Paralumbricillus Klinth & Rota, 2024

Paralumbricillus Klinth & Rota View in CoL gen. nov.

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Lumbricillus Ørsted, 1844 View in CoL partim

Pachydrilus Claparède, 1861 View in CoL partim

Type species. Enchytraeus arenarius Michaelsen, 1889: pp. 12–14 View in CoL , figs 5a–d.

Included species:

Paralumbricillus arenarius ( Michaelsen, 1889) View in CoL comb. nov. Paralumbricillus bicornis View in CoL sp. nov.

Paralumbricillus bilobatus View in CoL sp. nov.

Paralumbricillus cervisiae ( Kossmagk-Stephan, 1983) comb. nov. Paralumbricillus christenseni ( Tynen, 1966) View in CoL comb. nov. Paralumbricillus crymodes ( Stephenson, 1922) View in CoL comb. nov. Paralumbricillus dubius ( Stephenson, 1911) View in CoL comb. nov. Paralumbricillus eltoni ( Stephenson, 1924) View in CoL comb. nov. Paralumbricillus eudioptus ( von Bülow, 1955) View in CoL comb. nov. Paralumbricillus lofotensis View in CoL sp. nov.

Paralumbricillus muscicolus ( Stephenson, 1924) View in CoL comb. nov. Paralumbricillus nielseni ( Nurminen, 1965) View in CoL comb. nov. Paralumbricillus sanguineus View in CoL sp. nov.

Paralumbricillus westheidei ( Kossmagk-Stephan, 1983) View in CoL comb. nov.

Etymology. The prefix para, Greek for “next to”, refers to the close phylogenetic relationship to Lumbricillus , in which most species have at some point been placed historically.

Genus description/diagnosis. White to yellow worms, about 5 to 20 mm in length. Prostomium hemispherical. Head pore at 0/1. Epidermis with transverse rows of gland cells. Chaetae straight or slightly sigmoid, without nodulus, usually 2 or 3 per bundle, rarely 4, upper bundles dorsolateral. Oesophageal appendages absent. Pharyngeal glands in three pairs, located in IV–VI, usually converging dorsally, sometimes connected dorsally, usually with ventral lobes, but secondary glands absent. Only nucleated coelomocytes present.

Dorsal vessel originating in XII–XIV. Nephridia with anteseptale made up of funnel only. Clitellum covering XII-XIII. Testis sacs, forming irregular lobes, sometimes budding off into free floating cysts. Penial bulbs compact or lobed. Midventral subneural glands usually present in XIII–XV, sometimes further back. Spermathecae in V, club- or pear-shaped, attached to and usually communicating with lumen of oesophagus; glands surrounding ectal pore. Mainly marine littoral but some species also found in limnic habitats.

Paralumbricillus bilobatus Klinth & Rota sp. nov. Figure 9 View Figure 9

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Holotype. NTNU-VM 74104 View Materials ( CE29420 ), Figs 9D–E View Figure 9 , an amputated mature specimen stained in paracarmine and mounted on a slide. COI barcode: BOLD NOENC414-18 .

Type locality. Beach west of road to Stavøya Island, Slettvik, Orkland, Trøndelag, Norway. Upper intertidal, sand and gravel near freshwater stream on beach. Coll. C. Erséus, 9 September 2016.

Other material examined. ZMBN 111482 View Materials ( CE26820 ) , ZMBN 153276 View Materials ( CE28319 ) , ZMBN 129228 View Materials ( CE32463 ) , ZMBN 153282 View Materials ( CE32464 ) and ZMBN 129338 View Materials ( CE33480 ) two mature, two partially mature and one immature specimen from Norway. For details on collection site and GenBank accession numbers see Table S1 .

Etymology. Referring to the bilobed structure of the penial bulbs.

Diagnosis. This species has a bilobed penial bulb, but unlike other Paralumbricillus species with bilobed bulbs, where one lobe is anterior and the other posterior, P. bilobatus sp.nov. has a dorsolateral and a ventromedial lobe. It is also one of the few Paralumbricillus species that regularly have ventral preclitellar bundles with up to 4 chaetae.

Description. Length of first 19–37 segments 2.9–5.9 mm (fixed, amputated specimens); first 15 segments (2.2) 2.4–3.5 mm long; width at clitellum (0.24) 0.39–0.46 mm. Chaetae straight or slightly sigmoid. Dorsolateral bundles with (1)2–3 chaetae anterior to clitellum, and 2 chaetae in postclitellar segments. Ventral bundles with 2–4 chaetae anterior to clitellum, and 2 chaetae in postclitellar segments. Each worm’s longest measured chaetae 55–95 µm long, about 5–10 µm wide. Clitellum extending over XII–XIII. Head pore not observed.

Coelomocytes, about 20–40 µm long, oval or spindle-shaped, granulated with distinct nucleus. Paired pharyngeal glands present in IV, V and VI, third pair sometimes extending into VII; each pair converging dorsally ( Figure 9A View Figure 9 ). Dorsal vessel originating in XIII. Nephridia observed in 7/8–9/10 and from 13/14 rearwards, about 90–165 µm long. Anteseptale small, consisting of funnel only. Postseptale oval, tapering into thin posteroventral efferent duct ( Figure 9B View Figure 9 ). Brain with posterior incision.

Male genitalia paired ( Figure 9C View Figure 9 ). Testes originating in XI, with developing sperm seemingly held together by testis sacs, forming irregular lobes. Sperm funnels in XI, sometimes extending back into XII, at least 540–990 µm long, 65–120 µm wide, making them about (5)9–15 times longer than wide (leaning towards the higher ratio due to the difficulties in measuring the total length in the mounted material), funnels tapering towards vasa deferentia. Large parts of vasa irregularly coiled around ovaries in XII, sometimes also extending backwards into XIII–XIV, vasa 10–15 µm wide. Penial bulbs bilobed with dorsolateral lobe 100–105 µm in diameter, and ventromedial lobe about 110 µm in diameter ( Figure 9D View Figure 9 ), vas entering dorsolateral lobe. One to two mature eggs observed.

Spermathecae ( Figure 9E View Figure 9 ; Table 2) in V, club-shaped, with a long ectal duct suddenly widening into ampulla. Ampulla oval, with sperm arranged in a tight ball. Ampulla entally connected to oesophagus. Spermathecae more than 195–210 µm long, 30–50 µm wide at the ectal duct, 105 µm wide at widest part of ampulla. Ectal pore at lateral line, surrounded by gland cells forming a somewhat lobed compact mass, glandular body up to 105 µm wide. One specimen with midventral subneural glands in XIII–XVIII, 50 µm, 50 µm, 55 µm, 55 µm, 65 µm and 55 µm long respectively.

Geographical distribution including BOLD data. Only known from the middle of Norway (Hordaland, Møre og Romsdal, Trøndelag and Nordland) .

Remarks. According to the species tree ( Figure 2 View Figure 2 ), this species is genetically close to P. arenarius and P. crymodes with which it shares the particularly long sperm funnels. However, the spermathecae of P. bilobatus sp. nov. have a long ectal duct, abruptly widening into the ampulla, whereas P. arenarius and P. crymodes have pear-shaped spermathecae with ducts gradually widening into the ampulla. Furthermore, the bilobed penial bulbs of P. bilobatus sp. nov. with dorsolateral and ventromedial lobes distinguish it from all other Paralumbricillus species.