in all specimens.

Geographical distribution including BOLD data.

Genetically identified from Norway and Sweden. Also known from Denmark and Germany. BIN-number: BOLD:ACQ3084.

Remarks.

It is clear that the two species here identified as L. buelowi and L. knoellneri Nielsen & Christensen, 1959 are closely related ( Klinth et al. 2017) (see also Fig. 1), and most morphological characters such as the spermathecae, sperm funnels and penial bulbs are virtually identical between them. However, there are some general differences in our studied material: L. buelowi is on average larger than L. knoellneri , as originally noted by Nielsen and Christensen, although there is overlap between the two. Lumbricillus buelowi possesses 2-3 chaetae in the lateral bundles anterior of the clitellum while L. knoellneri possesses only 2. In their original description, Nielsen and Christensen also differentiate the two species by colour and size of coelomocytes where L. buelowi is red with two types of coelomocytes, one being larger than the chaetae, compared with L. knoellneri which is white and have only one type of coelomocytes, shorter than the chaetae. We observed only the smaller coelomocytes in both species, and as we stained the material we only have observations of the live animals; some specimens of L. buelowi were noted as being pinkish.

There are a number of species with descriptions similar to the ones of L. buelowi , and therefore also of L. knoellneri , such as L. eltoni (Stephenson, 1924), L. muscicolus (Stephenson, 1924) and L. nielseni Nurminen, 1965. All these latter three were described from Svalbard where we found specimens of L. knoellneri but not L. buelowi . Unfortunately, the two species described by Stephenson (1924) were not illustrated and the descriptions are not extensive enough for us to synonymize either of them with L. knoellneri ( Stephenson’s species would in that case hold seniority in name). Also L. nielseni was described too briefly ( Nurminen 1965a) and the illustrated spermathecae seems slightly different from those of L. buelowi and L. knoellneri , causing us once again to avoid synonymization.