Claparedrilus semifuscoides, 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 : 51-55

Claparedrilus semifuscoides sp. n. Fig. 24

Marionina semifusca ; sensu Stephenson 1911: pp. 35-39, figs 2-3, pl. I, fig. 2.

Lumbricillus semifuscus ; sensu Nielsen and Christensen 1959: p. 96; Erséus 1976: pp. 8-9, figs 5-6; Finogenova and Timm 1988: pp. 94-96, figs 2-4; Klinth et al. 2017; Martinsson et al. 2017.

? Marionina semifusca ; sensu Southern 1907: p. 71; Southern 1909: pp. 148-149, pl. X, figs 9 a–c.

? Lumbricillus semifuscus ; Nurminen 1965a: p. 6.

Non Pachydrilus semifuscus Claparède, 1861: pp. 76-79, pl. II, figs 1-5.

Non Marionia semifusca ; Michaelsen 1889: p. 29.

Non Marionina semifusca ; Michaelsen 1900: p. 76.

Non Enchytraeoides semifuscus ; Michaelsen 1927: p. 13, fig. 12; von Bülow 1957: p. 86.

Holotype.

SMNH Type-8932 [former SMNH 152823] (CE2249), a whole-mounted voucher of a sexually mature and DNA-barcoded worm (COI barcode is KU893995 in NCBI/GenBank; Klinth et al. 2017).

Type locality.

United Kingdom, Wales, Anglesey, Beaumaris, intertidal zone of beach with sand and algae, 53.2623 N, 4.0914 W, collected 15 Febuary 2007 by M. Strand and P. Sundberg.

Paratypes.

SMNH Type-8933 [former SMNH 152821] (CE2247), SMNH Type-8934 [former SMNH 152822] (CE2248), SMNH Type-8935 [former SMNH 152825] (CE2252), all whole-mounted sexually mature specimen from the type locality.

Other material examined.

ZMBN 107908 (CE23750) & ZMBN 107912 (CE24657), one mature and one half mature specimen from Norway. For information on specimen collection localities and GenBank accession numbers see Appendix 1.

Etymology.

Named after its similarity to Claparedrilus semifuscus , which it has previously been confused with and misidentified as.

Diagnosis.

This species can be distinguished from C. semifuscus by the size of the penial bulbs. In C. semifuscus , the bulbs are much larger than the sperm funnels, whereas in C. semifuscoides they are of about the same size as the funnels or smaller.

Description.

White, grey to pinkish worms. Length (fixed worms) more than 4.0-7.3 mm (amputated specimens), first 15 segments 2.1-3.4 mm long, width at clitellum 0.54-0.69 mm. More than 22-45 segments. Chaetae sigmoid or straight (Fig. 24A). Dorsal bundles with 2-5(6) chaetae anterior to clitellum, 2-5(6) chaetae in postclitellar segments. Ventral bundles with 3-6 chaetae anterior to clitellum, 2-5 chaetae posteriorly. Each worm’s longest measured chaetae 85-115 µm long, about 5-8 µm wide. Clitellum extending over XII– 1/2XIII, sometimes XIII. Head pore at 0/1. Epidermis with transverse rows of gland cells.

Coelomocytes numerous, 10-20 µm long, spindle-shaped, oval, round, granulated with distinct nucleus. Paired pharyngeal glands 4 pairs, in IV, V, VI and VII, respectively; each pair converging but not connected dorsally (Figs 24 B–C), pair in IV with dorsal lobes only, pair in V with both dorsal and ventral lobes, pairs in VI and VII large and compact, but dorsal lobes difficult to distinguish from potential ventral ones. Dorsal vessel originating in XIII. Nephridia (Figs 24 F–G) observed in VI–VIII and XIV and onwards, 65-130 µm long, with various shapes, anteseptale with funnel on a thin stalk, postseptale oval, tapering into efferent duct which seems to originate either terminally or from posterior of the midventral of the postseptale (compare Figs 24 F–G). Brain with posterior incision.

Male genitalia paired (Fig. 24E). Testes originating in XI, with testis sacs enclosing compact sperm mass with numerous inconspicuous, irregularly arranged lobes, extending forwards into X, in some specimens extending into IX and XII. Sperm funnels in XI, 125-160 µm long, 110-145 µm wide, making them 1-1.5 times longer than wide, funnels tapering towards vasa deferentia. Most of vasa irregularly coiled in XII, 10-15 µm wide. Penial bulbs round, 140-155 µm in diameter. Ovaries in XII. Two to five mature eggs present at a time.

Spermathecae (Fig. 24D) in V, club-shaped, with distinct ampulla. Ectal pore midlateral. Ectal duct seemingly divided into two zones by intermediary layer of musculature. The outer zone, or coelomic lining, covering muscular layer, containing large, clearly defined nuclei. The inner zone, which is the epithelium and cuticle, lining muscular layer, appearing to be made up by numerous fine lines (perpendicular to the duct axis); these lines possibly epithelial cells or their nuclei, or microvilli crossing the cuticle. Duct twice as long as ampulla, abruptly widening into ampulla. Ampulla round, entally connecting with oesophagus, and containing irregular mass of sperm in postcopulatory specimens. Spermathecae 240-270 µm long, 60-110 µm wide at widest part (the ampullae). Gland cells surrounding ectal duct near spermathecal pore, forming compact mass, 50-105 µm in diameter at its widest part. Two midventral subneural glands in XIV–XV, 40-100 µm, 70-85 µm long, respectively.

Geographical distribution.

