Lumbricillus latithecatus, Klinth, Marten J., Rota, Emilia & Erseus, Christer, 2017

Klinth, Marten J., Rota, Emilia & Erseus, Christer, 2017, Taxonomy of North European Lumbricillus (Clitellata, Enchytraeidae), ZooKeys 703, pp. 15-96 : 23-24

Lumbricillus latithecatus sp. n. Figs 3B, 5

" Lumbricillus lineatus L1"; BOLD (unpublished records)

Lumbricillus sp. E; Klinth et al. 2017.

? Pachydrilus lineatus ; sensu Backlund 1947: pp. 3-5, figs 1-2.

Holotype.

ZMBN 107940 (CE12041), a whole-mounted voucher of a sexually mature and DNA-barcoded worm (COI barcode is KU894054 in NCBI/GenBank; Klinth et al. 2017).

Type locality.

Norway, Rogaland, Sola, Ölbörhamna, intertidal in decomposing algae, 58.8697N, 5.5654E, collected 15 June 2012 by C. Erséus. Norway.

Paratype.

ZMBN 107941 (CE12042), one whole-mounted sexually mature specimen from the type locality.

Other material examined.

SMNH 152830 (CE1976) & SMNH 152831 (CE1979), two mature specimens from Sweden. For information on specimen collection localities and GenBank accession numbers see Appendix 1.

Etymology.

Named from the Latin latus meaning wide and theca for spermatheca.

Diagnosis.

This species can be distinguished from other Lumbricillus species by the shape of the spermathecae, which do not gradually widen from the ectal pore but instead originates from a very wide pore followed by an ectal duct and ampulla of even width throughout. This makes the duct and ampulla of the spermathecae virtually indistinguishable. There is at least a superficial similarity to the spermathecae of Lumbricillus lineatus and L. verrucosus with a midway constriction or bend and sperm aggregated in the ental part of the ampulla (Fig. 3). However, the spermathecae of L. lineatus and L. verrucosus have ectal pores that are much smaller than the diameter of their ampullae, giving the impression of a rapid widening of the spermathecae after the ectal pore, even though the duct and ampulla are difficult to distinguish also in these species.

Description of all material.

Length (fixed worms) more than 2.5-7.8 mm (amputated specimens), first 15 segments 2.5-4.7 mm long, width at clitellum 0.42-0.85 mm. More than 15-27 segments. Chaetae slightly sigmoid (Fig. 5A). Dorsal bundles with (3)4-8(9) chaetae anterior to clitellum, 3-7 chaetae in postclitellar segments. Ventral bundles with 5-10 chaetae anterior to clitellum, 4-9 chaetae posteriorly. Each worm’s longest measured chaetae 60-75 µm long, about 4-5 µm wide. Clitellum extending over XII–XIII. Head pore not observed. Epidermis with transverse rows of gland cells.

Coelomocytes numerous, 10-25 µm long, round, oval or spindle-shaped, granulated. Paired pharyngeal glands present in IV, V and VI; each pair converging dorsally (Fig. 5B). Dorsal vessel originating in XIII. Nephridia examined in IX and XIV–XXV, about 75-155 µm long. Anteseptale small, consisting of funnel only. Postseptale oval, tapering posteriorly into efferent duct. Brain with posterior incision.

Male genitalia paired (Fig. 5D). Testes originating in XI, extending forwards into IX, with testis sacs forming regular club-shaped lobes. Sperm funnels in XI, sometimes extending into X or XII, 360-1300 µm long, 155-235 µm wide, making them about 2-6 times longer than wide, funnels tapering towards vasa deferentia. Most of vasa irregularly coiled in XII, 15-30 µm wide. Penial bulbs round, 155-285 µm in diameter, possibly with a small ventral lobe set off from the rest of the bulb. Ovaries in XII. One to four mature eggs present at a time.

Spermathecae (Figs 3B, 5C) in V, pouch-shaped, without distinct ampulla. Ectal duct seemingly indistinguishable from ampulla as the wide pore is followed by a lumen that remains about the same width or possibly widening slightly. Ectal pore surrounded by mass of gland cells forming compact body 140-325 µm in diameter at its widest part. Ampulla, with possible constriction midway dividing it into two sections; ental connection with oesophagus. Sperm filling middle of ectal duct, heads of spermatozoa embedded and forming aggregates mainly in ental part of ampulla. Each spermatheca altogether 220-410 µm long, 65-160 µm wide at widest part of ampulla. Up to three midventral subneural glands in XIII–XV, 80-200 µm, 100-250 µm and 115 µm long, respectively; glands in XIV and XV not observed in all specimens.

Details of holotype.

The largest specimen of the lot. Length 7.8 mm (amputated specimen), first 15 segments 4.7 mm long, width at clitellum 0.85 mm. 27 segments. Dorsal bundles with 5-8 chaetae anterior to clitellum, 4-7 chaetae in postclitellar segments. Ventral bundles with 5-10 chaetae anterior to clitellum, 5-9 chaetae posteriorly. Longest measured chaetae 75 µm long, about 5 µm wide. Clitellum extending over XII– 1/2XIII.

Coelomocytes 10-25 µm long. Dorsal vessel originating in XIII. Nephridia observed in IX and XXIII–XXV, about 125-135 µm long.

Testis sacs extending forwards into IX. Sperm funnels in XI, 1100 µm long, 210 µm wide, making them about 5 times longer than wide. Vasa deferentia 30 µm wide. Penial bulbs 285 µm in diameter. No mature eggs present.

Spermathecae (Fig. 3B) 335 µm long, 135 µm wide at widest part of ampulla. Glandular body at ectal pores 275 µm in diameter at its widest part. Midventral subneural glands in XIII and XIV, 200 µm and 150 µm long, respectively.

Geographical distribution including BOLD data.

Genetically identified from Norway and Sweden; also recognized from Denmark (BIN-number BOLD:AAU0294).

Remarks.

The measured lengths of the sperm funnels are probably underestimated due to the difficulty of tracing them through the worms and due to folding. The two Swedish specimens were somewhat smaller than the Norwegian ones, and their funnels folded and only measurable for about 360 µm, but the length:width ratio was close to 4-6:1, as noted for the Norwegian specimens.

The description of Pachydrilus lineatus by Backlund (1947), from a drainpipe in Southern Sweden, in some ways reminds of our new species. Backlund was uncertain if his species belonged to P. lineatus because of the very wide spermathecal duct (which seemed as wide at the pore as in its medial part), the lack of a distinct ampulla and the possession of a large gland around the ectal pore. Furthermore, he described the penial bulbs as bilobed with a larger dorsal and a smaller ventral lobe. The description of the spermathecae sounds like the one of those of L. latithecatus , and after having examined the penial bulbs in the whole-mounted specimens of the latter species, it seems as if there could be a small lobe hidden behind the large spherical lobe (when viewed laterally). However, we would need transverse sections to truly compare this character to that which Backlund described. Lastly, Backlund reported small pharyngeal glands without dorsal development, which does not match with what we have observed for our species. Therefore, we are not certain as to the identity of Backlund’s P. lineatus .

Lumbricillus latithecatus is genetically most closely related to L. lineatus and L. rutilus (Fig. 1).