Lumbricillus finisafricae, Klinth & Rota & Martinsson & Prantoni & Erséus, 2022

Klinth, Mårten J., Rota, Emilia, Martinsson, Svante, Prantoni, Alessandro L. & Erséus, Christer, 2022, New insights into the systematics of Lumbricillus and Marionina (Clitellata: Enchytraeidae) inferred from Southern Hemisphere samples, including three new species, Zoological Journal of the Linnean Society 194 (4), pp. 1103-1133 : 1115-1116

LUMBRICILLUS FINISAFRICAE KLINTH, ROTA & ERSÉUS SP. NOV.

( FIG. 6 )

Z o o b a n k r e g i s t r a t i o n: u r n: l s i d: z o o b a n k. org:act: E7F65CC6-083F-4889-B03B-7DA9137B2665

Holotype: SAMCTypeColl.SAMC-A094448 (CE26170), a mature amputated specimen stained in Paracarmine and mounted on a slide. Leg. Gavin Rishworth, 20 April 2015. COI barcode, GenBank MZ393951 ; accession numbers for additional genetic data are given in Table 1 and the Supporting Information ( Table S1 ).

Type locality: Cape Recife Natural Reserve, Port Elizabeth, South Africa, on stromatolites. 34.0450 S, 25.5689 E.

Etymology: The new species epithet derives from the Latin finis, boundary or end, and the continent Africa, referring to this species being found at the end of Africa.

Diagnosis: This species is a member of the L. lineatus group, meaning that it has testis sacs forming clubshaped lobes arranged in a fan shape, and spindleshaped spermathecae. It can be separated from other species in this group by having penial bulbs bulging into an anterior and a posterior lobe. Lumbricillus sadovskyi Marcus, 1965 has penial bulbs lobed in a similar manner, but which are much smaller, five to six times the diameter of vasa, compared with 12 times for L. finisafricae .

Description: Length of first 28 segments 2.4 mm (fixed, amputated specimen); first 15 segments 1.2 mm long; width at clitellum 0.45 mm. Chaetae sigmoid ( Fig. 6A ). Upper bundles dorsolateral (closer to lateral line than the ventral bundles), with three to four chaetae anterior to clitellum, two to four (five) chaetae in postclitellar segments, at least to XXVIII. Ventral bundles with four to five chaetae anterior to clitellum, three to four chaetae posteriorly. The longest measured chaetae 55 µm long, ~3 µm wide. Epidermis loosely covered with rows of pale gland cells. Clitellum with reticulate pattern of gland cells, extending over XII–1/2XIII, absent ventrally.

Coelomocytes numerous, ~15 µm long; round, oval or spindle shaped; granulated, with distinct nucleus. Paired pharyngeal glands ( Fig. 6B ) present in IV, V and VI; each pair converging dorsally, but connections not discernible. Dorsal vessel originating in XIII, with peristomial bifurcation. Nephridia ~75–90 µm long, not observed in preclitellar segments but in 14/15, 19/20 and further postclitellar segments. Anteseptale small, consisting of funnel only. Postseptale oval, tapering into posteroventral efferent duct. Brain with posterior incision.

Male genitalia paired ( Fig. 6D ). Testes originating in anterior of XI, with testis sacs forming regular clubshaped lobes extending forwards into X and IX. Sperm funnels in XI, 165 µm long, 95 µm wide, making them almost twice as long as wide; funnels tapering towards vasa deferentia. Most of vasa irregularly coiled in XII, 10 µm wide. Penial bulbs bilobed with anterior and posterior lobes, combined into a heart-shaped structure; vasa penetrating through the anterior lobe; whole structure 125 µm in diameter. Ovaries in XII. One mature egg observed.

Spermathecae ( Fig. 6C ) in V, spindle shaped, with ectal duct indistinguishable from the ampulla.Ampulla with sperm filling the lumen and heads of spermatozoa embedded in the walls. Ental part of ampulla seemingly connected with oesophagus. Spermathecae 130 µm long, 65 µm wide at widest part of ampulla. Gland cells surrounding ectal duct, forming compact mass, glandular body 95 µm in diameter at its widest part. No midventral subneural glands observed.

Geographical distribution: Known from the type locality in southernmost South Africa only.

Remarks: We only have one specimen of this species, but found it to be morphologically (and genetically) distinct from other Lumbricillus species. Therefore, it is described as a new species here. Genetically, L. finisafricae is placed in the L. lineatus group (sensu Klinth et al., 2017b), with which it shares morphological characters such as a spindle-shaped spermatheca with ectal gland (but without glands along the ectal duct), regularly lobed testis sacs and three or more chaetae per bundle. However, unlike the other species genetically shown to be part of the L. lineatus group, L. finisafricae has a bilobed penial bulb. There are a few other species of Lumbricillus reported to have bilobed penial bulbs, the one most similar to our South African form being L. sadovskyi . The latter was described from two sites (a beach and an artificial mangrove swamp) in Brazil, and it also has an anterior and a posterior lobe in its penial bulbs. However, L. sadovskyi has a much smaller penial bulb [illustrated by Marcus (1965) as five to six times larger than the diameter of the vasa, whereas our specimen has a bulb 12 times larger than the diameter of the vasa], its chaetae vary from two to eight per bundle, and its spermathecae differ greatly in appearance between the two Brazilian localities, possibly indicating a mixture of two species under the same name. Regardless, although L. sadovskyi is possibly the closest species to our South African specimen, we find it too distinct morphologically and geographically to consider it as conspecific to L. finisafricae . A bilobed penial bulb was reported for ‘ Pachydrilus lineatus ’ sensu Backlund (1947) , but the two lobes were described as dorsal and ventral, whereas L. finisafricae has one anterior and one posterior lobe. Also, in L. incisus (from King George Island) the bilobed bulb is transversely oriented, not longitudinally oriented. There are species in the L. arenarius group with bilobed penial bulbs, but they have three or fewer chaetae per bundle, irregularly lobed testis sacs, and are not closely related genetically to the South African species. The Lumbricillus of Africa are poorly studied, and the few species reported include Lumbricillus mangeri ( Michaelsen, 1914) from Cameroon, which is probably not a Lumbricillus but some form of Marionina s.l., and a record of Lumbricillus verrucosus ( Claparède, 1861) from Namibia ( Michaelsen, 1914), although we cannot say whether this is the same as the L. verrucosus we know from the Northern Hemisphere (see Klinth et al., 2017a, b). None of the aforementioned species is morphologically similar to L. finisafricae .

Figures

Figure 6. Lumbricillus finisafricae, holotype. A, chaetal bundle. B, anterior part of body. C, spermatheca. D, genitalia. Abbreviations are defined under ‘Taxonomy’. Scale bars: 100 μm.