Lumbricillus Ørsted, 1844

Lumbricillus Ørsted, 1844 View in CoL

Type species. Lumbricus lineatus Müller, 1774 .

Included species. See Table 1.

Lumbricillus elisae Klinth & Rota View in CoL sp. nov. Figure 4 View Figure 4

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Holotype. SMNH Type Coll. 9896 ( CE34782 ), Figures 4B, C, E View Figure 4 , an amputated mature specimen stained in paracarmine and mounted on a slide. COI barcode: BOLD NVENC1608-22 .

Type locality. Vilsund, Erslev, Nordjylland, Denmark. Upperintertidal, in shelly sand and decaying algae. Coll. M. Klinth & Elise Eriksson, 16 May 2018 .

Paratypes. SMNH Type Coll. 9897 ( CE1695 ) & SMNH Type Coll. 9898 ( CE1697 ) two mature specimens from Spain. For details on collection site and GenBank accession numbers see Table S1 .

Other material examined. SMNH 212150 ( CE 1876) an immature specimen from Sweden, and ZMBN 128876 ( CE 28299) an immature specimen from Norway. For details on collection site and GenBank accession numbers see Table S1.

Etymology. Named after the first author’s sister who collected the specimen we designate as the holotype.

Diagnosis. This species is distinguished from most other Lumbricillus species by a distinctly bilobed penial bulb. Lumbricillus sadovskyi Marcus, 1965 , and L. finisafricae Klinth, Rota & Erséus, 2022 have bilobed penial bulbs but with anterior and posterior lobes as opposed to the lateral and ventral lobes in L. elisae sp. nov. Lumbricillus bibulbus sp. nov. (see below) has similarly lobed penial bulbs but has spermathecae with glands along the ectal duct which L. elisae sp. nov. is lacking.

Description. Pinkish-orange worms. Length of first 11–36 segments 1.3–4.9 mm (fixed, amputated specimens); first 15 segments 2.1–3.1 mm long; width at clitellum 0.49–0.68 mm. Chaetae sigmoid. Dorsolateral bundles with 3–6 chaetae anterior to clitellum, 3–5 chaetae in postclitellar segments. Ventral bundles with 4–7 chaetae anterior to clitellum, 4–6 chaetae posteriorly. Each worm’s longest measured chaetae 55–90 µm long, about 5 µm wide. Clitellum extending over XII–XIII, difficult to discern proportion of coverage of XIII. Head pore at 0/1.

Coelomocytes numerous, 15–20 µm long, round or oval, granulated with distinct nucleus. Paired pharyngeal glands present in IV, V and VI; all pairs converging dorsally ( Figure 4A View Figure 4 ). Dorsal vessel originating in XIII or XIV. Nephridia observed in 7/8–8/9, about 95–110 µm long. Anteseptale small, consisting of funnel only. Postseptale oval, tapering into posteroventral efferent duct ( Figure 4B View Figure 4 ). Brain with posterior incision.

Male genitalia paired ( Figure 4C View Figure 4 ). Testes originating in XI, with testis sacs forming regular club-shaped lobes extending forwards into X or IX. Sperm funnels in XI, more than 285–420 µm long, 150–180 µm wide, making them at least 2–3 times longer than wide, funnels tapering towards vasa deferentia. Large parts of vasa irregularly coiled around ovaries in XII, vasa 15–20 µm wide. Penial bulbs bilobed with larger dorsolateral lobe 110–125 µm in diameter and smaller ventromedial lobe 90–100 µm in diameter ( Figures 4C–D View Figure 4 ), vas entering dorsolateral lobe. No mature eggs observed.

Spermathecae ( Figures 4E–F View Figure 4 ) in V, spindle-shaped, with short ectal duct rapidly widening into ampulla, the latter tapering into ental duct connected to oesophagus. Sperm filling lumen of ampulla. Spermathecae 190–265 µm long, 40–50 µm wide at the ectal duct, 80–95 µm wide at widest part of ampulla. Ectal pore at lateral line surrounded by gland cells forming compact, somewhat lobed mass, glandular body up to 135–180 µm wide. Three midventral subneural glands in XIII–XV, 65–100 µm, 80–100 µm and 45 µm long, respectively; gland in XV not observed in all specimens.

