Globulidrilus helgei, Christensen & Dózsa-Farkas, 2012

Christensen, Bent & Dózsa-Farkas, Klára, 2012, A new genus Globulidrilus and three new enchytraeid species (Oligochaeta: Enchytraeidae) from Seoraksan National Park (Korea), Journal of Natural History 46 (45 - 46), pp. 2769-2785 : 2771-2777

Globulidrilus helgei sp. nov.

( Figures 1 , 2 , 3 , 4C )

Type material

Holotype. G.1. slide No. 526, adult specimen, whole-mounted.

Type locality. Korea, Seoraksan National park. Abundant in a particularly moist spot rich in decaying organic matter. For further details see Material and methods.

Paratypes. P. 91. 1–10 slide No. 527, 531, 532, 533, 534, 535, 557, 566, 567, 568. All worms adult except on slide 535 (a subadult specimen, without eggs). All collection data are in holotype.

Etymology

Named in honour of the collector.

Description

Slender medium-sized reddish worm. Holotype 8.95 mm long, 340 µm wide at VIII and 390 µm at the clitellum (fixed), segments 36. Body length of paratypes 6–15 mm, width 240–350 µm at VIII and 300–440 µm at the clitellum (in vivo), length of fixed specimens 6.7–9.7 mm, width 250–310 µm at VIII, 290–410 µm at the clitellum, segments 31–37. Chaetae ( Figure 2A–B ) sigmoid without nodulus, 2,3,(1)–2(1,0):2,3,4(1,0)–2(3), about 55–65 µm long and 5 µm wide, in posterior segments slightly longer, absent in XII. Head pore at 0/I inconspicuous; dorsal pores absent. Hyaline epidermal gland cells arranged in 2–3 transverse rows, rarely slightly pigmented in anterior segments.

Clitellum in XII–1/3XIII, hyalocytes and granulocytes in dense rows, granulocytes dominate dorsally (the size of hyalocytes and granulocytes about the same, 11–17 × 10–12 µm, fixed) ( Figure 2C ), glands absent anteroventrally and between the penial bulbs but present posteroventrally ( Figure 2D ). Body wall 18–25 µm thick, cuticle 2.0–2.5 µm (fixed). Brain ( Figure 1A ) convex anteriorly and deeply incised posteriorly, about 170–200 µm long (fixed), 2–3 times longer than wide.

The two anterior pharyngeal glands in IV and V with well-developed ventral lobes but not united dorsally, the third pair in VI small, often with ventral lobes only, and sometimes even absent ( Figure 1C ). Chloragocytes weakly developed. Dorsal blood vessel originates in XIV–XV, the anterior bifurcation in I, blood reddish ( Figure 2E ).

Preclitellar nephridia from 6/7 to 9/10, four pairs, the two posterior often enlarged, anteseptale funnel and a few coils of the nephridial canal, postseptale much larger, the ectally leading canal arises near the septum but remains attached to the ventral side of the postseptale until sub-terminally ( Figures 1B and 3A ), the canal widens abruptly near the outer opening, diameter of these vesicles about 25 µm ( Figures 3B and 4C ). Coelomocytes ( Figure 2F ) oval, wavy outline with fine hyaline plasma threads, 20–37 µm long (fixed) usually congregated in IV – V. Seminal vesicle absent. Sperm funnels ( Figures 1F and 3C ) 100–190 µm long and 30–40 µm wide, about 4–6 times as long as wide (fixed), collar of same width as the funnel itself, often bend backwards, sperm ducts very long and slender, about 3.5 µm wide (fixed), irregularly coiled in XII. Spermatozoa about 120–140 µm long, head 40–60 µm (in vivo) and 90 µm and 30 µm (fixed). Male copulatory organs ( Figures 2D and 3D ) small rounded compact penial bulbs, diameter 40–55 µm (fixed). No subneural glands, but approximately half the specimens have accessory sexual glands in XI or in XI and XIII: holotype (slide 526) in XI (87 × 50µm); paratype (slide 535) in XI (87 × 67µm) and in XIII (92 × 87µm), paratype (slide 534) two close glands in XI (85 × 55 and 85 × 45µm) and one in XIII (90 × 65µm) ( Figure 3D ). Ectal duct of spermatheca devoid of glands along its length (140–200 µm), diameter near ectal opening 10–12 µm, gradually increasing entally (up to 22.5 µm). Ampulla thin-walled and onion-shaped, diameter 40–60 µm, sperm arranged in 1–4 regular bundles (diameter 20–27 µm) located near the outer opening and only occupying a smaller part of the lumen. Both ampullae attached to the oesophagus separately, by a narrow strand of tissue but without any open connection ( Figures 1D–E and 3E–F ). Simultaneously one to two mature eggs .

