Lumbricillus sp. H

Klinth, Marten J., Rota, Emilia & Erseus, Christer, 2017, Taxonomy of North European Lumbricillus (Clitellata, Enchytraeidae), ZooKeys 703, pp. 15-96 : 47-50

Lumbricillus sp. H Fig. 22

Lumbricillus sp. H; Klinth et al. 2017.

Material examined.

ZMBN 107945 (CE23136), ZMBN 107947 (CE24967) & ZMBN 107948 (CE24968), three half mature specimens from Norway. For information on specimen collection localities and GenBank accession numbers see Appendix 1.

Description.

White to orange worms. Length (fixed worms) more than 3.8-5.4 mm (amputated specimens), first 15 segments 2.0-2.8 mm long, width at clitellum 0.40-0.42 mm. More than 31-33 segments. Chaetae straight or slightly sigmoid (Fig. 22A). Lateral bundles with 2-3 chaetae anterior to clitellum, 2 chaetae in postclitellar segments. Ventral bundles with 2-3 chaetae anterior to clitellum, 2 chaetae posteriorly. Each worm’s longest measured chaetae 70-75 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, 15-20 µm long, spindle-shaped, oval, round, granulated with distinct nucleus. Paired pharyngeal glands present in IV, V and VI, sometimes extending into VII; each pair converging dorsally (Fig. 22B). Dorsal vessel originating in XIII. Nephridia observed in XIII–XXVIII, 100-145 µm long, anteseptale funnel only, postseptale oval, tapering into efferent duct. Brain with posterior incision.

Male genitalia paired. Testes (Fig. 22D) originating in XI, extending forwards into X, in one specimen back into XII, with testis sacs covering mass of irregularly arranged lobes. Sperm funnels in XI, 145-170 µm long, 45-50 µm wide, making them 3-4 times longer than wide, funnels tapering towards vasa deferentia. Most of vasa irregularly coiled in XII, 10 µm wide. Penial bulbs (Fig. 22E) slightly bilobed, 85-120 µm in diameter. Ovaries in XII. Mature eggs not observed.

Spermathecae (Fig. 22C) in V, pouch-shaped. Ectal duct long, gradually widening. Ampulla not clearly set off from duct, entally connecting with oesophagus. No sperm observed. Spermathecae 125-145 µm long, 25-40 µm wide at widest part. Gland cells surrounding ectal pore, divided into several lobes, whole glandular body 35-65 µm in diameter at its widest part. Two midventral subneural glands in XV– XVI, 45-100 µm, 50-65 µm long, respectively.

Geographical distribution.

Genetically identified from Norway.

Remarks.

Initial comparisons found similarities between this species and Lumbricillus westheidei Kossmagk-Stephan, 1983, such as similar shape of spermathecae and slightly bilobed penial bulbs. However, having re-examined Kossmagk-Stephan’s type material we found some important differences compared to our specimens. First, L. westheidei has only two chaetae per bundle, whereas our specimens have up to three chaetae in the preclitellar segments (the position of the upper bundles is identical in the two species). Second, the three pairs of pharyngeal glands are clearly separated in L. westheidei but in our specimens at least the first two pairs appear to have a dorsal connection. Third, the testis sacs of L. westheidei are much smaller than the ones we observed in our specimens. Fourth, the vasa deferentia appear to be much longer and form many more coils in segment XII in L. westheidei compared to our L. sp. H. Finally, the sperm funnels of L. westheidei are about 10 times longer than wide, against the 4:1 length:width ratio observed in our specimens. Unfortunately, none of our examined specimens appeared to be fully mature, as sperm were not observed either at the sperm funnels or in the spermathecae, and there were no mature eggs present. This suggests that the sperm funnels and spermathecae were not fully developed and could at maturity resemble those of L. westheidei more. Due to this uncertainty we cannot completely rule out that our specimens are of the same species as L. westheidei ; however, for now we will continue to treat it as an unknown species, simply referred to as L. sp. H.

Since L. westheidei resembles, in its general morphology, our L. sp. H, it is important to add some notes on its generic allocation. Kossmagk-Stephan (1983) questioned the placement in Lumbricillus due to the undivided testis sacs. He had also observed this feature in some other " Lumbricillus " species, such as L. arenarius and L. semifuscus , the latter here below transferred to Claparedrilus gen. n. Furthermore, he noted a similarity in the morphology of the spermathecae between L. westheidei , L. buelowi , L. knoellneri and L. codensis Lasserre, 1971. In 1985, Coates and Erséus established the new genus Randidrilus and designated Lumbricillus codensis as its type species. Because of the resemblance to the latter in the bilobed penial bulb, the long spermathecal ectal duct, the long sperm funnels and the undivided testis sac, Kossmagk-Stephan (1985) proposed in his doctoral thesis the new combination, R. westheidei , and since then the species was regarded as another member of Randidrilus (Coates, 1989; Mackei and Erséus 1997; Schmelz and Collado 2012). However, we confirm here that, unlike other species of Randidrilus , L. westheidei has more than a single chaeta per bundle, does not lack chaetae in numerous lateral and ventral bundles and does not have an unpaired sperm sac extending backwards into postclitellar segments. Instead, L. westheidei resembles members of the arenarius group within Lumbricillus by having few chaetae, long sperm funnels, slightly bilobed penial bulbs and paired testis sacs that are not regularly lobed. Therefore, we transfer this species back from Randidrilus into Lumbricillus , making it L. westheidei once again.

Lumbricillus sp. H is genetically closely related to L. arenarius and L. dubius (Stephenson, 1911) (Fig. 1).