Geographical distribution including BOLD data. We find it quite remarkable that our five specimens of this seemingly rare species were found in four different countries, even though three are Scandinavian. Furthermore, there is a 99 % match on BOLD with a specimen collected in Shandong, China (private sequence, not yet published), where it has probably been introduced through shipping. This suggests that this species has a great capability for dispersal .

Remarks. In the phylogeny, this species is firmly nested within the lineatus group, closest to L. rutilus Welch, 1914 and L. lineatus . The spermathecae are reminiscent of many species within the lineatus group, but the distinctly bilobed penial bulbs distinguish this species from most others. As mentioned as an introductory remark under Taxonomy above, closer studies have shown that the penial bulbs of Lumbricillus are not perfectly round and that many species have a tendency for a larger dorsal and a smaller median lobe. However, in most cases said “lobes” are mere protrusions from a single compact bulb, whereas in this species they are clearly divided and only connected at the base, close to the male pore. The known species of Lumbricillus with clearly bilobed penial bulbs are Lumbricillus sadovskyi , L. finisafricae , L. bibulbus sp. nov. and possibly L. scoticus (see below). The two former species have anterior and posterior lobes, and the rest, including L. elisae sp. nov., have dorsolateral and ventromedial lobes. The male apparatus of L. scoticus is further complicated with an additional lobe/prostate gland and is discussed in more detail below. The penial bulbs of L. elisae sp. nov. are most similar to those of L. bibulbus sp. nov., but these two species can easily be differentiated by the morphology of their spermathecae, where L. bibulbus sp. nov. has glands along the ectal duct.

Lumbricillus boreas Klinth & Rota sp. nov. Figure 5 View Figure 5

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Holotype. ZMBN 129201 View Materials ( CE32320 ), Figure 5 View Figure 5 , an amputated mature specimen stained in paracarmine and mounted on a slide. COI barcode: BOLD NOENC415-18 .

Type locality. Atlanterhavsveien Road, W side of Geitøya Island , Averøy, Møre og Romsdal, Norway. Mid-intertidal, in coarse sand. Coll. C. Erséus & M. Klinth, 31 May 2017 .

Other material examined. ZMBN 128903 ( CE 28498) an immature specimen from Norway. For details on collection site and GenBank accession numbers see Table S1.

Etymology. Noun in apposition, from the Greek god of the North Wind.

Diagnosis. This species is a member of the lineatus group (see Table 1). In the spermathecae it resembles above all L. rivalis Levinsen, 1884 and L. rutilus , but can be separated from both by having shorter sperm funnels, i.e. about as long as wide as opposed to at least twice as long as wide.

Description. Length of first 19–20 segments 2.5 and 3.4 mm (two fixed, amputated specimens, respectively); first 15 segments 1.8 and 2.4 mm long; width at clitellum 0.35 mm. Chaetae sigmoid. Dorsolateral bundles with 3–7 chaetae anterior to clitellum, 4–7 chaetae in postclitellar segments. Ventral bundles with 3–7 chaetae anterior to clitellum, 4–7 chaetae posteriorly. Each worm’s longest measured chaetae 35–55 µm long, about 3 µm wide. Clitellum extending over 1/2XI–1/2XIII. Head pore not observed.

Coelomocytes numerous, 10–15 µm long, round or oval in shape, granulated with distinct nucleus. Paired pharyngeal glands present in IV, V and VI; all pairs converging dorsally ( Figure 5A View Figure 5 ). Dorsal vessel originating in XI–XIII. Nephridia observed in 7/8–8/9 and from 14/15 rearwards, about 55–70 µm long. Anteseptale small, consisting of funnel only. Postseptale oval, tapering into posteroventral efferent duct ( Figure 5B View Figure 5 ). Brain with posterior incision.

