Achaeta koreana, Dózsa-Farkas & Felföldi & Nagy & Hong, 2018

Dózsa-Farkas, Klára, Felföldi, Tamás, Nagy, Hajnalka & Hong, Yong, 2018, New enchytraeid species from Mount Hallasan (Jeju Island, Korea) (Enchytraeidae, Oligochaeta), Zootaxa 4496 (1), pp. 337-381 : 339-343

Achaeta koreana sp. n.

( Figures 1 , 2 , 5A–C )

Type material. Holotype: NIBRIV0000810584 slide No. 2210, adult, stained whole mounted specimen. Type locality: site 4, Baekrokdam crater on the summit of Mt. Hallasan, Jeju Island, Korea, soil of grass on highland in North slope (N 33˚21'46.0", E 126˚31'58.0"), 1843 m elevation, 0 9.06.2016, leg. Y. Hong. Paratypes (in total 9 stained, adult specimens on slides and 37 specimens in 70% ethanol): NIBRIV0000810585, slide No. 2198, site 1, NIBRIV0000811380, slide No. 2276, site 2, P.113.1. slide No. 2212, from type locality, P.113.2.1–113.2.3. slides No . 2193–2195, site 6, P.113.3. slide No. 2196, site 5, P.113.4.1, slides No. 2197, site 1. In 70% ethanol: P.113.5, from type locality 10 specimens; P.113.6 site 2 seven specimens; P.113.7 site 5 eight specimens; P.113.8, site 6 twelve specimens.

Further material examined. 15 specimens investigated in vivo, 3 of them processed for DNA analysis.

Etymology. Named after the country where it was found.

Diagnosis. The new species can be recognized by the following combination of characters: (1) small, stout worms (2–3 mm long and 200–280 µm wide at clitellum in vivo), segments 17–22; (2) no pyriform glands; (3) clitellum developed only laterally: dorso-lateral area with hyalocytes in disordered three or four longitudinal rows; (4) dorsal blood vessel from VI; (5) pharyngeal glands at 4/5–5/6 connected dorsally, at 6/7 separate dorsally, the first ventral lobes separate from the dorsal lobes in IV, secondary ventral glands absent; (6) three pairs of preclitellar nephridia; (7) pars tumida of midgut from XIII–XIV, extending over 2 segments; (8) sperm funnel small, barrel-shaped, collar narrower than funnel body; (9) male pores in XII, ventrolaterally, no glandular body, only the pore surrounded by small inconspicuous glands; (10) spermathecae confined to V.

Description. Small worm ( Fig. 1D ). Holotype 2.8 mm long, 275 µm wide at VIII and 315 µm at clitellum (fixed), 21 segments. Length of paratypes 2.5–3.8 mm, width 200–250 µm at VIII and 220–280 µm at clitellum in vivo, length of fixed specimens 2–3 mm, width 220–270 µm at VIII and 2 30–300 µm at clitellum, segments 17–22. No pyriform glands. Body wall thick, thickness dorsally 22–24 µm, cuticle 4–7 µm, ventrally 17–18 µm and 2–3 µm, respectively, in vivo ( Fig. 1A ). Clitellum in XII–1 /2 XIII developed only laterally, dorso-lateral areas with hyalocytes in two or three disordered longitudinal rows ( Fig. 1C ), hyalocytes large and conspicuous, 28–32 µm high and 17–19 µm wide, granulocytes 20–24 by 16–14 µm ( Fig. 1E ). Ventro-laterally only granulocytes. The dorsal interruption 60–70 µm wide in vivo, dorsal borderline consisting of granular cells only in one longitudinal row ( Fig. 1B ). Ventral borderlines inconspicuous. Head pore on the top of prostomium ( Figs. 1F–G ). Spermathecal pores at 4/ 5 in lateral position. Male pores in XII.