Genetically identified from Norway and the United Kingdom. Also known (by morphology) from Iceland ( Erséus 1976) and Sweden ( Erséus 1977).

Remarks.

In 1861, Claparède described Pachydrilus semifuscus from the Hebrides in Scotland. Due to its unusual and confusing morphology, this species has been moved around among some enchytraeid genera. It was transferred to Marionina ( Michaelsen 1900), then to Enchytraeoides ( Michaelsen 1927), and finally to Lumbricillus ( Nielsen and Christensen 1959). The original description focused almost entirely on the reproductive organs and noted sperm funnels about 1.5 times longer than wide, spermathecae with a long thin duct and clearly separated ampulla, nephridia with anteseptales made up of funnels only, and large kidney-shaped penial bulbs. Southern (1909), studying material from Dublin Bay (Ireland) and Edinburgh (Scotland), added that his specimens had 4-5 chaetae per bundle, a concave posterior of the brain, five pairs of pharyngeal glands in IV–VII (two of them in V), but with cylindrical rather than kidney shaped penial bulbs. Stephenson (1911) also recorded this species from Scotland but then increased the number of chaetae to 4-8 per bundle. He agreed with Southern’s description of the pharyngeal glands but questioned the shape of the penial bulbs, which he found to be spherical and not unusually large, compared to the descriptions by Claparède and Southern. In 1976, Erséus described the species from Iceland, also with pharyngeal glands in IV–VII, but with fewer chaetae per bundle and with anteseptales of the nephridia made up of a few coils as well as the funnels. Having studied our material, which is partly from Wales, we are confident that we have the same species as the one studied by Stephenson, Erséus, and possibly Southern, but that this (new) species is different from the original Pachydrilus semifuscus . Considering the way that it has been misidentified throughout history, we have named it semifuscoides and, at the same time, established a new genus for it called Claparedrilus . However, based on the similarities in the spermathecae and nephridia, we have decided to also transfer L. semifuscus into this genus, making it C. semifuscus ( Claparède, 1861) comb. nov.

Claparedrilus semifuscoides can be separated from C. semifuscus by the size of the penial bulbs, where the former species have bulbs about the same size as the sperm funnels (about 150 µm in diameter) whereas the latter have bulbs larger than the funnels; they are 400-500 µm long. The nephridium illustrated by Claparède is reminiscent of what we observed (Fig. 24 F–G), although our specimens seem to have the septa further back in relation to the funnel, making the funnel appear with a thin stalk, and with the efferent duct originating much further back on the postseptale. Unfortunately, Claparède did not mention the number of chaetae, subneural glands, or pharyngeal glands for his species, which makes its placement into the new genus Claparedrilus a bit tentative. This, and the fact that we have no genetic information for C. semifuscus , are the reasons why we designated the new taxon, C. semifuscoides , as the type species of the new genus.

Our specimens of C. semifuscoides are smaller than the ones described by Stephenson as M. semifusca , and they possess fewer chaetae, but we still believe that they belong to the same species. Stephenson remarks that (1) the nephridia can be found from V, (2) the anteseptale is made up of funnel only, and (3) the efferent duct extends backwards towards the pore, not forwards as illustrated by Claparède for C. semifuscus . We found nephridia from VI (possibly not finding any in V because they were obscured by the pharyngeal glands) and observed that the anteseptale consists of a funnel on a thin stalk. As this character was difficult to see and because there is no true nephridial tissue anterior to the septa this could still have been interpreted by Stephenson as a funnel only. We found that the efferent duct extended forward towards the pore which is more in agreement with Claparède’s illustration of C. semifuscus than what Stephenson noted, but the interpretation of this character may differ as the animal extends or contracts. Finally, Stephenson stated that the efferent duct originates well in front of the middle of the postseptale, whereas we observed it originating behind the middle or even from the posterior end. However, Stephenson also noted that this was not apparent in living specimens and only became clear from sections, which we have not studied.

Our specimens of C. semifuscoides also largely agree with Southern’s account of M. semifusca except for his description of the cylindrical penial bulbs. It is possible that the bulbs he studied were everted (as illustrated for L. pagenstecheri A in the present study; Fig. 14), which may have given the impression of them being cylindrical rather than spherical. Unfortunately, Southern did not mention the exact size of the bulbs or their size in relation to that of the sperm funnels, which makes us unable to confidently conclude that his species is the same as ours.

The species reported as L. semifuscus from Iceland ( Erséus 1976) is probably the same as our C. semifuscoides , as Erséus noted the four pairs of pharyngeal glands and an anteseptale with more than just a funnel. From his sectioned material he stated that the anteseptal portion was made up of a few coils of the nephridial canal in addition to the funnel, something we could not make out in our whole-mounted material. Another illustrated nephridium that resembles the one in our species was provided by Finogenova and Timm (1988) who reported L. semifuscus from the White Sea (Russia). Their description only differs from that of C. semifuscoides in reporting three pairs of pharyngeal glands, with the third pair extending into VII, but this could be a misinterpretation of a fourth pair. As we have not examined their material, we cannot be certain that this is the case, but we find it highly probable that they actually were describing C. semifuscoides . Finally, we are not certain about the identity of the species " Lumbricillus semifuscus " that Nurminen (1965a) reported from Spitsbergen (Svalbard), as he mentions sperm funnels "considerably longer than 1.5 times the width".

Compared to the species of Lumbricillus , i.e., the genus in which we previously placed this species (and erroneously referred to it as L. semifuscus ), C. semifuscoides can be distinguished mainly by its four pairs of pharyngeal glands, the stalked nephridial funnel, and the irregularly lobed testes.