Male genitalia paired ( Figure 5C View Figure 5 ). Testes originating in XI, with testis sacs forming regular club-shaped lobes extending forwards into IX. Sperm funnels in XI, 125 µm long, 115 µm wide, making them about as long as wide, funnels tapering towards vasa deferentia. Large parts of vasa irregularly coiled around ovaries in XII, vasa 15 µm wide. Penial bulbs compact and round, 75 µm in diameter. One mature egg observed.

Spermathecae ( Figure 5D View Figure 5 ) in V, spindle-shaped, with short ectal duct clad in musculature and rapidly widening into ampulla. Ampulla with midway bend, dividing it into two parts, entally connected to oesophagus via tapering ental duct. Sperm in lumen of ampulla and more aggregated in ental part than in ectal part. Spermathecae 185–210 µm long, 20 µm wide at the ectal duct, 50–55 µm wide at widest part of ampulla. Ectal pore at lateral line surrounded by gland cells forming compact mass, glandular body up to 90–95 µm wide. One midventral subneural gland in XIV, 100 µm long.

Geographical distribution including BOLD data. Only known from Møre og Romsdal and Sogn og Fjordane in Norway .

Remarks. Despite only having one mature specimen we have decided to describe this new species based on its clear genetic delimitation and the good quality of the holotype slide. Lumbricillus boreas sp. nov. is clearly a member of the lineatus group and has a compact penial bulb, as do most other species in this assemblage. Its spermathecae are spindle-shaped and thus at least superficially similar to those of the other members of the group. Most similar are L. rivalis and L. rutilus and perhaps also the yet unidentified species F and G ( Klinth et al. 2017b), although the spermathecae of the two latter are only vaguely described due to poor slide mounts. All these four mentioned species do however have sperm funnels that are longer in relation to their width, at least 2 times longer than wide, whereas L. boreas sp. nov. has sperm funnels only about as long as wide. This character is known to vary with the contractions of the musculature and organs, when the worms are put in ethanol, and therefore, additional fully mature specimens of this species are required to determine how well this character distinguishes it from its close relatives.

Lumbricillus scoticus Elmhirst & Stephenson, 1926 Figure 6 View Figure 6

Lumbricillus scoticus Elmhirst & Stephenson, 1926: 469-473 View in CoL , figs.

1-3.

Lumbricillus scoticus View in CoL ; Christensen 1962: 8; Nurminen 1970: 206;

Tynen 1972: 28.

Non Lumbricillus scoticus View in CoL ; Erséus 1976: 9.

Material examined. SMNH 212160 ( SM 192) & SMNH 212161 ( SM 193) two mature specimens from Greenland. For information on collection localities and GenBank accession numbers for COI barcodes see Table S1.

Description. Length of first 23–25 segments 4.5 and 5.1 mm (two fixed, amputated specimens, respectively); first 15 segments 3.2 and 3.3 mm long; width at clitellum 0.68 and 0.82 mm. Chaetae sigmoid. Dorsolateral bundles with 6–10 chaetae anterior to clitellum, 8–10 chaetae in postclitellar segments. Ventral bundles with 10–14 chaetae anterior to clitellum, 9–13 chaetae posteriorly. Each worm’s longest measured chaetae 135–140 µm long, about 8–10 µm wide. Clitellum extending over XII–3/4XIII. Head pore at 0/1.

Coelomocytes numerous, 20–25 µm long, round, oval or spindle-shaped, granulated with distinct nucleus, in one specimen deeply stained. Paired pharyngeal glands present in IV, V and VI; first two pairs converging dorsally ( Figure 6A View Figure 6 ). Dorsal vessel originating in XI. Nephridia observed in 7/8 and from 14/15 rearwards, about 115–170 µm long. Anteseptale small, consisting of funnel only. Postseptale oval, tapering into posteroventral efferent duct ( Figure 6B View Figure 6 ). Brain with posterior incision.