Brain egg-shaped 1.5 times longer than wide, 80–90 µm long, fixed ( Fig. 1F ). The prostomial ganglion ( Figs. 1F,G ) well visible, 37–40 µm long (fixed). Pharyngeal glands at 4/5–6/7 ( Figs. 2A , 5A ), all with ventral lobes. The first and secondary dorsal lobes united dorsally, the third pair separate dorsally. Three pairs of preclitellar nephridia at 6/7–8/9 constricted by septum. Length ratio anteseptale: postseptale 1: 2.5 preclitellarly, postseptale tapers gradually into efferent duct, with small terminal vesicle ( Figs. 2D–E ). Dorsal blood vessel from VI ( Figs. 2A , 5A ). Coelomocytes about 40–53 µm long in vivo, flat, cytoplasm pale, margin with indefinite contour in top view, but spindle-shaped in side view ( Fig. 2C ), the length measurable only in side view. Oesophageal appendages in V, well developed without canal in IV ( Figs. 2A , 5A ). Chloragocytes yellowish-brown, about 15 µm long in vivo. Midgut pars tumida XIII–XIV (occupying 2 segments) ( Fig. 2B ). Sperm funnel small, barrel-shaped, 65–90 µm long in vivo (53–62 µm fixed), about 1.2–2 times longer than wide, collar narrower than funnel body ( Figs. 2F–G , 5C ). Sperm duct 6 µm thick in vivo. Spermatozoa 75–90 µm, heads 30–38 µm long in vivo (52–60 µm and 17–23 µm, fixed). Seminal vesicle absent. Male copulatory organs small, widely separate ventro-laterally, no glandular body or bursa, only the pore surrounded by small inconspicuous glands ( Figs. 2H,I ). Spermathecae small, free, confined to V. The short ectal duct (20–30 µm long 20–23 µm wide in vivo) has a small gland ( Figs. 2L,M ). In welldeveloped specimens the duct widens slightly into a narrow dilation of ampulla (25–28 µm wide). After the dilation the connecting tube (about 60 µm long and 20 µm wide) ends in an elongated globular ental reservoir (35–50 µm long, 25–35 µm wide in vivo) in V. The surface of the reservoir is granulated, sperm is visible only in the ampullar dilation and the connecting tube ( Figs. 2J–L , 5B ).

Distribution and habitat. In Korea, Mt. Hallasan, above 1306 m elevation, at site 1–7.

Differential diagnosis. Among the previously described 12 small Achaeta species without pyriform glands and the spermathecae confined to segments V–VI, none has the origin of the dorsal vessel from VI; moreover, secondary pharyngeal glands are, with one exception ( A. hanagarthi Schmelz, 2008 ), present, and the spermathecal opening is without a small gland. In A. camerani (Cognetti, 1899) the dorsal blood vessel originates in VIII and in the all other species in VII. A. brevivasa Graefe, 1980 , A. diddeni Graefe, 2007 , A. hallensis Möller,1976 , A. antefolliculata Dózsa-Farkas & Boros, 2005 , A. afolliculata S esma & Dózsa-Farkas, 1993 and A. singularis Schmelz, 2008 have two pairs of preclitellar nephridia, further A. hanagarthi and A. paranensis Schmelz, 2008 have only one pair. Only A. pannonica Graefe, 1989 , A. iberica Graefe, 1989 and A. etrusca Rota, 1995 similarly to A. koreana sp. n. have three pairs of preclitellar nephridia, as in the new species. But in A. pannonica all reproductive organs except the spermathecae are shifted one segment forward, so the male pores are in XI, while in the new species, in A. iberica and in A. etrusca they are in the usual position in XII. A. etrusca differs from A. koreana sp. n. by his paired knob-like cutaneous gland structures dorsolateral in II–VI and by the shorter spermatozoa (40 µm long, sperm heads 15 µm ( Rota 2015) vs. 75–90 µm and 30–38 µm, respectively), moreover the penial bulbs are compact. Finally, in A. iberica , hyalocytes of the clitellar glands are lined in 4 distinct longitudinal rows.

Figures

FIGURE 1. Micrographs of Achaeta koreana sp. n. A. Thick cuticle terminally dorsally thicker (white arrow) than ventrally (black arrow). B. Clitellar glands, dorsal view (interruption marked with arrow). C. Clitellar glands, lateral view (arrows: hyaline glands). D. Entire individual (head marked with arrow). E. Clitellar glands, lateral view. F–G. Head (white arrows: head pore; black arrows: prostomial ganglia; b=brain, ph=pharynx). A–E, G in vivo, F fixed, stained. Scale bars A–D, F, G 50 µm; E 20 µm).

FIGURE 2. Micrographs of Achaeta koreana sp. n. A. Pharyngeal glands, lateral view (marked with arrows, o= oesophageal appendage, dv= dorsal vessel, n=first nephridium). B. Midgut pars tumida XIII–XV. C. Coelomocytes. D. First nephridium. E. Nephridium terminally. F–G. Sperm funnels. H. Clitellar glands, lateral view (arrow: male opening). I. Male opening with small surrounding glands (arrow). J–L. Spermathecae (arrow in L: ectal gland). M. Spermathecal ectal gland (marked with arrow). A–G, I–M in vivo, H fixed, stained. Scale bars A–H, J–L 50 µm; I, M 20 µm.

FIGURE 5. Achaeta koreana sp. n. (A–C), Achaeta macroampullacea sp. n. (D–E), Bryodrilus hallasanensis sp. n. (F), Enchytronia seongpanakiensis sp. n. (G) and Chaemaedrilus baekrokdamensis sp. n. (H) A. Pharyngeal glands (dv=dorsal vessel, oesophageal appendages marked with arrows). B. Spermatheca. C. Sperm funnel. D. Male copulatory organ and granulocytes at ventral border of clitellum, E-H. Spermathecae. Scale bars 50 µm.