Distribution and habitat

Only known from the type locality.

Remarks

Marionina riparia Bretscher, 1899 , a freshwater species with worldwide distribution, fits the aforementioned description of the new genus Globulidrilus , and hence we suggest to include this species in the new genus, as Globulidrilus riparius ( Bretscher, 1899) . The comparison of G. helgei and G. riparius , however, is not straightforward because of taxonomic problems in the latter. The poor original description of M. riparia in Bretscher (1899) was first emended by Černosvitov (1937) and later by Nielsen and Christensen (1959), but these subsequent accounts, which were based on different material, increased the range of variation of taxonomic characters. In fact, if all descriptions and redescriptions of M. riparia are considered, G. helgei may be included in G. riparius sensu lato, but we believe that such a broadly conceived taxon comprises several species, following Timm (2007). In Table 2 and in Figures 4A,B,D–F we present the variant of G. riparius that in our experience is the most common one in Europe, and here differences to G. helgei are clear-cut and beyond doubt. Thus the genus Globulidrilus comprises at least two species, but possibly more. For the time being, we retain the name G. riparius for the variant outlined here. A taxonomic revision of G. riparius sensu lato is urgently needed but beyond the scope of this article. Since type material is lacking, re-sampling of the type and reference localities will be necessary, and the problem should be addressed with morphological and molecular methods. Finally the name riparius may have an older synonym with nomenclatural priority ( Timm 2007; Schmelz and Collado 2010).

as conceived here.

Figures

Figure 1. Globulidrilus helgei sp.nov. (A) Brain; (B) nephridium; (C) pharyngeal glands; (D) spermatheca with one sperm bundle; (E) Spermatheca with three sperm bundles; (F) sperm funnel.

Figure 2. Globulidrilus helgei sp.nov. micrographs from stained whole-mounts. (A) Ventral anteclitellar chaetae; (B) ventral postclitellar chaetae; (C) clitellar glands, dorsal view; (D) clitellar glands almost absent ventrally (only present along the posterior margin); (E) anterior bifurcation of the dorsal vessel in I; (F) coelomocytes.

Figure 3. Globulidrilus helgei sp.nov. micrographs from a living worm (A) and stained wholemounts (B–F). (A) Nephridium in the postclitellar region; (B) nephridium in XXVI (the large swelling at the ectal opening marked with arrow); (C) sperm funnels (marked with arrows); (D) clitellar region, ventral view (male opening marked with white arrows, accessory sexual glands at 11/12 and 12/13 marked with black arrows; (E and F) spermathecae marked with arrows. Notes: sf, sperm funnel; phg, pharyngeal glands.

Figure 4. Globulidrilus riparius micrographs from living worms (A–B) and from stained wholemounts (D–F), and Globulidrilus helgei sp. nov. micrograph from stained whole-mount (C). (A) Nephridium at 7/8 (marked with arrow); (B) coelomocytes (the fine hyaline plasma threads marked with arrow); (C and D) difference in size between the two species of the swelling at the ectal opening of the nephridia (marked with arrows); (E) head pore (marked with arrow) coelomocytes coming out; (F) spermathecae marked with black arrows, the glands at the ectal opening marked with white arrows.