Male genitalia paired ( Figure 6C View Figure 6 ). Testes originating in XI, with testis sacs forming club-shaped lobes extending forwards into X, lobes not arranged in a typical fan shape. Sperm funnels in XI, slightly lobed and not entirely cylindrical, at least 500–525 µm long, 240–260 µm wide, making them at least twice as long as wide, but probably closer to 3 or 4 times longer than wide in living specimens, funnels tapering towards vasa deferentia. Large parts of vasa irregularly coiled around ovaries in XII, vasa 25–30 µm wide. Male apparatus divided into distinct parts, from male pore a round muscular structure extends dorsolaterally through which the vas deferens connects with the pore. Into the muscular structure two glandular organs connect, one large round bulb positioned dorsomedially, and one smaller pear-shaped bulb anterior to the muscular structure. The diameter of the muscular structure 205–230 µm; large bulb 180–260 µm, and small bulb 85–120 µm. Five to six maturing eggs observed.

Spermathecae ( Figure 6D View Figure 6 ) in V, spindle-shaped, with ectal duct gradually widening into ampulla. Ampulla bent, entally sac-like, connection to oesophagus not distinguishable. Sperm in lumen of duct and ampulla, with heads aggregated in wall of ental part of ampulla. Spermathecae 340–400 µm long, 60–105 µm wide at the ectal duct, 135–150 µm wide at widest part of ampulla. Ectal pore at lateral line surrounded by gland cells forming deeply lobed mass, glandular body up to 265–285 µm wide. No midventral subneural glands observed.

Geographical distribution including BOLD data. Reported from Great Britain ( Scotland and Wales), Iceland and Greenland.

Remarks. Our two specimens from Greenland greatly resemble the original description of L. scoticus from Scotland. The size, high number of chaetae and most notably the shape of the penial bulbs suggest that our specimens belong to the same species. The penial bulbs have a unique morphology, not known from any other Lumbricillus species, and are described in great detail, although not depicted, in the original description. Elmhirst & Stephenson distinguish in the bulbs six rough parts (a-f), where we could clearly make out (a) where the vas deferens passes through the penial body, (c) the mass of cells that we call the dorsomedial bulb, (d) a pear-shaped gland on the anterior of the penial body, (e) the muscular capsule, and (f) the scattered cells and musculature in between the other parts. Elmhirst & Stephenson also describe (b) a tubular cavity from which (c), the main glandular mass, expands. We could not clearly make this out in our whole mounts but we can assume that the secretions produced in this main bulb are transported through an internal cavity towards the vas deferens and the pore, and that this structure only becomes apparent in sectioned material. Furthermore, the muscular capsule (e) is said to surround “the greater part of the mass” but not the pear-shaped gland (d), whereas we interpret it as being separate from not only the pear-shaped gland but also the larger dorsomedial bulb and mainly surrounding the vas deferens. That said, we did observe other musculature connecting all the different parts of the penial apparatus and still consider our specimens as belonging to L. scoticus .

Lumbricillus scoticus was originally described from the shores of Great Cumbrae Island in Scotland, and later from other parts of Great Britain ( Tynen 1972). Christensen (1962) and Erséus (1976) reported it from Iceland, but subsequently, having studied type material, Erséus concluded his findings to belong to another species ( Erséus 1977). Nurminen (1970) reported it from the west coast of Greenland close to where we got our samples.

Lumbricillus bibulbus Klinth & Rota sp. nov. Figure 7 View Figure 7

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Holotype. ZMBN 153439 View Materials ( CE28409 ), Figures 7A & E View Figure 7 , an amputated mature specimen stained in paracarmine and mounted on a slide. COI barcode: BOLD NOENC411-18 .

Type locality. Sulesund, Sula, Møre og Romsdal, Norway. Mid-intertidal, in sand and gravel under stones on boulder beach. Coll. C. Erséus, 29 July 2016 .

Paratypes. ZMBN 128888 View Materials ( CE28408 ) , ZMBN 153277 View Materials ( CE28410 ) & ZMBN 153278 View Materials ( CE28411 ) three mature specimens from the type locality. For details on collection site and GenBank accession numbers see Table S1.

Etymology. The name is Latin for two bulbs, referring to the bilobed penial bulbs of this species.

Diagnosis. This species can be distinguished from other Lumbricillus species by a combination of bilobed penial bulbs and spermathecae with both an ectal gland and glands along the ectal duct.

Description. Yellowish worms. Length of first 17–30 segments 2.5–4.3 mm (fixed, amputated specimens); first 15 segments 1.7–2.2 mm long; width at clitellum 0.33–0.39 mm. Chaetae sigmoid. Dorsolateral bundles with (2)3–4 chaetae anterior to clitellum, 2–5 chaetae in postclitellar segments. Ventral bundles with 3–6 chaetae anterior to clitellum, 3–5 chaetae posteriorly. Each worm’s longest measured chaetae 55–60 µm long, about 5 µm wide. Clitellum extending over XII–1/2XIII. Head pore at 0/1.

Coelomocytes numerous, 15–20 µm long, round or oval, granulated with distinct nucleus. Paired pharyngeal glands present in IV, V and VI; first and second pairs converging dorsally ( Figure 7A View Figure 7 ). Dorsal vessel originating in XVII. Nephridia observed in 7/8–9/10 and from 13/14 rearwards, about 75–130 µm long. Anteseptale small, consisting of funnel only. Postseptale oval, tapering into posteroventral efferent duct ( Figure 7B View Figure 7 ). Brain with posterior incision.

Male genitalia paired ( Figure 7C View Figure 7 ). Testes originating in XI, with testis sacs forming regular club-shaped lobes extending forwards into IX. Sperm funnels in XI, 135–180 µm long, 65–90 µm wide, making them about 1.5 or 3 times longer than wide, funnels tapering towards vasa deferentia. Large parts of vasa irregularly coiled around ovaries in XII, vasa 10 µm wide. Penial bulbs bilobed with dorsolateral lobe and ventromedial lobe ( Figure 7C View Figure 7 ), both lobes 75–130 µm in diameter, vas entering dorsolateral lobe. One to two mature eggs present at a time.

Spermathecae ( Figure 7D View Figure 7 ) in V, spindle-shaped, with short ectal duct rapidly widening into round ampulla, followed by tapering ental duct connected to oesophagus. Ball of sperm in lumen of ampulla. Spermathecae 80–120 µm long, 20–35 µm wide at the ectal duct, 50–85 µm wide at widest part of ampulla. Ectal pore at lateral line surrounded by gland cells forming compact mass, glandular body up to 80–95 µm wide; glands also along the ectal duct. Two midventral subneural glands in XIV–XV, 55–65 µm and 65 µm long, respectively; not observed in all specimens.

Geographical distribution including BOLD data. Only known from the type locality in Møre og Romsdal, Norway .

Remarks. At a first glance this new species of Lumbricillus is reminiscent of L. pagenstecheri ( Ratzel, 1868) and the many species that resemble it morphologically. This similarity comes mainly from the spermatheca, which not only has an ectal gland but also glands along the ectal duct, a character shared by the more than 20 species that make up the pagenstecheri group. However, unlike L. pagenstecheri s. lat., the spermatheca of L. bibulbus sp. nov. has a distinct ectal duct and quite large ental duct. The caliber and length of the ectal duct of L. pagenstecheri s. lat. can hardly be made out, usually only the thin lumen of the duct is visible among the dense glands along the duct. More importantly, L. bibulbus sp. nov. has a bilobed penial bulb, neither seen in the pagenstecheri group nor in most Lumbricillus species. Backlund (1947) did describe a Pachydrilus lineatus with a bilobed penial bulb, but its spermathecae seem more reminiscent of L. latithecatus Klinth, Rota & Erséus, 2017b and completely different from those of L. bibulbus sp. nov. Also, Lumbricillus sadovskyi from South America, and L. finisafricae from South Africa have bilobed penial bulbs, but similarly to L. latithecatus they have spermathecae that lack glands along the ectal duct and do not have an ampulla as clearly set off from the duct as in L. bibulbus sp. nov. Genetically, this new species is not found as sister to the other species in the pagenstecheri group but rather as sister to the lineatus group ( Figure 2 View Figure 2 ).